Merge commit '6eba9cd92c295c5389944f6adda1f1e83b2cb008' as 'subprojects/thiserror'

118 files changed, 6352 insertions, 0 deletions

diff --git a/subprojects/thiserror/.github/FUNDING.yml b/subprojects/thiserror/.github/FUNDING.yml
new file mode 100644
index 0000000..7507077
--- /dev/null
+++ b/subprojects/thiserror/.github/FUNDING.yml
@@ -0,0 +1 @@
+github: dtolnay
diff --git a/subprojects/thiserror/.github/workflows/ci.yml b/subprojects/thiserror/.github/workflows/ci.yml
new file mode 100644
index 0000000..8320187
--- /dev/null
+++ b/subprojects/thiserror/.github/workflows/ci.yml
@@ -0,0 +1,128 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+  schedule: [cron: "40 1 * * *"]
+
+permissions:
+  contents: read
+
+env:
+  RUSTFLAGS: -Dwarnings
+
+jobs:
+  pre_ci:
+    uses: dtolnay/.github/.github/workflows/pre_ci.yml@master
+
+  test:
+    name: Rust ${{matrix.rust}}
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        rust: [nightly, beta, stable, 1.81.0, 1.76.0]
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{matrix.rust}}
+          components: rust-src
+      - name: Enable type layout randomization
+        run: echo RUSTFLAGS=${RUSTFLAGS}\ -Zrandomize-layout >> $GITHUB_ENV
+        if: matrix.rust == 'nightly'
+      - name: Enable nightly-only tests
+        run: echo RUSTFLAGS=${RUSTFLAGS}\ --cfg=thiserror_nightly_testing >> $GITHUB_ENV
+        if: matrix.rust == 'nightly'
+      - run: cargo test --workspace --exclude thiserror_no_std_test
+      - run: cargo test --manifest-path tests/no-std/Cargo.toml
+        if: matrix.rust != '1.76.0'
+      - run: cargo test --no-default-features
+      - uses: actions/upload-artifact@v4
+        if: matrix.rust == 'nightly' && always()
+        with:
+          name: Cargo.lock
+          path: Cargo.lock
+        continue-on-error: true
+
+  msrv:
+    name: Rust 1.68.0
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@1.68.0
+        with:
+          components: rust-src
+      - run: cargo check
+
+  minimal:
+    name: Minimal versions
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@nightly
+      - run: cargo generate-lockfile -Z minimal-versions
+      - run: cargo check --locked
+
+  doc:
+    name: Documentation
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    env:
+      RUSTDOCFLAGS: -Dwarnings
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: rust-src
+      - uses: dtolnay/install@cargo-docs-rs
+      - run: cargo docs-rs
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request'
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: clippy, rust-src
+      - run: cargo clippy --tests --workspace -- -Dclippy::all -Dclippy::pedantic
+
+  miri:
+    name: Miri
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@miri
+      - run: cargo miri setup
+      - run: cargo miri test
+        env:
+          MIRIFLAGS: -Zmiri-strict-provenance
+
+  outdated:
+    name: Outdated
+    runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request'
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v5
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/install@cargo-outdated
+      - run: cargo outdated --workspace --exit-code 1
diff --git a/subprojects/thiserror/.gitignore b/subprojects/thiserror/.gitignore
new file mode 100644
index 0000000..e9e2199
--- /dev/null
+++ b/subprojects/thiserror/.gitignore
@@ -0,0 +1,2 @@
+/target/
+/Cargo.lock
diff --git a/subprojects/thiserror/Cargo.toml b/subprojects/thiserror/Cargo.toml
new file mode 100644
index 0000000..a4364bd
--- /dev/null
+++ b/subprojects/thiserror/Cargo.toml
@@ -0,0 +1,50 @@
+[package]
+name = "thiserror"
+version = "2.0.17"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+categories = ["rust-patterns", "no-std"]
+description = "derive(Error)"
+documentation = "https://docs.rs/thiserror"
+edition = "2021"
+keywords = ["error", "error-handling", "derive"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/dtolnay/thiserror"
+rust-version = "1.68"
+
+[features]
+default = ["std"]
+
+# Std feature enables support for formatting std::path::{Path, PathBuf}
+# conveniently in an error message.
+#
+#     #[derive(Error, Debug)]
+#     #[error("failed to create configuration file {path}")]
+#     pub struct MyError {
+#         pub path: PathBuf,
+#         pub source: std::io::Error,
+#     }
+#
+# Without std, this would need to be written #[error("... {}", path.display())].
+std = []
+
+[dependencies]
+thiserror-impl = { version = "=2.0.17", path = "impl" }
+
+[dev-dependencies]
+anyhow = "1.0.73"
+ref-cast = "1.0.18"
+rustversion = "1.0.13"
+trybuild = { version = "1.0.108", features = ["diff"] }
+
+[workspace]
+members = ["impl", "tests/no-std"]
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+rustdoc-args = [
+    "--generate-link-to-definition",
+    "--generate-macro-expansion",
+    "--extern-html-root-url=core=https://doc.rust-lang.org",
+    "--extern-html-root-url=alloc=https://doc.rust-lang.org",
+    "--extern-html-root-url=std=https://doc.rust-lang.org",
+]
diff --git a/subprojects/thiserror/LICENSE-APACHE b/subprojects/thiserror/LICENSE-APACHE
new file mode 100644
index 0000000..1b5ec8b
--- /dev/null
+++ b/subprojects/thiserror/LICENSE-APACHE
@@ -0,0 +1,176 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+1. Definitions.
+
+   "License" shall mean the terms and conditions for use, reproduction,
+   and distribution as defined by Sections 1 through 9 of this document.
+
+   "Licensor" shall mean the copyright owner or entity authorized by
+   the copyright owner that is granting the License.
+
+   "Legal Entity" shall mean the union of the acting entity and all
+   other entities that control, are controlled by, or are under common
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+   "control" means (i) the power, direct or indirect, to cause the
+   direction or management of such entity, whether by contract or
+   otherwise, or (ii) ownership of fifty percent (50%) or more of the
+   outstanding shares, or (iii) beneficial ownership of such entity.
+
+   "You" (or "Your") shall mean an individual or Legal Entity
+   exercising permissions granted by this License.
+
+   "Source" form shall mean the preferred form for making modifications,
+   including but not limited to software source code, documentation
+   source, and configuration files.
+
+   "Object" form shall mean any form resulting from mechanical
+   transformation or translation of a Source form, including but
+   not limited to compiled object code, generated documentation,
+   and conversions to other media types.
+
+   "Work" shall mean the work of authorship, whether in Source or
+   Object form, made available under the License, as indicated by a
+   copyright notice that is included in or attached to the work
+   (an example is provided in the Appendix below).
+
+   "Derivative Works" shall mean any work, whether in Source or Object
+   form, that is based on (or derived from) the Work and for which the
+   editorial revisions, annotations, elaborations, or other modifications
+   represent, as a whole, an original work of authorship. For the purposes
+   of this License, Derivative Works shall not include works that remain
+   separable from, or merely link (or bind by name) to the interfaces of,
+   the Work and Derivative Works thereof.
+
+   "Contribution" shall mean any work of authorship, including
+   the original version of the Work and any modifications or additions
+   to that Work or Derivative Works thereof, that is intentionally
+   submitted to Licensor for inclusion in the Work by the copyright owner
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+   communication on electronic mailing lists, source code control systems,
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+   designated in writing by the copyright owner as "Not a Contribution."
+
+   "Contributor" shall mean Licensor and any individual or Legal Entity
+   on behalf of whom a Contribution has been received by Licensor and
+   subsequently incorporated within the Work.
+
+2. Grant of Copyright License. Subject to the terms and conditions of
+   this License, each Contributor hereby grants to You a perpetual,
+   worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+   copyright license to reproduce, prepare Derivative Works of,
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+   Work and such Derivative Works in Source or Object form.
+
+3. Grant of Patent License. Subject to the terms and conditions of
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+   (except as stated in this section) patent license to make, have made,
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+   where such license applies only to those patent claims licensable
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+   Contribution(s) alone or by combination of their Contribution(s)
+   with the Work to which such Contribution(s) was submitted. If You
+   institute patent litigation against any entity (including a
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+   or a Contribution incorporated within the Work constitutes direct
+   or contributory patent infringement, then any patent licenses
+   granted to You under this License for that Work shall terminate
+   as of the date such litigation is filed.
+
+4. Redistribution. You may reproduce and distribute copies of the
+   Work or Derivative Works thereof in any medium, with or without
+   modifications, and in Source or Object form, provided that You
+   meet the following conditions:
+
+   (a) You must give any other recipients of the Work or
+       Derivative Works a copy of this License; and
+
+   (b) You must cause any modified files to carry prominent notices
+       stating that You changed the files; and
+
+   (c) You must retain, in the Source form of any Derivative Works
+       that You distribute, all copyright, patent, trademark, and
+       attribution notices from the Source form of the Work,
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+       the Derivative Works; and
+
+   (d) If the Work includes a "NOTICE" text file as part of its
+       distribution, then any Derivative Works that You distribute must
+       include a readable copy of the attribution notices contained
+       within such NOTICE file, excluding those notices that do not
+       pertain to any part of the Derivative Works, in at least one
+       of the following places: within a NOTICE text file distributed
+       as part of the Derivative Works; within the Source form or
+       documentation, if provided along with the Derivative Works; or,
+       within a display generated by the Derivative Works, if and
+       wherever such third-party notices normally appear. The contents
+       of the NOTICE file are for informational purposes only and
+       do not modify the License. You may add Your own attribution
+       notices within Derivative Works that You distribute, alongside
+       or as an addendum to the NOTICE text from the Work, provided
+       that such additional attribution notices cannot be construed
+       as modifying the License.
+
+   You may add Your own copyright statement to Your modifications and
+   may provide additional or different license terms and conditions
+   for use, reproduction, or distribution of Your modifications, or
+   for any such Derivative Works as a whole, provided Your use,
+   reproduction, and distribution of the Work otherwise complies with
+   the conditions stated in this License.
+
+5. Submission of Contributions. Unless You explicitly state otherwise,
+   any Contribution intentionally submitted for inclusion in the Work
+   by You to the Licensor shall be under the terms and conditions of
+   this License, without any additional terms or conditions.
+   Notwithstanding the above, nothing herein shall supersede or modify
+   the terms of any separate license agreement you may have executed
+   with Licensor regarding such Contributions.
+
+6. Trademarks. This License does not grant permission to use the trade
+   names, trademarks, service marks, or product names of the Licensor,
+   except as required for reasonable and customary use in describing the
+   origin of the Work and reproducing the content of the NOTICE file.
+
+7. Disclaimer of Warranty. Unless required by applicable law or
+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+   implied, including, without limitation, any warranties or conditions
+   of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+   PARTICULAR PURPOSE. You are solely responsible for determining the
+   appropriateness of using or redistributing the Work and assume any
+   risks associated with Your exercise of permissions under this License.
+
+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
+   incidental, or consequential damages of any character arising as a
+   result of this License or out of the use or inability to use the
+   Work (including but not limited to damages for loss of goodwill,
+   work stoppage, computer failure or malfunction, or any and all
+   other commercial damages or losses), even if such Contributor
+   has been advised of the possibility of such damages.
+
+9. Accepting Warranty or Additional Liability. While redistributing
+   the Work or Derivative Works thereof, You may choose to offer,
+   and charge a fee for, acceptance of support, warranty, indemnity,
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+   on Your own behalf and on Your sole responsibility, not on behalf
+   of any other Contributor, and only if You agree to indemnify,
+   defend, and hold each Contributor harmless for any liability
+   incurred by, or claims asserted against, such Contributor by reason
+   of your accepting any such warranty or additional liability.
+
+END OF TERMS AND CONDITIONS
diff --git a/subprojects/thiserror/LICENSE-MIT b/subprojects/thiserror/LICENSE-MIT
new file mode 100644
index 0000000..31aa793
--- /dev/null
+++ b/subprojects/thiserror/LICENSE-MIT
@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/subprojects/thiserror/README.md b/subprojects/thiserror/README.md
new file mode 100644
index 0000000..f05e2ec
--- /dev/null
+++ b/subprojects/thiserror/README.md
@@ -0,0 +1,238 @@
+derive(Error)
+=============
+
+[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/thiserror-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/thiserror)
+[<img alt="crates.io" src="https://img.shields.io/crates/v/thiserror.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/thiserror)
+[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-thiserror-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/thiserror)
+[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/thiserror/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/thiserror/actions?query=branch%3Amaster)
+
+This library provides a convenient derive macro for the standard library's
+[`std::error::Error`] trait.
+
+[`std::error::Error`]: https://doc.rust-lang.org/std/error/trait.Error.html
+
+```toml
+[dependencies]
+thiserror = "2"
+```
+
+*Compiler support: requires rustc 1.68+*
+
+<br>
+
+## Example
+
+```rust
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum DataStoreError {
+    #[error("data store disconnected")]
+    Disconnect(#[from] io::Error),
+    #[error("the data for key `{0}` is not available")]
+    Redaction(String),
+    #[error("invalid header (expected {expected:?}, found {found:?})")]
+    InvalidHeader {
+        expected: String,
+        found: String,
+    },
+    #[error("unknown data store error")]
+    Unknown,
+}
+```
+
+<br>
+
+## Details
+
+- Thiserror deliberately does not appear in your public API. You get the same
+  thing as if you had written an implementation of `std::error::Error` by hand,
+  and switching from handwritten impls to thiserror or vice versa is not a
+  breaking change.
+
+- Errors may be enums, structs with named fields, tuple structs, or unit
+  structs.
+
+- A `Display` impl is generated for your error if you provide `#[error("...")]`
+  messages on the struct or each variant of your enum, as shown above in the
+  example.
+
+  The messages support a shorthand for interpolating fields from the error.
+
+    - `#[error("{var}")]`&ensp;⟶&ensp;`write!("{}", self.var)`
+    - `#[error("{0}")]`&ensp;⟶&ensp;`write!("{}", self.0)`
+    - `#[error("{var:?}")]`&ensp;⟶&ensp;`write!("{:?}", self.var)`
+    - `#[error("{0:?}")]`&ensp;⟶&ensp;`write!("{:?}", self.0)`
+
+  These shorthands can be used together with any additional format args, which
+  may be arbitrary expressions. For example:
+
+  ```rust
+  #[derive(Error, Debug)]
+  pub enum Error {
+      #[error("invalid rdo_lookahead_frames {0} (expected < {max})", max = i32::MAX)]
+      InvalidLookahead(u32),
+  }
+  ```
+
+  If one of the additional expression arguments needs to refer to a field of the
+  struct or enum, then refer to named fields as `.var` and tuple fields as `.0`.
+
+  ```rust
+  #[derive(Error, Debug)]
+  pub enum Error {
+      #[error("first letter must be lowercase but was {:?}", first_char(.0))]
+      WrongCase(String),
+      #[error("invalid index {idx}, expected at least {} and at most {}", .limits.lo, .limits.hi)]
+      OutOfBounds { idx: usize, limits: Limits },
+  }
+  ```
+
+- A `From` impl is generated for each variant that contains a `#[from]`
+  attribute.
+
+  The variant using `#[from]` must not contain any other fields beyond the
+  source error (and possibly a backtrace &mdash; see below). Usually `#[from]`
+  fields are unnamed, but `#[from]` is allowed on a named field too.
+
+  ```rust
+  #[derive(Error, Debug)]
+  pub enum MyError {
+      Io(#[from] io::Error),
+      Glob(#[from] globset::Error),
+  }
+  ```
+
+- The Error trait's `source()` method is implemented to return whichever field
+  has a `#[source]` attribute or is named `source`, if any. This is for
+  identifying the underlying lower level error that caused your error.
+
+  The `#[from]` attribute always implies that the same field is `#[source]`, so
+  you don't ever need to specify both attributes.
+
+  Any error type that implements `std::error::Error` or dereferences to `dyn
+  std::error::Error` will work as a source.
+
+  ```rust
+  #[derive(Error, Debug)]
+  pub struct MyError {
+      msg: String,
+      #[source]  // optional if field name is `source`
+      source: anyhow::Error,
+  }
+  ```
+
+- The Error trait's `provide()` method is implemented to provide whichever field
+  has a type named `Backtrace`, if any, as a `std::backtrace::Backtrace`. Using
+  `Backtrace` in errors requires a nightly compiler with Rust version 1.73 or
+  newer.
+
+  ```rust
+  use std::backtrace::Backtrace;
+
+  #[derive(Error, Debug)]
+  pub struct MyError {
+      msg: String,
+      backtrace: Backtrace,  // automatically detected
+  }
+  ```
+
+- If a field is both a source (named `source`, or has `#[source]` or `#[from]`
+  attribute) *and* is marked `#[backtrace]`, then the Error trait's `provide()`
+  method is forwarded to the source's `provide` so that both layers of the error
+  share the same backtrace. The `#[backtrace]` attribute requires a nightly
+  compiler with Rust version 1.73 or newer.
+
+
+  ```rust
+  #[derive(Error, Debug)]
+  pub enum MyError {
+      Io {
+          #[backtrace]
+          source: io::Error,
+      },
+  }
+  ```
+
+- For variants that use `#[from]` and also contain a `Backtrace` field, a
+  backtrace is captured from within the `From` impl.
+
+  ```rust
+  #[derive(Error, Debug)]
+  pub enum MyError {
+      Io {
+          #[from]
+          source: io::Error,
+          backtrace: Backtrace,
+      },
+  }
+  ```
+
+- Errors may use `error(transparent)` to forward the source and Display methods
+  straight through to an underlying error without adding an additional message.
+  This would be appropriate for enums that need an "anything else" variant.
+
+  ```rust
+  #[derive(Error, Debug)]
+  pub enum MyError {
+      ...
+
+      #[error(transparent)]
+      Other(#[from] anyhow::Error),  // source and Display delegate to anyhow::Error
+  }
+  ```
+
+  Another use case is hiding implementation details of an error representation
+  behind an opaque error type, so that the representation is able to evolve
+  without breaking the crate's public API.
+
+  ```rust
+  // PublicError is public, but opaque and easy to keep compatible.
+  #[derive(Error, Debug)]
+  #[error(transparent)]
+  pub struct PublicError(#[from] ErrorRepr);
+
+  impl PublicError {
+      // Accessors for anything we do want to expose publicly.
+  }
+
+  // Private and free to change across minor version of the crate.
+  #[derive(Error, Debug)]
+  enum ErrorRepr {
+      ...
+  }
+  ```
+
+- See also the [`anyhow`] library for a convenient single error type to use in
+  application code.
+
+  [`anyhow`]: https://github.com/dtolnay/anyhow
+
+<br>
+
+## Comparison to anyhow
+
+Use thiserror if you care about designing your own dedicated error type(s) so
+that the caller receives exactly the information that you choose in the event of
+failure. This most often applies to library-like code. Use [Anyhow] if you don't
+care what error type your functions return, you just want it to be easy. This is
+common in application-like code.
+
+[Anyhow]: https://github.com/dtolnay/anyhow
+
+<br>
+
+#### License
+
+<sup>
+Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
+2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
+</sup>
+
+<br>
+
+<sub>
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
+be dual licensed as above, without any additional terms or conditions.
+</sub>
diff --git a/subprojects/thiserror/build.rs b/subprojects/thiserror/build.rs
new file mode 100644
index 0000000..d1558fb
--- /dev/null
+++ b/subprojects/thiserror/build.rs
@@ -0,0 +1,195 @@
+use std::env;
+use std::ffi::OsString;
+use std::fs;
+use std::io::ErrorKind;
+use std::iter;
+use std::path::{Path, PathBuf};
+use std::process::{self, Command, Stdio};
+use std::str;
+
+const PRIVATE: &str = "\
+#[doc(hidden)]
+pub mod __private$$ {
+    #[doc(hidden)]
+    pub use crate::private::*;
+}
+";
+
+fn main() {
+    println!("cargo:rerun-if-changed=build/probe.rs");
+
+    println!("cargo:rustc-check-cfg=cfg(error_generic_member_access)");
+    println!("cargo:rustc-check-cfg=cfg(thiserror_nightly_testing)");
+    println!("cargo:rustc-check-cfg=cfg(thiserror_no_backtrace_type)");
+
+    let out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
+    let patch_version = env::var("CARGO_PKG_VERSION_PATCH").unwrap();
+    let module = PRIVATE.replace("$$", &patch_version);
+    fs::write(out_dir.join("private.rs"), module).unwrap();
+
+    let error_generic_member_access;
+    let consider_rustc_bootstrap;
+    if compile_probe(false) {
+        // This is a nightly or dev compiler, so it supports unstable features
+        // regardless of RUSTC_BOOTSTRAP. No need to rerun build script if
+        // RUSTC_BOOTSTRAP is changed.
+        error_generic_member_access = true;
+        consider_rustc_bootstrap = false;
+    } else if let Some(rustc_bootstrap) = env::var_os("RUSTC_BOOTSTRAP") {
+        if compile_probe(true) {
+            // This is a stable or beta compiler for which the user has set
+            // RUSTC_BOOTSTRAP to turn on unstable features. Rerun build script
+            // if they change it.
+            error_generic_member_access = true;
+            consider_rustc_bootstrap = true;
+        } else if rustc_bootstrap == "1" {
+            // This compiler does not support the generic member access API in
+            // the form that thiserror expects. No need to pay attention to
+            // RUSTC_BOOTSTRAP.
+            error_generic_member_access = false;
+            consider_rustc_bootstrap = false;
+        } else {
+            // This is a stable or beta compiler for which RUSTC_BOOTSTRAP is
+            // set to restrict the use of unstable features by this crate.
+            error_generic_member_access = false;
+            consider_rustc_bootstrap = true;
+        }
+    } else {
+        // Without RUSTC_BOOTSTRAP, this compiler does not support the generic
+        // member access API in the form that thiserror expects, but try again
+        // if the user turns on unstable features.
+        error_generic_member_access = false;
+        consider_rustc_bootstrap = true;
+    }
+
+    if error_generic_member_access {
+        println!("cargo:rustc-cfg=error_generic_member_access");
+    }
+
+    if consider_rustc_bootstrap {
+        println!("cargo:rerun-if-env-changed=RUSTC_BOOTSTRAP");
+    }
+
+    // core::error::Error stabilized in Rust 1.81
+    // https://blog.rust-lang.org/2024/09/05/Rust-1.81.0.html#coreerrorerror
+    let rustc = rustc_minor_version();
+    if cfg!(not(feature = "std")) && rustc.map_or(false, |rustc| rustc < 81) {
+        println!("cargo:rustc-cfg=feature=\"std\"");
+    }
+
+    let Some(rustc) = rustc else {
+        return;
+    };
+
+    // std::backtrace::Backtrace stabilized in Rust 1.65
+    // https://blog.rust-lang.org/2022/11/03/Rust-1.65.0.html#stabilized-apis
+    if rustc < 65 {
+        println!("cargo:rustc-cfg=thiserror_no_backtrace_type");
+    }
+}
+
+fn compile_probe(rustc_bootstrap: bool) -> bool {
+    if env::var_os("RUSTC_STAGE").is_some() {
+        // We are running inside rustc bootstrap. This is a highly non-standard
+        // environment with issues such as:
+        //
+        //     https://github.com/rust-lang/cargo/issues/11138
+        //     https://github.com/rust-lang/rust/issues/114839
+        //
+        // Let's just not use nightly features here.
+        return false;
+    }
+
+    let rustc = cargo_env_var("RUSTC");
+    let out_dir = cargo_env_var("OUT_DIR");
+    let out_subdir = Path::new(&out_dir).join("probe");
+    let probefile = Path::new("build").join("probe.rs");
+
+    if let Err(err) = fs::create_dir(&out_subdir) {
+        if err.kind() != ErrorKind::AlreadyExists {
+            eprintln!("Failed to create {}: {}", out_subdir.display(), err);
+            process::exit(1);
+        }
+    }
+
+    let rustc_wrapper = env::var_os("RUSTC_WRAPPER").filter(|wrapper| !wrapper.is_empty());
+    let rustc_workspace_wrapper =
+        env::var_os("RUSTC_WORKSPACE_WRAPPER").filter(|wrapper| !wrapper.is_empty());
+    let mut rustc = rustc_wrapper
+        .into_iter()
+        .chain(rustc_workspace_wrapper)
+        .chain(iter::once(rustc));
+    let mut cmd = Command::new(rustc.next().unwrap());
+    cmd.args(rustc);
+
+    if !rustc_bootstrap {
+        cmd.env_remove("RUSTC_BOOTSTRAP");
+    }
+
+    cmd.stderr(Stdio::null())
+        .arg("--edition=2018")
+        .arg("--crate-name=thiserror")
+        .arg("--crate-type=lib")
+        .arg("--cap-lints=allow")
+        .arg("--emit=dep-info,metadata")
+        .arg("--out-dir")
+        .arg(&out_subdir)
+        .arg(probefile);
+
+    if let Some(target) = env::var_os("TARGET") {
+        cmd.arg("--target").arg(target);
+    }
+
+    // If Cargo wants to set RUSTFLAGS, use that.
+    if let Ok(rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {
+        if !rustflags.is_empty() {
+            for arg in rustflags.split('\x1f') {
+                cmd.arg(arg);
+            }
+        }
+    }
+
+    let success = match cmd.status() {
+        Ok(status) => status.success(),
+        Err(_) => false,
+    };
+
+    // Clean up to avoid leaving nondeterministic absolute paths in the dep-info
+    // file in OUT_DIR, which causes nonreproducible builds in build systems
+    // that treat the entire OUT_DIR as an artifact.
+    if let Err(err) = fs::remove_dir_all(&out_subdir) {
+        // libc::ENOTEMPTY
+        // Some filesystems (NFSv3) have timing issues under load where '.nfs*'
+        // dummy files can continue to get created for a short period after the
+        // probe command completes, breaking remove_dir_all.
+        // To be replaced with ErrorKind::DirectoryNotEmpty (Rust 1.83+).
+        const ENOTEMPTY: i32 = 39;
+
+        if !(err.kind() == ErrorKind::NotFound
+            || (cfg!(target_os = "linux") && err.raw_os_error() == Some(ENOTEMPTY)))
+        {
+            eprintln!("Failed to clean up {}: {}", out_subdir.display(), err);
+            process::exit(1);
+        }
+    }
+
+    success
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = cargo_env_var("RUSTC");
+    let output = Command::new(rustc).arg("--version").output().ok()?;
+    let version = str::from_utf8(&output.stdout).ok()?;
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+    pieces.next()?.parse().ok()
+}
+
+fn cargo_env_var(key: &str) -> OsString {
+    env::var_os(key).unwrap_or_else(|| {
+        eprintln!("Environment variable ${key} is not set during execution of build script");
+        process::exit(1);
+    })
+}
diff --git a/subprojects/thiserror/build/probe.rs b/subprojects/thiserror/build/probe.rs
new file mode 100644
index 0000000..ee126d4
--- /dev/null
+++ b/subprojects/thiserror/build/probe.rs
@@ -0,0 +1,33 @@
+// This code exercises the surface area that we expect of the Error generic
+// member access API. If the current toolchain is able to compile it, then
+// thiserror is able to provide backtrace support.
+
+#![no_std]
+#![feature(error_generic_member_access)]
+
+use core::error::{Error, Request};
+use core::fmt::{self, Debug, Display};
+
+struct MyError(Thing);
+struct Thing;
+
+impl Debug for MyError {
+    fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+        unimplemented!()
+    }
+}
+
+impl Display for MyError {
+    fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+        unimplemented!()
+    }
+}
+
+impl Error for MyError {
+    fn provide<'a>(&'a self, request: &mut Request<'a>) {
+        request.provide_ref(&self.0);
+    }
+}
+
+// Include in sccache cache key.
+const _: Option<&str> = option_env!("RUSTC_BOOTSTRAP");
diff --git a/subprojects/thiserror/impl/Cargo.toml b/subprojects/thiserror/impl/Cargo.toml
new file mode 100644
index 0000000..1d7d2f9
--- /dev/null
+++ b/subprojects/thiserror/impl/Cargo.toml
@@ -0,0 +1,28 @@
+[package]
+name = "thiserror-impl"
+version = "2.0.17"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+description = "Implementation detail of the `thiserror` crate"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/dtolnay/thiserror"
+rust-version = "1.68"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0.74"
+quote = "1.0.35"
+syn = "2.0.87"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+rustdoc-args = [
+    "--generate-link-to-definition",
+    "--generate-macro-expansion",
+    "--extern-html-root-url=core=https://doc.rust-lang.org",
+    "--extern-html-root-url=alloc=https://doc.rust-lang.org",
+    "--extern-html-root-url=std=https://doc.rust-lang.org",
+    "--extern-html-root-url=proc_macro=https://doc.rust-lang.org",
+]
diff --git a/subprojects/thiserror/impl/LICENSE-APACHE b/subprojects/thiserror/impl/LICENSE-APACHE
new file mode 120000
index 0000000..965b606
--- /dev/null
+++ b/subprojects/thiserror/impl/LICENSE-APACHE
@@ -0,0 +1 @@
+../LICENSE-APACHE
\ No newline at end of file
diff --git a/subprojects/thiserror/impl/LICENSE-MIT b/subprojects/thiserror/impl/LICENSE-MIT
new file mode 120000
index 0000000..76219eb
--- /dev/null
+++ b/subprojects/thiserror/impl/LICENSE-MIT
@@ -0,0 +1 @@
+../LICENSE-MIT
\ No newline at end of file
diff --git a/subprojects/thiserror/impl/src/ast.rs b/subprojects/thiserror/impl/src/ast.rs
new file mode 100644
index 0000000..77f9583
--- /dev/null
+++ b/subprojects/thiserror/impl/src/ast.rs
@@ -0,0 +1,185 @@
+use crate::attr::{self, Attrs};
+use crate::generics::ParamsInScope;
+use crate::unraw::{IdentUnraw, MemberUnraw};
+use proc_macro2::Span;
+use std::fmt::{self, Display};
+use syn::{
+    Data, DataEnum, DataStruct, DeriveInput, Error, Fields, Generics, Ident, Index, Result, Type,
+};
+
+pub enum Input<'a> {
+    Struct(Struct<'a>),
+    Enum(Enum<'a>),
+}
+
+pub struct Struct<'a> {
+    pub attrs: Attrs<'a>,
+    pub ident: Ident,
+    pub generics: &'a Generics,
+    pub fields: Vec<Field<'a>>,
+}
+
+pub struct Enum<'a> {
+    pub attrs: Attrs<'a>,
+    pub ident: Ident,
+    pub generics: &'a Generics,
+    pub variants: Vec<Variant<'a>>,
+}
+
+pub struct Variant<'a> {
+    pub original: &'a syn::Variant,
+    pub attrs: Attrs<'a>,
+    pub ident: Ident,
+    pub fields: Vec<Field<'a>>,
+}
+
+pub struct Field<'a> {
+    pub original: &'a syn::Field,
+    pub attrs: Attrs<'a>,
+    pub member: MemberUnraw,
+    pub ty: &'a Type,
+    pub contains_generic: bool,
+}
+
+#[derive(Copy, Clone)]
+pub enum ContainerKind {
+    Struct,
+    TupleStruct,
+    UnitStruct,
+    StructVariant,
+    TupleVariant,
+    UnitVariant,
+}
+
+impl<'a> Input<'a> {
+    pub fn from_syn(node: &'a DeriveInput) -> Result<Self> {
+        match &node.data {
+            Data::Struct(data) => Struct::from_syn(node, data).map(Input::Struct),
+            Data::Enum(data) => Enum::from_syn(node, data).map(Input::Enum),
+            Data::Union(_) => Err(Error::new_spanned(
+                node,
+                "union as errors are not supported",
+            )),
+        }
+    }
+}
+
+impl<'a> Struct<'a> {
+    fn from_syn(node: &'a DeriveInput, data: &'a DataStruct) -> Result<Self> {
+        let mut attrs = attr::get(&node.attrs)?;
+        let scope = ParamsInScope::new(&node.generics);
+        let fields = Field::multiple_from_syn(&data.fields, &scope)?;
+        if let Some(display) = &mut attrs.display {
+            let container = ContainerKind::from_struct(data);
+            display.expand_shorthand(&fields, container)?;
+        }
+        Ok(Struct {
+            attrs,
+            ident: node.ident.clone(),
+            generics: &node.generics,
+            fields,
+        })
+    }
+}
+
+impl<'a> Enum<'a> {
+    fn from_syn(node: &'a DeriveInput, data: &'a DataEnum) -> Result<Self> {
+        let attrs = attr::get(&node.attrs)?;
+        let scope = ParamsInScope::new(&node.generics);
+        let variants = data
+            .variants
+            .iter()
+            .map(|node| {
+                let mut variant = Variant::from_syn(node, &scope)?;
+                if variant.attrs.display.is_none()
+                    && variant.attrs.transparent.is_none()
+                    && variant.attrs.fmt.is_none()
+                {
+                    variant.attrs.display.clone_from(&attrs.display);
+                    variant.attrs.transparent = attrs.transparent;
+                    variant.attrs.fmt.clone_from(&attrs.fmt);
+                }
+                if let Some(display) = &mut variant.attrs.display {
+                    let container = ContainerKind::from_variant(node);
+                    display.expand_shorthand(&variant.fields, container)?;
+                }
+                Ok(variant)
+            })
+            .collect::<Result<_>>()?;
+        Ok(Enum {
+            attrs,
+            ident: node.ident.clone(),
+            generics: &node.generics,
+            variants,
+        })
+    }
+}
+
+impl<'a> Variant<'a> {
+    fn from_syn(node: &'a syn::Variant, scope: &ParamsInScope<'a>) -> Result<Self> {
+        let attrs = attr::get(&node.attrs)?;
+        Ok(Variant {
+            original: node,
+            attrs,
+            ident: node.ident.clone(),
+            fields: Field::multiple_from_syn(&node.fields, scope)?,
+        })
+    }
+}
+
+impl<'a> Field<'a> {
+    fn multiple_from_syn(fields: &'a Fields, scope: &ParamsInScope<'a>) -> Result<Vec<Self>> {
+        fields
+            .iter()
+            .enumerate()
+            .map(|(i, field)| Field::from_syn(i, field, scope))
+            .collect()
+    }
+
+    fn from_syn(i: usize, node: &'a syn::Field, scope: &ParamsInScope<'a>) -> Result<Self> {
+        Ok(Field {
+            original: node,
+            attrs: attr::get(&node.attrs)?,
+            member: match &node.ident {
+                Some(name) => MemberUnraw::Named(IdentUnraw::new(name.clone())),
+                None => MemberUnraw::Unnamed(Index {
+                    index: i as u32,
+                    span: Span::call_site(),
+                }),
+            },
+            ty: &node.ty,
+            contains_generic: scope.intersects(&node.ty),
+        })
+    }
+}
+
+impl ContainerKind {
+    fn from_struct(node: &DataStruct) -> Self {
+        match node.fields {
+            Fields::Named(_) => ContainerKind::Struct,
+            Fields::Unnamed(_) => ContainerKind::TupleStruct,
+            Fields::Unit => ContainerKind::UnitStruct,
+        }
+    }
+
+    fn from_variant(node: &syn::Variant) -> Self {
+        match node.fields {
+            Fields::Named(_) => ContainerKind::StructVariant,
+            Fields::Unnamed(_) => ContainerKind::TupleVariant,
+            Fields::Unit => ContainerKind::UnitVariant,
+        }
+    }
+}
+
+impl Display for ContainerKind {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(match self {
+            ContainerKind::Struct => "struct",
+            ContainerKind::TupleStruct => "tuple struct",
+            ContainerKind::UnitStruct => "unit struct",
+            ContainerKind::StructVariant => "struct variant",
+            ContainerKind::TupleVariant => "tuple variant",
+            ContainerKind::UnitVariant => "unit variant",
+        })
+    }
+}
diff --git a/subprojects/thiserror/impl/src/attr.rs b/subprojects/thiserror/impl/src/attr.rs
new file mode 100644
index 0000000..7ad83e0
--- /dev/null
+++ b/subprojects/thiserror/impl/src/attr.rs
@@ -0,0 +1,358 @@
+use proc_macro2::{Delimiter, Group, Literal, Punct, Spacing, Span, TokenStream, TokenTree};
+use quote::{format_ident, quote, quote_spanned, ToTokens};
+use std::collections::BTreeSet as Set;
+use syn::parse::discouraged::Speculative;
+use syn::parse::{End, ParseStream};
+use syn::{
+    braced, bracketed, parenthesized, token, Attribute, Error, ExprPath, Ident, Index, LitFloat,
+    LitInt, LitStr, Meta, Result, Token,
+};
+
+pub struct Attrs<'a> {
+    pub display: Option<Display<'a>>,
+    pub source: Option<Source<'a>>,
+    pub backtrace: Option<&'a Attribute>,
+    pub from: Option<From<'a>>,
+    pub transparent: Option<Transparent<'a>>,
+    pub fmt: Option<Fmt<'a>>,
+}
+
+#[derive(Clone)]
+pub struct Display<'a> {
+    pub original: &'a Attribute,
+    pub fmt: LitStr,
+    pub args: TokenStream,
+    pub requires_fmt_machinery: bool,
+    pub has_bonus_display: bool,
+    pub infinite_recursive: bool,
+    pub implied_bounds: Set<(usize, Trait)>,
+    pub bindings: Vec<(Ident, TokenStream)>,
+}
+
+#[derive(Copy, Clone)]
+pub struct Source<'a> {
+    pub original: &'a Attribute,
+    pub span: Span,
+}
+
+#[derive(Copy, Clone)]
+pub struct From<'a> {
+    pub original: &'a Attribute,
+    pub span: Span,
+}
+
+#[derive(Copy, Clone)]
+pub struct Transparent<'a> {
+    pub original: &'a Attribute,
+    pub span: Span,
+}
+
+#[derive(Clone)]
+pub struct Fmt<'a> {
+    pub original: &'a Attribute,
+    pub path: ExprPath,
+}
+
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug)]
+pub enum Trait {
+    Debug,
+    Display,
+    Octal,
+    LowerHex,
+    UpperHex,
+    Pointer,
+    Binary,
+    LowerExp,
+    UpperExp,
+}
+
+pub fn get(input: &[Attribute]) -> Result<Attrs> {
+    let mut attrs = Attrs {
+        display: None,
+        source: None,
+        backtrace: None,
+        from: None,
+        transparent: None,
+        fmt: None,
+    };
+
+    for attr in input {
+        if attr.path().is_ident("error") {
+            parse_error_attribute(&mut attrs, attr)?;
+        } else if attr.path().is_ident("source") {
+            attr.meta.require_path_only()?;
+            if attrs.source.is_some() {
+                return Err(Error::new_spanned(attr, "duplicate #[source] attribute"));
+            }
+            let span = (attr.pound_token.span)
+                .join(attr.bracket_token.span.join())
+                .unwrap_or(attr.path().get_ident().unwrap().span());
+            attrs.source = Some(Source {
+                original: attr,
+                span,
+            });
+        } else if attr.path().is_ident("backtrace") {
+            attr.meta.require_path_only()?;
+            if attrs.backtrace.is_some() {
+                return Err(Error::new_spanned(attr, "duplicate #[backtrace] attribute"));
+            }
+            attrs.backtrace = Some(attr);
+        } else if attr.path().is_ident("from") {
+            match attr.meta {
+                Meta::Path(_) => {}
+                Meta::List(_) | Meta::NameValue(_) => {
+                    // Assume this is meant for derive_more crate or something.
+                    continue;
+                }
+            }
+            if attrs.from.is_some() {
+                return Err(Error::new_spanned(attr, "duplicate #[from] attribute"));
+            }
+            let span = (attr.pound_token.span)
+                .join(attr.bracket_token.span.join())
+                .unwrap_or(attr.path().get_ident().unwrap().span());
+            attrs.from = Some(From {
+                original: attr,
+                span,
+            });
+        }
+    }
+
+    Ok(attrs)
+}
+
+fn parse_error_attribute<'a>(attrs: &mut Attrs<'a>, attr: &'a Attribute) -> Result<()> {
+    mod kw {
+        syn::custom_keyword!(transparent);
+        syn::custom_keyword!(fmt);
+    }
+
+    attr.parse_args_with(|input: ParseStream| {
+        let lookahead = input.lookahead1();
+        let fmt = if lookahead.peek(LitStr) {
+            input.parse::<LitStr>()?
+        } else if lookahead.peek(kw::transparent) {
+            let kw: kw::transparent = input.parse()?;
+            if attrs.transparent.is_some() {
+                return Err(Error::new_spanned(
+                    attr,
+                    "duplicate #[error(transparent)] attribute",
+                ));
+            }
+            attrs.transparent = Some(Transparent {
+                original: attr,
+                span: kw.span,
+            });
+            return Ok(());
+        } else if lookahead.peek(kw::fmt) {
+            input.parse::<kw::fmt>()?;
+            input.parse::<Token![=]>()?;
+            let path: ExprPath = input.parse()?;
+            if attrs.fmt.is_some() {
+                return Err(Error::new_spanned(
+                    attr,
+                    "duplicate #[error(fmt = ...)] attribute",
+                ));
+            }
+            attrs.fmt = Some(Fmt {
+                original: attr,
+                path,
+            });
+            return Ok(());
+        } else {
+            return Err(lookahead.error());
+        };
+
+        let args = if input.is_empty() || input.peek(Token![,]) && input.peek2(End) {
+            input.parse::<Option<Token![,]>>()?;
+            TokenStream::new()
+        } else {
+            parse_token_expr(input, false)?
+        };
+
+        let requires_fmt_machinery = !args.is_empty();
+
+        let display = Display {
+            original: attr,
+            fmt,
+            args,
+            requires_fmt_machinery,
+            has_bonus_display: false,
+            infinite_recursive: false,
+            implied_bounds: Set::new(),
+            bindings: Vec::new(),
+        };
+        if attrs.display.is_some() {
+            return Err(Error::new_spanned(
+                attr,
+                "only one #[error(...)] attribute is allowed",
+            ));
+        }
+        attrs.display = Some(display);
+        Ok(())
+    })
+}
+
+fn parse_token_expr(input: ParseStream, mut begin_expr: bool) -> Result<TokenStream> {
+    let mut tokens = Vec::new();
+    while !input.is_empty() {
+        if input.peek(token::Group) {
+            let group: TokenTree = input.parse()?;
+            tokens.push(group);
+            begin_expr = false;
+            continue;
+        }
+
+        if begin_expr && input.peek(Token![.]) {
+            if input.peek2(Ident) {
+                input.parse::<Token![.]>()?;
+                begin_expr = false;
+                continue;
+            } else if input.peek2(LitInt) {
+                input.parse::<Token![.]>()?;
+                let int: Index = input.parse()?;
+                tokens.push({
+                    let ident = format_ident!("_{}", int.index, span = int.span);
+                    TokenTree::Ident(ident)
+                });
+                begin_expr = false;
+                continue;
+            } else if input.peek2(LitFloat) {
+                let ahead = input.fork();
+                ahead.parse::<Token![.]>()?;
+                let float: LitFloat = ahead.parse()?;
+                let repr = float.to_string();
+                let mut indices = repr.split('.').map(syn::parse_str::<Index>);
+                if let (Some(Ok(first)), Some(Ok(second)), None) =
+                    (indices.next(), indices.next(), indices.next())
+                {
+                    input.advance_to(&ahead);
+                    tokens.push({
+                        let ident = format_ident!("_{}", first, span = float.span());
+                        TokenTree::Ident(ident)
+                    });
+                    tokens.push({
+                        let mut punct = Punct::new('.', Spacing::Alone);
+                        punct.set_span(float.span());
+                        TokenTree::Punct(punct)
+                    });
+                    tokens.push({
+                        let mut literal = Literal::u32_unsuffixed(second.index);
+                        literal.set_span(float.span());
+                        TokenTree::Literal(literal)
+                    });
+                    begin_expr = false;
+                    continue;
+                }
+            }
+        }
+
+        begin_expr = input.peek(Token![break])
+            || input.peek(Token![continue])
+            || input.peek(Token![if])
+            || input.peek(Token![in])
+            || input.peek(Token![match])
+            || input.peek(Token![mut])
+            || input.peek(Token![return])
+            || input.peek(Token![while])
+            || input.peek(Token![+])
+            || input.peek(Token![&])
+            || input.peek(Token![!])
+            || input.peek(Token![^])
+            || input.peek(Token![,])
+            || input.peek(Token![/])
+            || input.peek(Token![=])
+            || input.peek(Token![>])
+            || input.peek(Token![<])
+            || input.peek(Token![|])
+            || input.peek(Token![%])
+            || input.peek(Token![;])
+            || input.peek(Token![*])
+            || input.peek(Token![-]);
+
+        let token: TokenTree = if input.peek(token::Paren) {
+            let content;
+            let delimiter = parenthesized!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Parenthesis, nested);
+            group.set_span(delimiter.span.join());
+            TokenTree::Group(group)
+        } else if input.peek(token::Brace) {
+            let content;
+            let delimiter = braced!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Brace, nested);
+            group.set_span(delimiter.span.join());
+            TokenTree::Group(group)
+        } else if input.peek(token::Bracket) {
+            let content;
+            let delimiter = bracketed!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Bracket, nested);
+            group.set_span(delimiter.span.join());
+            TokenTree::Group(group)
+        } else {
+            input.parse()?
+        };
+        tokens.push(token);
+    }
+    Ok(TokenStream::from_iter(tokens))
+}
+
+impl ToTokens for Display<'_> {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        if self.infinite_recursive {
+            let span = self.fmt.span();
+            tokens.extend(quote_spanned! {span=>
+                #[warn(unconditional_recursion)]
+                fn _fmt() { _fmt() }
+            });
+        }
+
+        let fmt = &self.fmt;
+        let args = &self.args;
+
+        // Currently `write!(f, "text")` produces less efficient code than
+        // `f.write_str("text")`. We recognize the case when the format string
+        // has no braces and no interpolated values, and generate simpler code.
+        let write = if self.requires_fmt_machinery {
+            quote! {
+                ::core::write!(__formatter, #fmt #args)
+            }
+        } else {
+            quote! {
+                __formatter.write_str(#fmt)
+            }
+        };
+
+        tokens.extend(if self.bindings.is_empty() {
+            write
+        } else {
+            let locals = self.bindings.iter().map(|(local, _value)| local);
+            let values = self.bindings.iter().map(|(_local, value)| value);
+            quote! {
+                match (#(#values,)*) {
+                    (#(#locals,)*) => #write
+                }
+            }
+        });
+    }
+}
+
+impl ToTokens for Trait {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let trait_name = match self {
+            Trait::Debug => "Debug",
+            Trait::Display => "Display",
+            Trait::Octal => "Octal",
+            Trait::LowerHex => "LowerHex",
+            Trait::UpperHex => "UpperHex",
+            Trait::Pointer => "Pointer",
+            Trait::Binary => "Binary",
+            Trait::LowerExp => "LowerExp",
+            Trait::UpperExp => "UpperExp",
+        };
+        let ident = Ident::new(trait_name, Span::call_site());
+        tokens.extend(quote!(::core::fmt::#ident));
+    }
+}
diff --git a/subprojects/thiserror/impl/src/expand.rs b/subprojects/thiserror/impl/src/expand.rs
new file mode 100644
index 0000000..97466dd
--- /dev/null
+++ b/subprojects/thiserror/impl/src/expand.rs
@@ -0,0 +1,584 @@
+use crate::ast::{Enum, Field, Input, Struct};
+use crate::attr::Trait;
+use crate::fallback;
+use crate::generics::InferredBounds;
+use crate::private;
+use crate::unraw::MemberUnraw;
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::{format_ident, quote, quote_spanned, ToTokens};
+use std::collections::BTreeSet as Set;
+use syn::{DeriveInput, GenericArgument, PathArguments, Result, Token, Type};
+
+pub fn derive(input: &DeriveInput) -> TokenStream {
+    match try_expand(input) {
+        Ok(expanded) => expanded,
+        // If there are invalid attributes in the input, expand to an Error impl
+        // anyway to minimize spurious secondary errors in other code that uses
+        // this type as an Error.
+        Err(error) => fallback::expand(input, error),
+    }
+}
+
+fn try_expand(input: &DeriveInput) -> Result<TokenStream> {
+    let input = Input::from_syn(input)?;
+    input.validate()?;
+    Ok(match input {
+        Input::Struct(input) => impl_struct(input),
+        Input::Enum(input) => impl_enum(input),
+    })
+}
+
+fn impl_struct(input: Struct) -> TokenStream {
+    let ty = call_site_ident(&input.ident);
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let mut error_inferred_bounds = InferredBounds::new();
+
+    let source_body = if let Some(transparent_attr) = &input.attrs.transparent {
+        let only_field = &input.fields[0];
+        if only_field.contains_generic {
+            error_inferred_bounds.insert(only_field.ty, quote!(::thiserror::#private::Error));
+        }
+        let member = &only_field.member;
+        Some(quote_spanned! {transparent_attr.span=>
+            ::thiserror::#private::Error::source(self.#member.as_dyn_error())
+        })
+    } else if let Some(source_field) = input.source_field() {
+        let source = &source_field.member;
+        if source_field.contains_generic {
+            let ty = unoptional_type(source_field.ty);
+            error_inferred_bounds.insert(ty, quote!(::thiserror::#private::Error + 'static));
+        }
+        let asref = if type_is_option(source_field.ty) {
+            Some(quote_spanned!(source.span()=> .as_ref()?))
+        } else {
+            None
+        };
+        let dyn_error = quote_spanned! {source_field.source_span()=>
+            self.#source #asref.as_dyn_error()
+        };
+        Some(quote! {
+            ::core::option::Option::Some(#dyn_error)
+        })
+    } else {
+        None
+    };
+    let source_method = source_body.map(|body| {
+        quote! {
+            fn source(&self) -> ::core::option::Option<&(dyn ::thiserror::#private::Error + 'static)> {
+                use ::thiserror::#private::AsDynError as _;
+                #body
+            }
+        }
+    });
+
+    let provide_method = input.backtrace_field().map(|backtrace_field| {
+        let request = quote!(request);
+        let backtrace = &backtrace_field.member;
+        let body = if let Some(source_field) = input.source_field() {
+            let source = &source_field.member;
+            let source_provide = if type_is_option(source_field.ty) {
+                quote_spanned! {source.span()=>
+                    if let ::core::option::Option::Some(source) = &self.#source {
+                        source.thiserror_provide(#request);
+                    }
+                }
+            } else {
+                quote_spanned! {source.span()=>
+                    self.#source.thiserror_provide(#request);
+                }
+            };
+            let self_provide = if source == backtrace {
+                None
+            } else if type_is_option(backtrace_field.ty) {
+                Some(quote! {
+                    if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
+                        #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                    }
+                })
+            } else {
+                Some(quote! {
+                    #request.provide_ref::<::thiserror::#private::Backtrace>(&self.#backtrace);
+                })
+            };
+            quote! {
+                use ::thiserror::#private::ThiserrorProvide as _;
+                #source_provide
+                #self_provide
+            }
+        } else if type_is_option(backtrace_field.ty) {
+            quote! {
+                if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
+                    #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                }
+            }
+        } else {
+            quote! {
+                #request.provide_ref::<::thiserror::#private::Backtrace>(&self.#backtrace);
+            }
+        };
+        quote! {
+            fn provide<'_request>(&'_request self, #request: &mut ::core::error::Request<'_request>) {
+                #body
+            }
+        }
+    });
+
+    let mut display_implied_bounds = Set::new();
+    let display_body = if input.attrs.transparent.is_some() {
+        let only_field = &input.fields[0].member;
+        display_implied_bounds.insert((0, Trait::Display));
+        Some(quote! {
+            ::core::fmt::Display::fmt(&self.#only_field, __formatter)
+        })
+    } else if let Some(display) = &input.attrs.display {
+        display_implied_bounds.clone_from(&display.implied_bounds);
+        let use_as_display = use_as_display(display.has_bonus_display);
+        let pat = fields_pat(&input.fields);
+        Some(quote! {
+            #use_as_display
+            #[allow(unused_variables, deprecated)]
+            let Self #pat = self;
+            #display
+        })
+    } else {
+        None
+    };
+    let display_impl = display_body.map(|body| {
+        let mut display_inferred_bounds = InferredBounds::new();
+        for (field, bound) in display_implied_bounds {
+            let field = &input.fields[field];
+            if field.contains_generic {
+                display_inferred_bounds.insert(field.ty, bound);
+            }
+        }
+        let display_where_clause = display_inferred_bounds.augment_where_clause(input.generics);
+        quote! {
+            #[allow(unused_qualifications)]
+            #[automatically_derived]
+            impl #impl_generics ::core::fmt::Display for #ty #ty_generics #display_where_clause {
+                #[allow(clippy::used_underscore_binding)]
+                fn fmt(&self, __formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                    #body
+                }
+            }
+        }
+    });
+
+    let from_impl = input.from_field().map(|from_field| {
+        let span = from_field.attrs.from.unwrap().span;
+        let backtrace_field = input.distinct_backtrace_field();
+        let from = unoptional_type(from_field.ty);
+        let source_var = Ident::new("source", span);
+        let body = from_initializer(from_field, backtrace_field, &source_var);
+        let from_function = quote! {
+            fn from(#source_var: #from) -> Self {
+                #ty #body
+            }
+        };
+        let from_impl = quote_spanned! {span=>
+            #[automatically_derived]
+            impl #impl_generics ::core::convert::From<#from> for #ty #ty_generics #where_clause {
+                #from_function
+            }
+        };
+        Some(quote! {
+            #[allow(
+                deprecated,
+                unused_qualifications,
+                clippy::elidable_lifetime_names,
+                clippy::needless_lifetimes,
+            )]
+            #from_impl
+        })
+    });
+
+    if input.generics.type_params().next().is_some() {
+        let self_token = <Token![Self]>::default();
+        error_inferred_bounds.insert(self_token, Trait::Debug);
+        error_inferred_bounds.insert(self_token, Trait::Display);
+    }
+    let error_where_clause = error_inferred_bounds.augment_where_clause(input.generics);
+
+    quote! {
+        #[allow(unused_qualifications)]
+        #[automatically_derived]
+        impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #error_where_clause {
+            #source_method
+            #provide_method
+        }
+        #display_impl
+        #from_impl
+    }
+}
+
+fn impl_enum(input: Enum) -> TokenStream {
+    let ty = call_site_ident(&input.ident);
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let mut error_inferred_bounds = InferredBounds::new();
+
+    let source_method = if input.has_source() {
+        let arms = input.variants.iter().map(|variant| {
+            let ident = &variant.ident;
+            if let Some(transparent_attr) = &variant.attrs.transparent {
+                let only_field = &variant.fields[0];
+                if only_field.contains_generic {
+                    error_inferred_bounds.insert(only_field.ty, quote!(::thiserror::#private::Error));
+                }
+                let member = &only_field.member;
+                let source = quote_spanned! {transparent_attr.span=>
+                    ::thiserror::#private::Error::source(transparent.as_dyn_error())
+                };
+                quote! {
+                    #ty::#ident {#member: transparent} => #source,
+                }
+            } else if let Some(source_field) = variant.source_field() {
+                let source = &source_field.member;
+                if source_field.contains_generic {
+                    let ty = unoptional_type(source_field.ty);
+                    error_inferred_bounds.insert(ty, quote!(::thiserror::#private::Error + 'static));
+                }
+                let asref = if type_is_option(source_field.ty) {
+                    Some(quote_spanned!(source.span()=> .as_ref()?))
+                } else {
+                    None
+                };
+                let varsource = quote!(source);
+                let dyn_error = quote_spanned! {source_field.source_span()=>
+                    #varsource #asref.as_dyn_error()
+                };
+                quote! {
+                    #ty::#ident {#source: #varsource, ..} => ::core::option::Option::Some(#dyn_error),
+                }
+            } else {
+                quote! {
+                    #ty::#ident {..} => ::core::option::Option::None,
+                }
+            }
+        });
+        Some(quote! {
+            fn source(&self) -> ::core::option::Option<&(dyn ::thiserror::#private::Error + 'static)> {
+                use ::thiserror::#private::AsDynError as _;
+                #[allow(deprecated)]
+                match self {
+                    #(#arms)*
+                }
+            }
+        })
+    } else {
+        None
+    };
+
+    let provide_method = if input.has_backtrace() {
+        let request = quote!(request);
+        let arms = input.variants.iter().map(|variant| {
+            let ident = &variant.ident;
+            match (variant.backtrace_field(), variant.source_field()) {
+                (Some(backtrace_field), Some(source_field))
+                    if backtrace_field.attrs.backtrace.is_none() =>
+                {
+                    let backtrace = &backtrace_field.member;
+                    let source = &source_field.member;
+                    let varsource = quote!(source);
+                    let source_provide = if type_is_option(source_field.ty) {
+                        quote_spanned! {source.span()=>
+                            if let ::core::option::Option::Some(source) = #varsource {
+                                source.thiserror_provide(#request);
+                            }
+                        }
+                    } else {
+                        quote_spanned! {source.span()=>
+                            #varsource.thiserror_provide(#request);
+                        }
+                    };
+                    let self_provide = if type_is_option(backtrace_field.ty) {
+                        quote! {
+                            if let ::core::option::Option::Some(backtrace) = backtrace {
+                                #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                            }
+                        }
+                    } else {
+                        quote! {
+                            #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                        }
+                    };
+                    quote! {
+                        #ty::#ident {
+                            #backtrace: backtrace,
+                            #source: #varsource,
+                            ..
+                        } => {
+                            use ::thiserror::#private::ThiserrorProvide as _;
+                            #source_provide
+                            #self_provide
+                        }
+                    }
+                }
+                (Some(backtrace_field), Some(source_field))
+                    if backtrace_field.member == source_field.member =>
+                {
+                    let backtrace = &backtrace_field.member;
+                    let varsource = quote!(source);
+                    let source_provide = if type_is_option(source_field.ty) {
+                        quote_spanned! {backtrace.span()=>
+                            if let ::core::option::Option::Some(source) = #varsource {
+                                source.thiserror_provide(#request);
+                            }
+                        }
+                    } else {
+                        quote_spanned! {backtrace.span()=>
+                            #varsource.thiserror_provide(#request);
+                        }
+                    };
+                    quote! {
+                        #ty::#ident {#backtrace: #varsource, ..} => {
+                            use ::thiserror::#private::ThiserrorProvide as _;
+                            #source_provide
+                        }
+                    }
+                }
+                (Some(backtrace_field), _) => {
+                    let backtrace = &backtrace_field.member;
+                    let body = if type_is_option(backtrace_field.ty) {
+                        quote! {
+                            if let ::core::option::Option::Some(backtrace) = backtrace {
+                                #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                            }
+                        }
+                    } else {
+                        quote! {
+                            #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                        }
+                    };
+                    quote! {
+                        #ty::#ident {#backtrace: backtrace, ..} => {
+                            #body
+                        }
+                    }
+                }
+                (None, _) => quote! {
+                    #ty::#ident {..} => {}
+                },
+            }
+        });
+        Some(quote! {
+            fn provide<'_request>(&'_request self, #request: &mut ::core::error::Request<'_request>) {
+                #[allow(deprecated)]
+                match self {
+                    #(#arms)*
+                }
+            }
+        })
+    } else {
+        None
+    };
+
+    let display_impl = if input.has_display() {
+        let mut display_inferred_bounds = InferredBounds::new();
+        let has_bonus_display = input.variants.iter().any(|v| {
+            v.attrs
+                .display
+                .as_ref()
+                .map_or(false, |display| display.has_bonus_display)
+        });
+        let use_as_display = use_as_display(has_bonus_display);
+        let void_deref = if input.variants.is_empty() {
+            Some(quote!(*))
+        } else {
+            None
+        };
+        let arms = input.variants.iter().map(|variant| {
+            let mut display_implied_bounds = Set::new();
+            let display = if let Some(display) = &variant.attrs.display {
+                display_implied_bounds.clone_from(&display.implied_bounds);
+                display.to_token_stream()
+            } else if let Some(fmt) = &variant.attrs.fmt {
+                let fmt_path = &fmt.path;
+                let vars = variant.fields.iter().map(|field| match &field.member {
+                    MemberUnraw::Named(ident) => ident.to_local(),
+                    MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
+                });
+                quote!(#fmt_path(#(#vars,)* __formatter))
+            } else {
+                let only_field = match &variant.fields[0].member {
+                    MemberUnraw::Named(ident) => ident.to_local(),
+                    MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
+                };
+                display_implied_bounds.insert((0, Trait::Display));
+                quote!(::core::fmt::Display::fmt(#only_field, __formatter))
+            };
+            for (field, bound) in display_implied_bounds {
+                let field = &variant.fields[field];
+                if field.contains_generic {
+                    display_inferred_bounds.insert(field.ty, bound);
+                }
+            }
+            let ident = &variant.ident;
+            let pat = fields_pat(&variant.fields);
+            quote! {
+                #ty::#ident #pat => #display
+            }
+        });
+        let arms = arms.collect::<Vec<_>>();
+        let display_where_clause = display_inferred_bounds.augment_where_clause(input.generics);
+        Some(quote! {
+            #[allow(unused_qualifications)]
+            #[automatically_derived]
+            impl #impl_generics ::core::fmt::Display for #ty #ty_generics #display_where_clause {
+                fn fmt(&self, __formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                    #use_as_display
+                    #[allow(unused_variables, deprecated, clippy::used_underscore_binding)]
+                    match #void_deref self {
+                        #(#arms,)*
+                    }
+                }
+            }
+        })
+    } else {
+        None
+    };
+
+    let from_impls = input.variants.iter().filter_map(|variant| {
+        let from_field = variant.from_field()?;
+        let span = from_field.attrs.from.unwrap().span;
+        let backtrace_field = variant.distinct_backtrace_field();
+        let variant = &variant.ident;
+        let from = unoptional_type(from_field.ty);
+        let source_var = Ident::new("source", span);
+        let body = from_initializer(from_field, backtrace_field, &source_var);
+        let from_function = quote! {
+            fn from(#source_var: #from) -> Self {
+                #ty::#variant #body
+            }
+        };
+        let from_impl = quote_spanned! {span=>
+            #[automatically_derived]
+            impl #impl_generics ::core::convert::From<#from> for #ty #ty_generics #where_clause {
+                #from_function
+            }
+        };
+        Some(quote! {
+            #[allow(
+                deprecated,
+                unused_qualifications,
+                clippy::elidable_lifetime_names,
+                clippy::needless_lifetimes,
+            )]
+            #from_impl
+        })
+    });
+
+    if input.generics.type_params().next().is_some() {
+        let self_token = <Token![Self]>::default();
+        error_inferred_bounds.insert(self_token, Trait::Debug);
+        error_inferred_bounds.insert(self_token, Trait::Display);
+    }
+    let error_where_clause = error_inferred_bounds.augment_where_clause(input.generics);
+
+    quote! {
+        #[allow(unused_qualifications)]
+        #[automatically_derived]
+        impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #error_where_clause {
+            #source_method
+            #provide_method
+        }
+        #display_impl
+        #(#from_impls)*
+    }
+}
+
+// Create an ident with which we can expand `impl Trait for #ident {}` on a
+// deprecated type without triggering deprecation warning on the generated impl.
+pub(crate) fn call_site_ident(ident: &Ident) -> Ident {
+    let mut ident = ident.clone();
+    ident.set_span(ident.span().resolved_at(Span::call_site()));
+    ident
+}
+
+fn fields_pat(fields: &[Field]) -> TokenStream {
+    let mut members = fields.iter().map(|field| &field.member).peekable();
+    match members.peek() {
+        Some(MemberUnraw::Named(_)) => quote!({ #(#members),* }),
+        Some(MemberUnraw::Unnamed(_)) => {
+            let vars = members.map(|member| match member {
+                MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
+                MemberUnraw::Named(_) => unreachable!(),
+            });
+            quote!((#(#vars),*))
+        }
+        None => quote!({}),
+    }
+}
+
+fn use_as_display(needs_as_display: bool) -> Option<TokenStream> {
+    if needs_as_display {
+        Some(quote! {
+            use ::thiserror::#private::AsDisplay as _;
+        })
+    } else {
+        None
+    }
+}
+
+fn from_initializer(
+    from_field: &Field,
+    backtrace_field: Option<&Field>,
+    source_var: &Ident,
+) -> TokenStream {
+    let from_member = &from_field.member;
+    let some_source = if type_is_option(from_field.ty) {
+        quote!(::core::option::Option::Some(#source_var))
+    } else {
+        quote!(#source_var)
+    };
+    let backtrace = backtrace_field.map(|backtrace_field| {
+        let backtrace_member = &backtrace_field.member;
+        if type_is_option(backtrace_field.ty) {
+            quote! {
+                #backtrace_member: ::core::option::Option::Some(::thiserror::#private::Backtrace::capture()),
+            }
+        } else {
+            quote! {
+                #backtrace_member: ::core::convert::From::from(::thiserror::#private::Backtrace::capture()),
+            }
+        }
+    });
+    quote!({
+        #from_member: #some_source,
+        #backtrace
+    })
+}
+
+fn type_is_option(ty: &Type) -> bool {
+    type_parameter_of_option(ty).is_some()
+}
+
+fn unoptional_type(ty: &Type) -> TokenStream {
+    let unoptional = type_parameter_of_option(ty).unwrap_or(ty);
+    quote!(#unoptional)
+}
+
+fn type_parameter_of_option(ty: &Type) -> Option<&Type> {
+    let path = match ty {
+        Type::Path(ty) => &ty.path,
+        _ => return None,
+    };
+
+    let last = path.segments.last().unwrap();
+    if last.ident != "Option" {
+        return None;
+    }
+
+    let bracketed = match &last.arguments {
+        PathArguments::AngleBracketed(bracketed) => bracketed,
+        _ => return None,
+    };
+
+    if bracketed.args.len() != 1 {
+        return None;
+    }
+
+    match &bracketed.args[0] {
+        GenericArgument::Type(arg) => Some(arg),
+        _ => None,
+    }
+}
diff --git a/subprojects/thiserror/impl/src/fallback.rs b/subprojects/thiserror/impl/src/fallback.rs
new file mode 100644
index 0000000..9914aa5
--- /dev/null
+++ b/subprojects/thiserror/impl/src/fallback.rs
@@ -0,0 +1,33 @@
+use crate::expand::call_site_ident;
+use crate::private;
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::DeriveInput;
+
+pub(crate) fn expand(input: &DeriveInput, error: syn::Error) -> TokenStream {
+    let ty = call_site_ident(&input.ident);
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+
+    let error = error.to_compile_error();
+
+    quote! {
+        #error
+
+        #[allow(unused_qualifications)]
+        #[automatically_derived]
+        impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #where_clause
+        where
+            // Work around trivial bounds being unstable.
+            // https://github.com/rust-lang/rust/issues/48214
+            for<'workaround> #ty #ty_generics: ::core::fmt::Debug,
+        {}
+
+        #[allow(unused_qualifications)]
+        #[automatically_derived]
+        impl #impl_generics ::core::fmt::Display for #ty #ty_generics #where_clause {
+            fn fmt(&self, __formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                ::core::unreachable!()
+            }
+        }
+    }
+}
diff --git a/subprojects/thiserror/impl/src/fmt.rs b/subprojects/thiserror/impl/src/fmt.rs
new file mode 100644
index 0000000..2988ca3
--- /dev/null
+++ b/subprojects/thiserror/impl/src/fmt.rs
@@ -0,0 +1,323 @@
+use crate::ast::{ContainerKind, Field};
+use crate::attr::{Display, Trait};
+use crate::private;
+use crate::scan_expr::scan_expr;
+use crate::unraw::{IdentUnraw, MemberUnraw};
+use proc_macro2::{Delimiter, TokenStream, TokenTree};
+use quote::{format_ident, quote, quote_spanned, ToTokens as _};
+use std::collections::{BTreeSet, HashMap};
+use std::iter;
+use syn::ext::IdentExt;
+use syn::parse::discouraged::Speculative;
+use syn::parse::{Error, ParseStream, Parser, Result};
+use syn::{Expr, Ident, Index, LitStr, Token};
+
+impl Display<'_> {
+    pub fn expand_shorthand(&mut self, fields: &[Field], container: ContainerKind) -> Result<()> {
+        let raw_args = self.args.clone();
+        let FmtArguments {
+            named: user_named_args,
+            first_unnamed,
+        } = explicit_named_args.parse2(raw_args).unwrap();
+
+        let mut member_index = HashMap::new();
+        let mut extra_positional_arguments_allowed = true;
+        for (i, field) in fields.iter().enumerate() {
+            member_index.insert(&field.member, i);
+            extra_positional_arguments_allowed &= matches!(&field.member, MemberUnraw::Named(_));
+        }
+
+        let span = self.fmt.span();
+        let fmt = self.fmt.value();
+        let mut read = fmt.as_str();
+        let mut out = String::new();
+        let mut has_bonus_display = false;
+        let mut infinite_recursive = false;
+        let mut implied_bounds = BTreeSet::new();
+        let mut bindings = Vec::new();
+        let mut macro_named_args = BTreeSet::new();
+
+        self.requires_fmt_machinery = self.requires_fmt_machinery || fmt.contains('}');
+
+        while let Some(brace) = read.find('{') {
+            self.requires_fmt_machinery = true;
+            out += &read[..brace + 1];
+            read = &read[brace + 1..];
+            if read.starts_with('{') {
+                out.push('{');
+                read = &read[1..];
+                continue;
+            }
+            let next = match read.chars().next() {
+                Some(next) => next,
+                None => return Ok(()),
+            };
+            let member = match next {
+                '0'..='9' => {
+                    let int = take_int(&mut read);
+                    if !extra_positional_arguments_allowed {
+                        if let Some(first_unnamed) = &first_unnamed {
+                            let msg = format!("ambiguous reference to positional arguments by number in a {container}; change this to a named argument");
+                            return Err(Error::new_spanned(first_unnamed, msg));
+                        }
+                    }
+                    match int.parse::<u32>() {
+                        Ok(index) => MemberUnraw::Unnamed(Index { index, span }),
+                        Err(_) => return Ok(()),
+                    }
+                }
+                'a'..='z' | 'A'..='Z' | '_' => {
+                    if read.starts_with("r#") {
+                        continue;
+                    }
+                    let repr = take_ident(&mut read);
+                    if repr == "_" {
+                        // Invalid. Let rustc produce the diagnostic.
+                        out += repr;
+                        continue;
+                    }
+                    let ident = IdentUnraw::new(Ident::new(repr, span));
+                    if user_named_args.contains(&ident) {
+                        // Refers to a named argument written by the user, not to field.
+                        out += repr;
+                        continue;
+                    }
+                    MemberUnraw::Named(ident)
+                }
+                _ => continue,
+            };
+            let end_spec = match read.find('}') {
+                Some(end_spec) => end_spec,
+                None => return Ok(()),
+            };
+            let mut bonus_display = false;
+            let bound = match read[..end_spec].chars().next_back() {
+                Some('?') => Trait::Debug,
+                Some('o') => Trait::Octal,
+                Some('x') => Trait::LowerHex,
+                Some('X') => Trait::UpperHex,
+                Some('p') => Trait::Pointer,
+                Some('b') => Trait::Binary,
+                Some('e') => Trait::LowerExp,
+                Some('E') => Trait::UpperExp,
+                Some(_) => Trait::Display,
+                None => {
+                    bonus_display = true;
+                    has_bonus_display = true;
+                    Trait::Display
+                }
+            };
+            infinite_recursive |= member == *"self" && bound == Trait::Display;
+            let field = match member_index.get(&member) {
+                Some(&field) => field,
+                None => {
+                    out += &member.to_string();
+                    continue;
+                }
+            };
+            implied_bounds.insert((field, bound));
+            let formatvar_prefix = if bonus_display {
+                "__display"
+            } else if bound == Trait::Pointer {
+                "__pointer"
+            } else {
+                "__field"
+            };
+            let mut formatvar = IdentUnraw::new(match &member {
+                MemberUnraw::Unnamed(index) => format_ident!("{}{}", formatvar_prefix, index),
+                MemberUnraw::Named(ident) => {
+                    format_ident!("{}_{}", formatvar_prefix, ident.to_string())
+                }
+            });
+            while user_named_args.contains(&formatvar) {
+                formatvar = IdentUnraw::new(format_ident!("_{}", formatvar.to_string()));
+            }
+            formatvar.set_span(span);
+            out += &formatvar.to_string();
+            if !macro_named_args.insert(formatvar.clone()) {
+                // Already added to bindings by a previous use.
+                continue;
+            }
+            let mut binding_value = match &member {
+                MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
+                MemberUnraw::Named(ident) => ident.to_local(),
+            };
+            binding_value.set_span(span.resolved_at(fields[field].member.span()));
+            let wrapped_binding_value = if bonus_display {
+                quote_spanned!(span=> #binding_value.as_display())
+            } else if bound == Trait::Pointer {
+                quote!(::thiserror::#private::Var(#binding_value))
+            } else {
+                binding_value.into_token_stream()
+            };
+            bindings.push((formatvar.to_local(), wrapped_binding_value));
+        }
+
+        out += read;
+        self.fmt = LitStr::new(&out, self.fmt.span());
+        self.has_bonus_display = has_bonus_display;
+        self.infinite_recursive = infinite_recursive;
+        self.implied_bounds = implied_bounds;
+        self.bindings = bindings;
+        Ok(())
+    }
+}
+
+struct FmtArguments {
+    named: BTreeSet<IdentUnraw>,
+    first_unnamed: Option<TokenStream>,
+}
+
+#[allow(clippy::unnecessary_wraps)]
+fn explicit_named_args(input: ParseStream) -> Result<FmtArguments> {
+    let ahead = input.fork();
+    if let Ok(set) = try_explicit_named_args(&ahead) {
+        input.advance_to(&ahead);
+        return Ok(set);
+    }
+
+    let ahead = input.fork();
+    if let Ok(set) = fallback_explicit_named_args(&ahead) {
+        input.advance_to(&ahead);
+        return Ok(set);
+    }
+
+    input.parse::<TokenStream>().unwrap();
+    Ok(FmtArguments {
+        named: BTreeSet::new(),
+        first_unnamed: None,
+    })
+}
+
+fn try_explicit_named_args(input: ParseStream) -> Result<FmtArguments> {
+    let mut syn_full = None;
+    let mut args = FmtArguments {
+        named: BTreeSet::new(),
+        first_unnamed: None,
+    };
+
+    while !input.is_empty() {
+        input.parse::<Token![,]>()?;
+        if input.is_empty() {
+            break;
+        }
+
+        let mut begin_unnamed = None;
+        if input.peek(Ident::peek_any) && input.peek2(Token![=]) && !input.peek2(Token![==]) {
+            let ident: IdentUnraw = input.parse()?;
+            input.parse::<Token![=]>()?;
+            args.named.insert(ident);
+        } else {
+            begin_unnamed = Some(input.fork());
+        }
+
+        let ahead = input.fork();
+        if *syn_full.get_or_insert_with(is_syn_full) && ahead.parse::<Expr>().is_ok() {
+            input.advance_to(&ahead);
+        } else {
+            scan_expr(input)?;
+        }
+
+        if let Some(begin_unnamed) = begin_unnamed {
+            if args.first_unnamed.is_none() {
+                args.first_unnamed = Some(between(&begin_unnamed, input));
+            }
+        }
+    }
+
+    Ok(args)
+}
+
+fn fallback_explicit_named_args(input: ParseStream) -> Result<FmtArguments> {
+    let mut args = FmtArguments {
+        named: BTreeSet::new(),
+        first_unnamed: None,
+    };
+
+    while !input.is_empty() {
+        if input.peek(Token![,])
+            && input.peek2(Ident::peek_any)
+            && input.peek3(Token![=])
+            && !input.peek3(Token![==])
+        {
+            input.parse::<Token![,]>()?;
+            let ident: IdentUnraw = input.parse()?;
+            input.parse::<Token![=]>()?;
+            args.named.insert(ident);
+        } else {
+            input.parse::<TokenTree>()?;
+        }
+    }
+
+    Ok(args)
+}
+
+fn is_syn_full() -> bool {
+    // Expr::Block contains syn::Block which contains Vec<syn::Stmt>. In the
+    // current version of Syn, syn::Stmt is exhaustive and could only plausibly
+    // represent `trait Trait {}` in Stmt::Item which contains syn::Item. Most
+    // of the point of syn's non-"full" mode is to avoid compiling Item and the
+    // entire expansive syntax tree it comprises. So the following expression
+    // being parsed to Expr::Block is a reliable indication that "full" is
+    // enabled.
+    let test = quote!({
+        trait Trait {}
+    });
+    match syn::parse2(test) {
+        Ok(Expr::Verbatim(_)) | Err(_) => false,
+        Ok(Expr::Block(_)) => true,
+        Ok(_) => unreachable!(),
+    }
+}
+
+fn take_int<'a>(read: &mut &'a str) -> &'a str {
+    let mut int_len = 0;
+    for ch in read.chars() {
+        match ch {
+            '0'..='9' => int_len += 1,
+            _ => break,
+        }
+    }
+    let (int, rest) = read.split_at(int_len);
+    *read = rest;
+    int
+}
+
+fn take_ident<'a>(read: &mut &'a str) -> &'a str {
+    let mut ident_len = 0;
+    for ch in read.chars() {
+        match ch {
+            'a'..='z' | 'A'..='Z' | '0'..='9' | '_' => ident_len += 1,
+            _ => break,
+        }
+    }
+    let (ident, rest) = read.split_at(ident_len);
+    *read = rest;
+    ident
+}
+
+fn between<'a>(begin: ParseStream<'a>, end: ParseStream<'a>) -> TokenStream {
+    let end = end.cursor();
+    let mut cursor = begin.cursor();
+    let mut tokens = TokenStream::new();
+
+    while cursor < end {
+        let (tt, next) = cursor.token_tree().unwrap();
+
+        if end < next {
+            if let Some((inside, _span, _after)) = cursor.group(Delimiter::None) {
+                cursor = inside;
+                continue;
+            }
+            if tokens.is_empty() {
+                tokens.extend(iter::once(tt));
+            }
+            break;
+        }
+
+        tokens.extend(iter::once(tt));
+        cursor = next;
+    }
+
+    tokens
+}
diff --git a/subprojects/thiserror/impl/src/generics.rs b/subprojects/thiserror/impl/src/generics.rs
new file mode 100644
index 0000000..26fe0a9
--- /dev/null
+++ b/subprojects/thiserror/impl/src/generics.rs
@@ -0,0 +1,83 @@
+use proc_macro2::TokenStream;
+use quote::ToTokens;
+use std::collections::btree_map::Entry;
+use std::collections::{BTreeMap as Map, BTreeSet as Set};
+use syn::punctuated::Punctuated;
+use syn::{parse_quote, GenericArgument, Generics, Ident, PathArguments, Token, Type, WhereClause};
+
+pub struct ParamsInScope<'a> {
+    names: Set<&'a Ident>,
+}
+
+impl<'a> ParamsInScope<'a> {
+    pub fn new(generics: &'a Generics) -> Self {
+        ParamsInScope {
+            names: generics.type_params().map(|param| &param.ident).collect(),
+        }
+    }
+
+    pub fn intersects(&self, ty: &Type) -> bool {
+        let mut found = false;
+        crawl(self, ty, &mut found);
+        found
+    }
+}
+
+fn crawl(in_scope: &ParamsInScope, ty: &Type, found: &mut bool) {
+    if let Type::Path(ty) = ty {
+        if let Some(qself) = &ty.qself {
+            crawl(in_scope, &qself.ty, found);
+        } else {
+            let front = ty.path.segments.first().unwrap();
+            if front.arguments.is_none() && in_scope.names.contains(&front.ident) {
+                *found = true;
+            }
+        }
+        for segment in &ty.path.segments {
+            if let PathArguments::AngleBracketed(arguments) = &segment.arguments {
+                for arg in &arguments.args {
+                    if let GenericArgument::Type(ty) = arg {
+                        crawl(in_scope, ty, found);
+                    }
+                }
+            }
+        }
+    }
+}
+
+pub struct InferredBounds {
+    bounds: Map<String, (Set<String>, Punctuated<TokenStream, Token![+]>)>,
+    order: Vec<TokenStream>,
+}
+
+impl InferredBounds {
+    pub fn new() -> Self {
+        InferredBounds {
+            bounds: Map::new(),
+            order: Vec::new(),
+        }
+    }
+
+    pub fn insert(&mut self, ty: impl ToTokens, bound: impl ToTokens) {
+        let ty = ty.to_token_stream();
+        let bound = bound.to_token_stream();
+        let entry = self.bounds.entry(ty.to_string());
+        if let Entry::Vacant(_) = entry {
+            self.order.push(ty);
+        }
+        let (set, tokens) = entry.or_default();
+        if set.insert(bound.to_string()) {
+            tokens.push(bound);
+        }
+    }
+
+    pub fn augment_where_clause(&self, generics: &Generics) -> WhereClause {
+        let mut generics = generics.clone();
+        let where_clause = generics.make_where_clause();
+        for ty in &self.order {
+            let (_set, bounds) = &self.bounds[&ty.to_string()];
+            where_clause.predicates.push(parse_quote!(#ty: #bounds));
+        }
+        generics.where_clause.unwrap()
+    }
+}
diff --git a/subprojects/thiserror/impl/src/lib.rs b/subprojects/thiserror/impl/src/lib.rs
new file mode 100644
index 0000000..25890f2
--- /dev/null
+++ b/subprojects/thiserror/impl/src/lib.rs
@@ -0,0 +1,55 @@
+#![allow(
+    clippy::blocks_in_conditions,
+    clippy::cast_lossless,
+    clippy::cast_possible_truncation,
+    clippy::enum_glob_use,
+    clippy::expl_impl_clone_on_copy, // https://github.com/rust-lang/rust-clippy/issues/15842
+    clippy::manual_find,
+    clippy::manual_let_else,
+    clippy::manual_map,
+    clippy::map_unwrap_or,
+    clippy::module_name_repetitions,
+    clippy::needless_pass_by_value,
+    clippy::range_plus_one,
+    clippy::single_match_else,
+    clippy::struct_field_names,
+    clippy::too_many_lines,
+    clippy::wrong_self_convention
+)]
+#![allow(unknown_lints, mismatched_lifetime_syntaxes)]
+
+extern crate proc_macro;
+
+mod ast;
+mod attr;
+mod expand;
+mod fallback;
+mod fmt;
+mod generics;
+mod prop;
+mod scan_expr;
+mod unraw;
+mod valid;
+
+use proc_macro::TokenStream;
+use proc_macro2::{Ident, Span};
+use quote::{ToTokens, TokenStreamExt as _};
+use syn::{parse_macro_input, DeriveInput};
+
+#[proc_macro_derive(Error, attributes(backtrace, error, from, source))]
+pub fn derive_error(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    expand::derive(&input).into()
+}
+
+#[allow(non_camel_case_types)]
+struct private;
+
+impl ToTokens for private {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        tokens.append(Ident::new(
+            concat!("__private", env!("CARGO_PKG_VERSION_PATCH")),
+            Span::call_site(),
+        ));
+    }
+}
diff --git a/subprojects/thiserror/impl/src/prop.rs b/subprojects/thiserror/impl/src/prop.rs
new file mode 100644
index 0000000..0a101fc
--- /dev/null
+++ b/subprojects/thiserror/impl/src/prop.rs
@@ -0,0 +1,148 @@
+use crate::ast::{Enum, Field, Struct, Variant};
+use crate::unraw::MemberUnraw;
+use proc_macro2::Span;
+use syn::Type;
+
+impl Struct<'_> {
+    pub(crate) fn from_field(&self) -> Option<&Field> {
+        from_field(&self.fields)
+    }
+
+    pub(crate) fn source_field(&self) -> Option<&Field> {
+        source_field(&self.fields)
+    }
+
+    pub(crate) fn backtrace_field(&self) -> Option<&Field> {
+        backtrace_field(&self.fields)
+    }
+
+    pub(crate) fn distinct_backtrace_field(&self) -> Option<&Field> {
+        let backtrace_field = self.backtrace_field()?;
+        distinct_backtrace_field(backtrace_field, self.from_field())
+    }
+}
+
+impl Enum<'_> {
+    pub(crate) fn has_source(&self) -> bool {
+        self.variants
+            .iter()
+            .any(|variant| variant.source_field().is_some() || variant.attrs.transparent.is_some())
+    }
+
+    pub(crate) fn has_backtrace(&self) -> bool {
+        self.variants
+            .iter()
+            .any(|variant| variant.backtrace_field().is_some())
+    }
+
+    pub(crate) fn has_display(&self) -> bool {
+        self.attrs.display.is_some()
+            || self.attrs.transparent.is_some()
+            || self.attrs.fmt.is_some()
+            || self
+                .variants
+                .iter()
+                .any(|variant| variant.attrs.display.is_some() || variant.attrs.fmt.is_some())
+            || self
+                .variants
+                .iter()
+                .all(|variant| variant.attrs.transparent.is_some())
+    }
+}
+
+impl Variant<'_> {
+    pub(crate) fn from_field(&self) -> Option<&Field> {
+        from_field(&self.fields)
+    }
+
+    pub(crate) fn source_field(&self) -> Option<&Field> {
+        source_field(&self.fields)
+    }
+
+    pub(crate) fn backtrace_field(&self) -> Option<&Field> {
+        backtrace_field(&self.fields)
+    }
+
+    pub(crate) fn distinct_backtrace_field(&self) -> Option<&Field> {
+        let backtrace_field = self.backtrace_field()?;
+        distinct_backtrace_field(backtrace_field, self.from_field())
+    }
+}
+
+impl Field<'_> {
+    pub(crate) fn is_backtrace(&self) -> bool {
+        type_is_backtrace(self.ty)
+    }
+
+    pub(crate) fn source_span(&self) -> Span {
+        if let Some(source_attr) = &self.attrs.source {
+            source_attr.span
+        } else if let Some(from_attr) = &self.attrs.from {
+            from_attr.span
+        } else {
+            self.member.span()
+        }
+    }
+}
+
+fn from_field<'a, 'b>(fields: &'a [Field<'b>]) -> Option<&'a Field<'b>> {
+    for field in fields {
+        if field.attrs.from.is_some() {
+            return Some(field);
+        }
+    }
+    None
+}
+
+fn source_field<'a, 'b>(fields: &'a [Field<'b>]) -> Option<&'a Field<'b>> {
+    for field in fields {
+        if field.attrs.from.is_some() || field.attrs.source.is_some() {
+            return Some(field);
+        }
+    }
+    for field in fields {
+        match &field.member {
+            MemberUnraw::Named(ident) if ident == "source" => return Some(field),
+            _ => {}
+        }
+    }
+    None
+}
+
+fn backtrace_field<'a, 'b>(fields: &'a [Field<'b>]) -> Option<&'a Field<'b>> {
+    for field in fields {
+        if field.attrs.backtrace.is_some() {
+            return Some(field);
+        }
+    }
+    for field in fields {
+        if field.is_backtrace() {
+            return Some(field);
+        }
+    }
+    None
+}
+
+// The #[backtrace] field, if it is not the same as the #[from] field.
+fn distinct_backtrace_field<'a, 'b>(
+    backtrace_field: &'a Field<'b>,
+    from_field: Option<&Field>,
+) -> Option<&'a Field<'b>> {
+    if from_field.map_or(false, |from_field| {
+        from_field.member == backtrace_field.member
+    }) {
+        None
+    } else {
+        Some(backtrace_field)
+    }
+}
+
+fn type_is_backtrace(ty: &Type) -> bool {
+    let path = match ty {
+        Type::Path(ty) => &ty.path,
+        _ => return false,
+    };
+
+    let last = path.segments.last().unwrap();
+    last.ident == "Backtrace" && last.arguments.is_empty()
+}
diff --git a/subprojects/thiserror/impl/src/scan_expr.rs b/subprojects/thiserror/impl/src/scan_expr.rs
new file mode 100644
index 0000000..155b5b6
--- /dev/null
+++ b/subprojects/thiserror/impl/src/scan_expr.rs
@@ -0,0 +1,264 @@
+use self::{Action::*, Input::*};
+use proc_macro2::{Delimiter, Ident, Spacing, TokenTree};
+use syn::parse::{ParseStream, Result};
+use syn::{AngleBracketedGenericArguments, BinOp, Expr, ExprPath, Lifetime, Lit, Token, Type};
+
+enum Input {
+    Keyword(&'static str),
+    Punct(&'static str),
+    ConsumeAny,
+    ConsumeBinOp,
+    ConsumeBrace,
+    ConsumeDelimiter,
+    ConsumeIdent,
+    ConsumeLifetime,
+    ConsumeLiteral,
+    ConsumeNestedBrace,
+    ExpectPath,
+    ExpectTurbofish,
+    ExpectType,
+    CanBeginExpr,
+    Otherwise,
+    Empty,
+}
+
+enum Action {
+    SetState(&'static [(Input, Action)]),
+    IncDepth,
+    DecDepth,
+    Finish,
+}
+
+static INIT: [(Input, Action); 28] = [
+    (ConsumeDelimiter, SetState(&POSTFIX)),
+    (Keyword("async"), SetState(&ASYNC)),
+    (Keyword("break"), SetState(&BREAK_LABEL)),
+    (Keyword("const"), SetState(&CONST)),
+    (Keyword("continue"), SetState(&CONTINUE)),
+    (Keyword("for"), SetState(&FOR)),
+    (Keyword("if"), IncDepth),
+    (Keyword("let"), SetState(&PATTERN)),
+    (Keyword("loop"), SetState(&BLOCK)),
+    (Keyword("match"), IncDepth),
+    (Keyword("move"), SetState(&CLOSURE)),
+    (Keyword("return"), SetState(&RETURN)),
+    (Keyword("static"), SetState(&CLOSURE)),
+    (Keyword("unsafe"), SetState(&BLOCK)),
+    (Keyword("while"), IncDepth),
+    (Keyword("yield"), SetState(&RETURN)),
+    (Keyword("_"), SetState(&POSTFIX)),
+    (Punct("!"), SetState(&INIT)),
+    (Punct("#"), SetState(&[(ConsumeDelimiter, SetState(&INIT))])),
+    (Punct("&"), SetState(&REFERENCE)),
+    (Punct("*"), SetState(&INIT)),
+    (Punct("-"), SetState(&INIT)),
+    (Punct("..="), SetState(&INIT)),
+    (Punct(".."), SetState(&RANGE)),
+    (Punct("|"), SetState(&CLOSURE_ARGS)),
+    (ConsumeLifetime, SetState(&[(Punct(":"), SetState(&INIT))])),
+    (ConsumeLiteral, SetState(&POSTFIX)),
+    (ExpectPath, SetState(&PATH)),
+];
+
+static POSTFIX: [(Input, Action); 10] = [
+    (Keyword("as"), SetState(&[(ExpectType, SetState(&POSTFIX))])),
+    (Punct("..="), SetState(&INIT)),
+    (Punct(".."), SetState(&RANGE)),
+    (Punct("."), SetState(&DOT)),
+    (Punct("?"), SetState(&POSTFIX)),
+    (ConsumeBinOp, SetState(&INIT)),
+    (Punct("="), SetState(&INIT)),
+    (ConsumeNestedBrace, SetState(&IF_THEN)),
+    (ConsumeDelimiter, SetState(&POSTFIX)),
+    (Empty, Finish),
+];
+
+static ASYNC: [(Input, Action); 3] = [
+    (Keyword("move"), SetState(&ASYNC)),
+    (Punct("|"), SetState(&CLOSURE_ARGS)),
+    (ConsumeBrace, SetState(&POSTFIX)),
+];
+
+static BLOCK: [(Input, Action); 1] = [(ConsumeBrace, SetState(&POSTFIX))];
+
+static BREAK_LABEL: [(Input, Action); 2] = [
+    (ConsumeLifetime, SetState(&BREAK_VALUE)),
+    (Otherwise, SetState(&BREAK_VALUE)),
+];
+
+static BREAK_VALUE: [(Input, Action); 3] = [
+    (ConsumeNestedBrace, SetState(&IF_THEN)),
+    (CanBeginExpr, SetState(&INIT)),
+    (Otherwise, SetState(&POSTFIX)),
+];
+
+static CLOSURE: [(Input, Action); 6] = [
+    (Keyword("async"), SetState(&CLOSURE)),
+    (Keyword("move"), SetState(&CLOSURE)),
+    (Punct(","), SetState(&CLOSURE)),
+    (Punct(">"), SetState(&CLOSURE)),
+    (Punct("|"), SetState(&CLOSURE_ARGS)),
+    (ConsumeLifetime, SetState(&CLOSURE)),
+];
+
+static CLOSURE_ARGS: [(Input, Action); 2] = [
+    (Punct("|"), SetState(&CLOSURE_RET)),
+    (ConsumeAny, SetState(&CLOSURE_ARGS)),
+];
+
+static CLOSURE_RET: [(Input, Action); 2] = [
+    (Punct("->"), SetState(&[(ExpectType, SetState(&BLOCK))])),
+    (Otherwise, SetState(&INIT)),
+];
+
+static CONST: [(Input, Action); 2] = [
+    (Punct("|"), SetState(&CLOSURE_ARGS)),
+    (ConsumeBrace, SetState(&POSTFIX)),
+];
+
+static CONTINUE: [(Input, Action); 2] = [
+    (ConsumeLifetime, SetState(&POSTFIX)),
+    (Otherwise, SetState(&POSTFIX)),
+];
+
+static DOT: [(Input, Action); 3] = [
+    (Keyword("await"), SetState(&POSTFIX)),
+    (ConsumeIdent, SetState(&METHOD)),
+    (ConsumeLiteral, SetState(&POSTFIX)),
+];
+
+static FOR: [(Input, Action); 2] = [
+    (Punct("<"), SetState(&CLOSURE)),
+    (Otherwise, SetState(&PATTERN)),
+];
+
+static IF_ELSE: [(Input, Action); 2] = [(Keyword("if"), SetState(&INIT)), (ConsumeBrace, DecDepth)];
+static IF_THEN: [(Input, Action); 2] =
+    [(Keyword("else"), SetState(&IF_ELSE)), (Otherwise, DecDepth)];
+
+static METHOD: [(Input, Action); 1] = [(ExpectTurbofish, SetState(&POSTFIX))];
+
+static PATH: [(Input, Action); 4] = [
+    (Punct("!="), SetState(&INIT)),
+    (Punct("!"), SetState(&INIT)),
+    (ConsumeNestedBrace, SetState(&IF_THEN)),
+    (Otherwise, SetState(&POSTFIX)),
+];
+
+static PATTERN: [(Input, Action); 15] = [
+    (ConsumeDelimiter, SetState(&PATTERN)),
+    (Keyword("box"), SetState(&PATTERN)),
+    (Keyword("in"), IncDepth),
+    (Keyword("mut"), SetState(&PATTERN)),
+    (Keyword("ref"), SetState(&PATTERN)),
+    (Keyword("_"), SetState(&PATTERN)),
+    (Punct("!"), SetState(&PATTERN)),
+    (Punct("&"), SetState(&PATTERN)),
+    (Punct("..="), SetState(&PATTERN)),
+    (Punct(".."), SetState(&PATTERN)),
+    (Punct("="), SetState(&INIT)),
+    (Punct("@"), SetState(&PATTERN)),
+    (Punct("|"), SetState(&PATTERN)),
+    (ConsumeLiteral, SetState(&PATTERN)),
+    (ExpectPath, SetState(&PATTERN)),
+];
+
+static RANGE: [(Input, Action); 6] = [
+    (Punct("..="), SetState(&INIT)),
+    (Punct(".."), SetState(&RANGE)),
+    (Punct("."), SetState(&DOT)),
+    (ConsumeNestedBrace, SetState(&IF_THEN)),
+    (Empty, Finish),
+    (Otherwise, SetState(&INIT)),
+];
+
+static RAW: [(Input, Action); 3] = [
+    (Keyword("const"), SetState(&INIT)),
+    (Keyword("mut"), SetState(&INIT)),
+    (Otherwise, SetState(&POSTFIX)),
+];
+
+static REFERENCE: [(Input, Action); 3] = [
+    (Keyword("mut"), SetState(&INIT)),
+    (Keyword("raw"), SetState(&RAW)),
+    (Otherwise, SetState(&INIT)),
+];
+
+static RETURN: [(Input, Action); 2] = [
+    (CanBeginExpr, SetState(&INIT)),
+    (Otherwise, SetState(&POSTFIX)),
+];
+
+pub(crate) fn scan_expr(input: ParseStream) -> Result<()> {
+    let mut state = INIT.as_slice();
+    let mut depth = 0usize;
+    'table: loop {
+        for rule in state {
+            if match rule.0 {
+                Input::Keyword(expected) => input.step(|cursor| match cursor.ident() {
+                    Some((ident, rest)) if ident == expected => Ok((true, rest)),
+                    _ => Ok((false, *cursor)),
+                })?,
+                Input::Punct(expected) => input.step(|cursor| {
+                    let begin = *cursor;
+                    let mut cursor = begin;
+                    for (i, ch) in expected.chars().enumerate() {
+                        match cursor.punct() {
+                            Some((punct, _)) if punct.as_char() != ch => break,
+                            Some((_, rest)) if i == expected.len() - 1 => {
+                                return Ok((true, rest));
+                            }
+                            Some((punct, rest)) if punct.spacing() == Spacing::Joint => {
+                                cursor = rest;
+                            }
+                            _ => break,
+                        }
+                    }
+                    Ok((false, begin))
+                })?,
+                Input::ConsumeAny => input.parse::<Option<TokenTree>>()?.is_some(),
+                Input::ConsumeBinOp => input.parse::<BinOp>().is_ok(),
+                Input::ConsumeBrace | Input::ConsumeNestedBrace => {
+                    (matches!(rule.0, Input::ConsumeBrace) || depth > 0)
+                        && input.step(|cursor| match cursor.group(Delimiter::Brace) {
+                            Some((_inside, _span, rest)) => Ok((true, rest)),
+                            None => Ok((false, *cursor)),
+                        })?
+                }
+                Input::ConsumeDelimiter => input.step(|cursor| match cursor.any_group() {
+                    Some((_inside, _delimiter, _span, rest)) => Ok((true, rest)),
+                    None => Ok((false, *cursor)),
+                })?,
+                Input::ConsumeIdent => input.parse::<Option<Ident>>()?.is_some(),
+                Input::ConsumeLifetime => input.parse::<Option<Lifetime>>()?.is_some(),
+                Input::ConsumeLiteral => input.parse::<Option<Lit>>()?.is_some(),
+                Input::ExpectPath => {
+                    input.parse::<ExprPath>()?;
+                    true
+                }
+                Input::ExpectTurbofish => {
+                    if input.peek(Token![::]) {
+                        input.parse::<AngleBracketedGenericArguments>()?;
+                    }
+                    true
+                }
+                Input::ExpectType => {
+                    Type::without_plus(input)?;
+                    true
+                }
+                Input::CanBeginExpr => Expr::peek(input),
+                Input::Otherwise => true,
+                Input::Empty => input.is_empty() || input.peek(Token![,]),
+            } {
+                state = match rule.1 {
+                    Action::SetState(next) => next,
+                    Action::IncDepth => (depth += 1, &INIT).1,
+                    Action::DecDepth => (depth -= 1, &POSTFIX).1,
+                    Action::Finish => return if depth == 0 { Ok(()) } else { break },
+                };
+                continue 'table;
+            }
+        }
+        return Err(input.error("unsupported expression"));
+    }
+}
diff --git a/subprojects/thiserror/impl/src/unraw.rs b/subprojects/thiserror/impl/src/unraw.rs
new file mode 100644
index 0000000..73b9970
--- /dev/null
+++ b/subprojects/thiserror/impl/src/unraw.rs
@@ -0,0 +1,142 @@
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::ToTokens;
+use std::cmp::Ordering;
+use std::fmt::{self, Display};
+use std::hash::{Hash, Hasher};
+use syn::ext::IdentExt as _;
+use syn::parse::{Parse, ParseStream, Result};
+use syn::Index;
+
+#[derive(Clone)]
+#[repr(transparent)]
+pub struct IdentUnraw(Ident);
+
+impl IdentUnraw {
+    pub fn new(ident: Ident) -> Self {
+        IdentUnraw(ident)
+    }
+
+    pub fn to_local(&self) -> Ident {
+        let unraw = self.0.unraw();
+        let repr = unraw.to_string();
+        if syn::parse_str::<Ident>(&repr).is_err() {
+            if let "_" | "super" | "self" | "Self" | "crate" = repr.as_str() {
+                // Some identifiers are never allowed to appear as raw, like r#self and r#_.
+            } else {
+                return Ident::new_raw(&repr, Span::call_site());
+            }
+        }
+        unraw
+    }
+
+    pub fn set_span(&mut self, span: Span) {
+        self.0.set_span(span);
+    }
+}
+
+impl Display for IdentUnraw {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        Display::fmt(&self.0.unraw(), formatter)
+    }
+}
+
+impl Eq for IdentUnraw {}
+
+impl PartialEq for IdentUnraw {
+    fn eq(&self, other: &Self) -> bool {
+        PartialEq::eq(&self.0.unraw(), &other.0.unraw())
+    }
+}
+
+impl PartialEq<str> for IdentUnraw {
+    fn eq(&self, other: &str) -> bool {
+        self.0 == other
+    }
+}
+
+impl Ord for IdentUnraw {
+    fn cmp(&self, other: &Self) -> Ordering {
+        Ord::cmp(&self.0.unraw(), &other.0.unraw())
+    }
+}
+
+impl PartialOrd for IdentUnraw {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(Self::cmp(self, other))
+    }
+}
+
+impl Parse for IdentUnraw {
+    fn parse(input: ParseStream) -> Result<Self> {
+        input.call(Ident::parse_any).map(IdentUnraw::new)
+    }
+}
+
+impl ToTokens for IdentUnraw {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        self.0.unraw().to_tokens(tokens);
+    }
+}
+
+#[derive(Clone)]
+pub enum MemberUnraw {
+    Named(IdentUnraw),
+    Unnamed(Index),
+}
+
+impl MemberUnraw {
+    pub fn span(&self) -> Span {
+        match self {
+            MemberUnraw::Named(ident) => ident.0.span(),
+            MemberUnraw::Unnamed(index) => index.span,
+        }
+    }
+}
+
+impl Display for MemberUnraw {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            MemberUnraw::Named(this) => Display::fmt(this, formatter),
+            MemberUnraw::Unnamed(this) => Display::fmt(&this.index, formatter),
+        }
+    }
+}
+
+impl Eq for MemberUnraw {}
+
+impl PartialEq for MemberUnraw {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (MemberUnraw::Named(this), MemberUnraw::Named(other)) => this == other,
+            (MemberUnraw::Unnamed(this), MemberUnraw::Unnamed(other)) => this == other,
+            _ => false,
+        }
+    }
+}
+
+impl PartialEq<str> for MemberUnraw {
+    fn eq(&self, other: &str) -> bool {
+        match self {
+            MemberUnraw::Named(this) => this == other,
+            MemberUnraw::Unnamed(_) => false,
+        }
+    }
+}
+
+impl Hash for MemberUnraw {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        match self {
+            MemberUnraw::Named(ident) => ident.0.unraw().hash(hasher),
+            MemberUnraw::Unnamed(index) => index.hash(hasher),
+        }
+    }
+}
+
+impl ToTokens for MemberUnraw {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        match self {
+            MemberUnraw::Named(ident) => ident.to_local().to_tokens(tokens),
+            MemberUnraw::Unnamed(index) => index.to_tokens(tokens),
+        }
+    }
+}
diff --git a/subprojects/thiserror/impl/src/valid.rs b/subprojects/thiserror/impl/src/valid.rs
new file mode 100644
index 0000000..21bd885
--- /dev/null
+++ b/subprojects/thiserror/impl/src/valid.rs
@@ -0,0 +1,248 @@
+use crate::ast::{Enum, Field, Input, Struct, Variant};
+use crate::attr::Attrs;
+use syn::{Error, GenericArgument, PathArguments, Result, Type};
+
+impl Input<'_> {
+    pub(crate) fn validate(&self) -> Result<()> {
+        match self {
+            Input::Struct(input) => input.validate(),
+            Input::Enum(input) => input.validate(),
+        }
+    }
+}
+
+impl Struct<'_> {
+    fn validate(&self) -> Result<()> {
+        check_non_field_attrs(&self.attrs)?;
+        if let Some(transparent) = self.attrs.transparent {
+            if self.fields.len() != 1 {
+                return Err(Error::new_spanned(
+                    transparent.original,
+                    "#[error(transparent)] requires exactly one field",
+                ));
+            }
+            if let Some(source) = self.fields.iter().find_map(|f| f.attrs.source) {
+                return Err(Error::new_spanned(
+                    source.original,
+                    "transparent error struct can't contain #[source]",
+                ));
+            }
+        }
+        if let Some(fmt) = &self.attrs.fmt {
+            return Err(Error::new_spanned(
+                fmt.original,
+                "#[error(fmt = ...)] is only supported in enums; for a struct, handwrite your own Display impl",
+            ));
+        }
+        check_field_attrs(&self.fields)?;
+        for field in &self.fields {
+            field.validate()?;
+        }
+        Ok(())
+    }
+}
+
+impl Enum<'_> {
+    fn validate(&self) -> Result<()> {
+        check_non_field_attrs(&self.attrs)?;
+        let has_display = self.has_display();
+        for variant in &self.variants {
+            variant.validate()?;
+            if has_display
+                && variant.attrs.display.is_none()
+                && variant.attrs.transparent.is_none()
+                && variant.attrs.fmt.is_none()
+            {
+                return Err(Error::new_spanned(
+                    variant.original,
+                    "missing #[error(\"...\")] display attribute",
+                ));
+            }
+        }
+        Ok(())
+    }
+}
+
+impl Variant<'_> {
+    fn validate(&self) -> Result<()> {
+        check_non_field_attrs(&self.attrs)?;
+        if self.attrs.transparent.is_some() {
+            if self.fields.len() != 1 {
+                return Err(Error::new_spanned(
+                    self.original,
+                    "#[error(transparent)] requires exactly one field",
+                ));
+            }
+            if let Some(source) = self.fields.iter().find_map(|f| f.attrs.source) {
+                return Err(Error::new_spanned(
+                    source.original,
+                    "transparent variant can't contain #[source]",
+                ));
+            }
+        }
+        check_field_attrs(&self.fields)?;
+        for field in &self.fields {
+            field.validate()?;
+        }
+        Ok(())
+    }
+}
+
+impl Field<'_> {
+    fn validate(&self) -> Result<()> {
+        if let Some(unexpected_display_attr) = if let Some(display) = &self.attrs.display {
+            Some(display.original)
+        } else if let Some(fmt) = &self.attrs.fmt {
+            Some(fmt.original)
+        } else {
+            None
+        } {
+            return Err(Error::new_spanned(
+                unexpected_display_attr,
+                "not expected here; the #[error(...)] attribute belongs on top of a struct or an enum variant",
+            ));
+        }
+        Ok(())
+    }
+}
+
+fn check_non_field_attrs(attrs: &Attrs) -> Result<()> {
+    if let Some(from) = &attrs.from {
+        return Err(Error::new_spanned(
+            from.original,
+            "not expected here; the #[from] attribute belongs on a specific field",
+        ));
+    }
+    if let Some(source) = &attrs.source {
+        return Err(Error::new_spanned(
+            source.original,
+            "not expected here; the #[source] attribute belongs on a specific field",
+        ));
+    }
+    if let Some(backtrace) = &attrs.backtrace {
+        return Err(Error::new_spanned(
+            backtrace,
+            "not expected here; the #[backtrace] attribute belongs on a specific field",
+        ));
+    }
+    if attrs.transparent.is_some() {
+        if let Some(display) = &attrs.display {
+            return Err(Error::new_spanned(
+                display.original,
+                "cannot have both #[error(transparent)] and a display attribute",
+            ));
+        }
+        if let Some(fmt) = &attrs.fmt {
+            return Err(Error::new_spanned(
+                fmt.original,
+                "cannot have both #[error(transparent)] and #[error(fmt = ...)]",
+            ));
+        }
+    } else if let (Some(display), Some(_)) = (&attrs.display, &attrs.fmt) {
+        return Err(Error::new_spanned(
+            display.original,
+            "cannot have both #[error(fmt = ...)] and a format arguments attribute",
+        ));
+    }
+
+    Ok(())
+}
+
+fn check_field_attrs(fields: &[Field]) -> Result<()> {
+    let mut from_field = None;
+    let mut source_field = None;
+    let mut backtrace_field = None;
+    let mut has_backtrace = false;
+    for field in fields {
+        if let Some(from) = field.attrs.from {
+            if from_field.is_some() {
+                return Err(Error::new_spanned(
+                    from.original,
+                    "duplicate #[from] attribute",
+                ));
+            }
+            from_field = Some(field);
+        }
+        if let Some(source) = field.attrs.source {
+            if source_field.is_some() {
+                return Err(Error::new_spanned(
+                    source.original,
+                    "duplicate #[source] attribute",
+                ));
+            }
+            source_field = Some(field);
+        }
+        if let Some(backtrace) = field.attrs.backtrace {
+            if backtrace_field.is_some() {
+                return Err(Error::new_spanned(
+                    backtrace,
+                    "duplicate #[backtrace] attribute",
+                ));
+            }
+            backtrace_field = Some(field);
+            has_backtrace = true;
+        }
+        if let Some(transparent) = field.attrs.transparent {
+            return Err(Error::new_spanned(
+                transparent.original,
+                "#[error(transparent)] needs to go outside the enum or struct, not on an individual field",
+            ));
+        }
+        has_backtrace |= field.is_backtrace();
+    }
+    if let (Some(from_field), Some(source_field)) = (from_field, source_field) {
+        if from_field.member != source_field.member {
+            return Err(Error::new_spanned(
+                from_field.attrs.from.unwrap().original,
+                "#[from] is only supported on the source field, not any other field",
+            ));
+        }
+    }
+    if let Some(from_field) = from_field {
+        let max_expected_fields = match backtrace_field {
+            Some(backtrace_field) => 1 + (from_field.member != backtrace_field.member) as usize,
+            None => 1 + has_backtrace as usize,
+        };
+        if fields.len() > max_expected_fields {
+            return Err(Error::new_spanned(
+                from_field.attrs.from.unwrap().original,
+                "deriving From requires no fields other than source and backtrace",
+            ));
+        }
+    }
+    if let Some(source_field) = source_field.or(from_field) {
+        if contains_non_static_lifetime(source_field.ty) {
+            return Err(Error::new_spanned(
+                &source_field.original.ty,
+                "non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static",
+            ));
+        }
+    }
+    Ok(())
+}
+
+fn contains_non_static_lifetime(ty: &Type) -> bool {
+    match ty {
+        Type::Path(ty) => {
+            let bracketed = match &ty.path.segments.last().unwrap().arguments {
+                PathArguments::AngleBracketed(bracketed) => bracketed,
+                _ => return false,
+            };
+            for arg in &bracketed.args {
+                match arg {
+                    GenericArgument::Type(ty) if contains_non_static_lifetime(ty) => return true,
+                    GenericArgument::Lifetime(lifetime) if lifetime.ident != "static" => {
+                        return true
+                    }
+                    _ => {}
+                }
+            }
+            false
+        }
+        Type::Reference(ty) => ty
+            .lifetime
+            .as_ref()
+            .map_or(false, |lifetime| lifetime.ident != "static"),
+        _ => false, // maybe implement later if there are common other cases
+    }
+}
diff --git a/subprojects/thiserror/rust-toolchain.toml b/subprojects/thiserror/rust-toolchain.toml
new file mode 100644
index 0000000..20fe888
--- /dev/null
+++ b/subprojects/thiserror/rust-toolchain.toml
@@ -0,0 +1,2 @@
+[toolchain]
+components = ["rust-src"]
diff --git a/subprojects/thiserror/src/aserror.rs b/subprojects/thiserror/src/aserror.rs
new file mode 100644
index 0000000..ac91cc8
--- /dev/null
+++ b/subprojects/thiserror/src/aserror.rs
@@ -0,0 +1,50 @@
+use core::error::Error;
+use core::panic::UnwindSafe;
+
+#[doc(hidden)]
+pub trait AsDynError<'a>: Sealed {
+    fn as_dyn_error(&self) -> &(dyn Error + 'a);
+}
+
+impl<'a, T: Error + 'a> AsDynError<'a> for T {
+    #[inline]
+    fn as_dyn_error(&self) -> &(dyn Error + 'a) {
+        self
+    }
+}
+
+impl<'a> AsDynError<'a> for dyn Error + 'a {
+    #[inline]
+    fn as_dyn_error(&self) -> &(dyn Error + 'a) {
+        self
+    }
+}
+
+impl<'a> AsDynError<'a> for dyn Error + Send + 'a {
+    #[inline]
+    fn as_dyn_error(&self) -> &(dyn Error + 'a) {
+        self
+    }
+}
+
+impl<'a> AsDynError<'a> for dyn Error + Send + Sync + 'a {
+    #[inline]
+    fn as_dyn_error(&self) -> &(dyn Error + 'a) {
+        self
+    }
+}
+
+impl<'a> AsDynError<'a> for dyn Error + Send + Sync + UnwindSafe + 'a {
+    #[inline]
+    fn as_dyn_error(&self) -> &(dyn Error + 'a) {
+        self
+    }
+}
+
+#[doc(hidden)]
+pub trait Sealed {}
+impl<T: Error> Sealed for T {}
+impl Sealed for dyn Error + '_ {}
+impl Sealed for dyn Error + Send + '_ {}
+impl Sealed for dyn Error + Send + Sync + '_ {}
+impl Sealed for dyn Error + Send + Sync + UnwindSafe + '_ {}
diff --git a/subprojects/thiserror/src/display.rs b/subprojects/thiserror/src/display.rs
new file mode 100644
index 0000000..e544657
--- /dev/null
+++ b/subprojects/thiserror/src/display.rs
@@ -0,0 +1,82 @@
+use core::fmt::Display;
+#[cfg(feature = "std")]
+use std::path::{self, Path, PathBuf};
+
+#[doc(hidden)]
+pub trait AsDisplay<'a>: Sealed {
+    // TODO: convert to generic associated type.
+    // https://github.com/dtolnay/thiserror/pull/253
+    type Target: Display;
+
+    fn as_display(&'a self) -> Self::Target;
+}
+
+impl<'a, T> AsDisplay<'a> for &T
+where
+    T: Display + ?Sized + 'a,
+{
+    type Target = &'a T;
+
+    fn as_display(&'a self) -> Self::Target {
+        *self
+    }
+}
+
+#[cfg(feature = "std")]
+impl<'a> AsDisplay<'a> for Path {
+    type Target = path::Display<'a>;
+
+    #[inline]
+    fn as_display(&'a self) -> Self::Target {
+        self.display()
+    }
+}
+
+#[cfg(feature = "std")]
+impl<'a> AsDisplay<'a> for PathBuf {
+    type Target = path::Display<'a>;
+
+    #[inline]
+    fn as_display(&'a self) -> Self::Target {
+        self.display()
+    }
+}
+
+#[doc(hidden)]
+pub trait Sealed {}
+impl<T: Display + ?Sized> Sealed for &T {}
+#[cfg(feature = "std")]
+impl Sealed for Path {}
+#[cfg(feature = "std")]
+impl Sealed for PathBuf {}
+
+// Add a synthetic second impl of AsDisplay to prevent the "single applicable
+// impl" rule from making too weird inference decision based on the single impl
+// for &T, which could lead to code that compiles with thiserror's std feature
+// off but breaks under feature unification when std is turned on by an
+// unrelated crate.
+#[cfg(not(feature = "std"))]
+mod placeholder {
+    use super::{AsDisplay, Sealed};
+    use core::fmt::{self, Display};
+
+    #[allow(dead_code)]
+    pub struct Placeholder;
+
+    impl<'a> AsDisplay<'a> for Placeholder {
+        type Target = Self;
+
+        #[inline]
+        fn as_display(&'a self) -> Self::Target {
+            Placeholder
+        }
+    }
+
+    impl Display for Placeholder {
+        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+            unreachable!()
+        }
+    }
+
+    impl Sealed for Placeholder {}
+}
diff --git a/subprojects/thiserror/src/lib.rs b/subprojects/thiserror/src/lib.rs
new file mode 100644
index 0000000..155272d
--- /dev/null
+++ b/subprojects/thiserror/src/lib.rs
@@ -0,0 +1,291 @@
+//! [![github]](https://github.com/dtolnay/thiserror)&ensp;[![crates-io]](https://crates.io/crates/thiserror)&ensp;[![docs-rs]](https://docs.rs/thiserror)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
+//!
+//! <br>
+//!
+//! This library provides a convenient derive macro for the standard library's
+//! [`std::error::Error`] trait.
+//!
+//! <br>
+//!
+//! # Example
+//!
+//! ```rust
+//! # use std::io;
+//! use thiserror::Error;
+//!
+//! #[derive(Error, Debug)]
+//! pub enum DataStoreError {
+//!     #[error("data store disconnected")]
+//!     Disconnect(#[from] io::Error),
+//!     #[error("the data for key `{0}` is not available")]
+//!     Redaction(String),
+//!     #[error("invalid header (expected {expected:?}, found {found:?})")]
+//!     InvalidHeader {
+//!         expected: String,
+//!         found: String,
+//!     },
+//!     #[error("unknown data store error")]
+//!     Unknown,
+//! }
+//! ```
+//!
+//! <br>
+//!
+//! # Details
+//!
+//! - Thiserror deliberately does not appear in your public API. You get the
+//!   same thing as if you had written an implementation of
+//!   [`std::error::Error`] by hand, and switching from handwritten impls to
+//!   thiserror or vice versa is not a breaking change.
+//!
+//! - Errors may be enums, structs with named fields, tuple structs, or unit
+//!   structs.
+//!
+//! - A [`Display`] impl is generated for your error if you provide
+//!   `#[error("...")]` messages on the struct or each variant of your enum, as
+//!   shown above in the example.
+//!
+//!   The messages support a shorthand for interpolating fields from the error.
+//!
+//!     - `#[error("{var}")]`&ensp;⟶&ensp;`write!("{}", self.var)`
+//!     - `#[error("{0}")]`&ensp;⟶&ensp;`write!("{}", self.0)`
+//!     - `#[error("{var:?}")]`&ensp;⟶&ensp;`write!("{:?}", self.var)`
+//!     - `#[error("{0:?}")]`&ensp;⟶&ensp;`write!("{:?}", self.0)`
+//!
+//!   These shorthands can be used together with any additional format args,
+//!   which may be arbitrary expressions. For example:
+//!
+//!   ```rust
+//!   # use core::i32;
+//!   # use thiserror::Error;
+//!   #
+//!   #[derive(Error, Debug)]
+//!   pub enum Error {
+//!       #[error("invalid rdo_lookahead_frames {0} (expected < {max})", max = i32::MAX)]
+//!       InvalidLookahead(u32),
+//!   }
+//!   ```
+//!
+//!   If one of the additional expression arguments needs to refer to a field of
+//!   the struct or enum, then refer to named fields as `.var` and tuple fields
+//!   as `.0`.
+//!
+//!   ```rust
+//!   # use thiserror::Error;
+//!   #
+//!   # fn first_char(s: &String) -> char {
+//!   #     s.chars().next().unwrap()
+//!   # }
+//!   #
+//!   # #[derive(Debug)]
+//!   # struct Limits {
+//!   #     lo: usize,
+//!   #     hi: usize,
+//!   # }
+//!   #
+//!   #[derive(Error, Debug)]
+//!   pub enum Error {
+//!       #[error("first letter must be lowercase but was {:?}", first_char(.0))]
+//!       WrongCase(String),
+//!       #[error("invalid index {idx}, expected at least {} and at most {}", .limits.lo, .limits.hi)]
+//!       OutOfBounds { idx: usize, limits: Limits },
+//!   }
+//!   ```
+//!
+//! - A [`From`] impl is generated for each variant that contains a `#[from]`
+//!   attribute.
+//!
+//!   The variant using `#[from]` must not contain any other fields beyond the
+//!   source error (and possibly a backtrace &mdash; see below). Usually
+//!   `#[from]` fields are unnamed, but `#[from]` is allowed on a named field
+//!   too.
+//!
+//!   ```rust
+//!   # use core::fmt::{self, Display};
+//!   # use std::io;
+//!   # use thiserror::Error;
+//!   #
+//!   # mod globset {
+//!   #     #[derive(thiserror::Error, Debug)]
+//!   #     #[error("...")]
+//!   #     pub struct Error;
+//!   # }
+//!   #
+//!   #[derive(Error, Debug)]
+//!   pub enum MyError {
+//!       Io(#[from] io::Error),
+//!       Glob(#[from] globset::Error),
+//!   }
+//!   #
+//!   # impl Display for MyError {
+//!   #     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+//!   #         unimplemented!()
+//!   #     }
+//!   # }
+//!   ```
+//!
+//! - The Error trait's [`source()`] method is implemented to return whichever
+//!   field has a `#[source]` attribute or is named `source`, if any. This is
+//!   for identifying the underlying lower level error that caused your error.
+//!
+//!   The `#[from]` attribute always implies that the same field is `#[source]`,
+//!   so you don't ever need to specify both attributes.
+//!
+//!   Any error type that implements `std::error::Error` or dereferences to `dyn
+//!   std::error::Error` will work as a source.
+//!
+//!   ```rust
+//!   # use core::fmt::{self, Display};
+//!   # use thiserror::Error;
+//!   #
+//!   #[derive(Error, Debug)]
+//!   pub struct MyError {
+//!       msg: String,
+//!       #[source]  // optional if field name is `source`
+//!       source: anyhow::Error,
+//!   }
+//!   #
+//!   # impl Display for MyError {
+//!   #     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+//!   #         unimplemented!()
+//!   #     }
+//!   # }
+//!   ```
+//!
+//! - The Error trait's [`provide()`] method is implemented to provide whichever
+//!   field has a type named `Backtrace`, if any, as a
+//!   [`std::backtrace::Backtrace`]. Using `Backtrace` in errors requires a
+//!   nightly compiler with Rust version 1.73 or newer.
+//!
+//!   ```rust
+//!   # const IGNORE: &str = stringify! {
+//!   use std::backtrace::Backtrace;
+//!
+//!   #[derive(Error, Debug)]
+//!   pub struct MyError {
+//!       msg: String,
+//!       backtrace: Backtrace,  // automatically detected
+//!   }
+//!   # };
+//!   ```
+//!
+//! - If a field is both a source (named `source`, or has `#[source]` or
+//!   `#[from]` attribute) *and* is marked `#[backtrace]`, then the Error
+//!   trait's [`provide()`] method is forwarded to the source's `provide` so
+//!   that both layers of the error share the same backtrace. The `#[backtrace]`
+//!   attribute requires a nightly compiler with Rust version 1.73 or newer.
+//!
+//!   ```rust
+//!   # const IGNORE: &str = stringify! {
+//!   #[derive(Error, Debug)]
+//!   pub enum MyError {
+//!       Io {
+//!           #[backtrace]
+//!           source: io::Error,
+//!       },
+//!   }
+//!   # };
+//!   ```
+//!
+//! - For variants that use `#[from]` and also contain a `Backtrace` field, a
+//!   backtrace is captured from within the `From` impl.
+//!
+//!   ```rust
+//!   # const IGNORE: &str = stringify! {
+//!   #[derive(Error, Debug)]
+//!   pub enum MyError {
+//!       Io {
+//!           #[from]
+//!           source: io::Error,
+//!           backtrace: Backtrace,
+//!       },
+//!   }
+//!   # };
+//!   ```
+//!
+//! - Errors may use `error(transparent)` to forward the source and [`Display`]
+//!   methods straight through to an underlying error without adding an
+//!   additional message. This would be appropriate for enums that need an
+//!   "anything else" variant.
+//!
+//!   ```
+//!   # use thiserror::Error;
+//!   #
+//!   #[derive(Error, Debug)]
+//!   pub enum MyError {
+//!       # /*
+//!       ...
+//!       # */
+//!
+//!       #[error(transparent)]
+//!       Other(#[from] anyhow::Error),  // source and Display delegate to anyhow::Error
+//!   }
+//!   ```
+//!
+//!   Another use case is hiding implementation details of an error
+//!   representation behind an opaque error type, so that the representation is
+//!   able to evolve without breaking the crate's public API.
+//!
+//!   ```
+//!   # use thiserror::Error;
+//!   #
+//!   // PublicError is public, but opaque and easy to keep compatible.
+//!   #[derive(Error, Debug)]
+//!   #[error(transparent)]
+//!   pub struct PublicError(#[from] ErrorRepr);
+//!
+//!   impl PublicError {
+//!       // Accessors for anything we do want to expose publicly.
+//!   }
+//!
+//!   // Private and free to change across minor version of the crate.
+//!   #[derive(Error, Debug)]
+//!   enum ErrorRepr {
+//!       # /*
+//!       ...
+//!       # */
+//!   }
+//!   ```
+//!
+//! - See also the [`anyhow`] library for a convenient single error type to use
+//!   in application code.
+//!
+//! [`anyhow`]: https://github.com/dtolnay/anyhow
+//! [`source()`]: std::error::Error::source
+//! [`provide()`]: std::error::Error::provide
+//! [`Display`]: std::fmt::Display
+
+#![no_std]
+#![doc(html_root_url = "https://docs.rs/thiserror/2.0.17")]
+#![allow(
+    clippy::elidable_lifetime_names,
+    clippy::module_name_repetitions,
+    clippy::needless_lifetimes,
+    clippy::return_self_not_must_use,
+    clippy::wildcard_imports
+)]
+#![cfg_attr(error_generic_member_access, feature(error_generic_member_access))]
+
+#[cfg(all(thiserror_nightly_testing, not(error_generic_member_access)))]
+compile_error!("Build script probe failed to compile.");
+
+#[cfg(feature = "std")]
+extern crate std;
+#[cfg(feature = "std")]
+extern crate std as core;
+
+mod aserror;
+mod display;
+#[cfg(error_generic_member_access)]
+mod provide;
+mod var;
+
+pub use thiserror_impl::*;
+
+mod private;
+
+include!(concat!(env!("OUT_DIR"), "/private.rs"));
diff --git a/subprojects/thiserror/src/private.rs b/subprojects/thiserror/src/private.rs
new file mode 100644
index 0000000..545aa8e
--- /dev/null
+++ b/subprojects/thiserror/src/private.rs
@@ -0,0 +1,14 @@
+#[doc(hidden)]
+pub use crate::aserror::AsDynError;
+#[doc(hidden)]
+pub use crate::display::AsDisplay;
+#[cfg(error_generic_member_access)]
+#[doc(hidden)]
+pub use crate::provide::ThiserrorProvide;
+#[doc(hidden)]
+pub use crate::var::Var;
+#[doc(hidden)]
+pub use core::error::Error;
+#[cfg(all(feature = "std", not(thiserror_no_backtrace_type)))]
+#[doc(hidden)]
+pub use std::backtrace::Backtrace;
diff --git a/subprojects/thiserror/src/provide.rs b/subprojects/thiserror/src/provide.rs
new file mode 100644
index 0000000..4b2f06a
--- /dev/null
+++ b/subprojects/thiserror/src/provide.rs
@@ -0,0 +1,20 @@
+use core::error::{Error, Request};
+
+#[doc(hidden)]
+pub trait ThiserrorProvide: Sealed {
+    fn thiserror_provide<'a>(&'a self, request: &mut Request<'a>);
+}
+
+impl<T> ThiserrorProvide for T
+where
+    T: Error + ?Sized,
+{
+    #[inline]
+    fn thiserror_provide<'a>(&'a self, request: &mut Request<'a>) {
+        self.provide(request);
+    }
+}
+
+#[doc(hidden)]
+pub trait Sealed {}
+impl<T: Error + ?Sized> Sealed for T {}
diff --git a/subprojects/thiserror/src/var.rs b/subprojects/thiserror/src/var.rs
new file mode 100644
index 0000000..ecfcd85
--- /dev/null
+++ b/subprojects/thiserror/src/var.rs
@@ -0,0 +1,9 @@
+use core::fmt::{self, Pointer};
+
+pub struct Var<'a, T: ?Sized>(pub &'a T);
+
+impl<'a, T: Pointer + ?Sized> Pointer for Var<'a, T> {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        Pointer::fmt(self.0, formatter)
+    }
+}
diff --git a/subprojects/thiserror/tests/compiletest.rs b/subprojects/thiserror/tests/compiletest.rs
new file mode 100644
index 0000000..23a6a06
--- /dev/null
+++ b/subprojects/thiserror/tests/compiletest.rs
@@ -0,0 +1,7 @@
+#[rustversion::attr(not(nightly), ignore = "requires nightly")]
+#[cfg_attr(miri, ignore = "incompatible with miri")]
+#[test]
+fn ui() {
+    let t = trybuild::TestCases::new();
+    t.compile_fail("tests/ui/*.rs");
+}
diff --git a/subprojects/thiserror/tests/no-std/Cargo.toml b/subprojects/thiserror/tests/no-std/Cargo.toml
new file mode 100644
index 0000000..8b03d2f
--- /dev/null
+++ b/subprojects/thiserror/tests/no-std/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "thiserror_no_std_test"
+version = "0.0.0"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+edition = "2021"
+publish = false
+
+[lib]
+path = "test.rs"
+
+[dependencies]
+thiserror = { path = "../..", default-features = false }
diff --git a/subprojects/thiserror/tests/no-std/test.rs b/subprojects/thiserror/tests/no-std/test.rs
new file mode 100644
index 0000000..da7899c
--- /dev/null
+++ b/subprojects/thiserror/tests/no-std/test.rs
@@ -0,0 +1,58 @@
+#![no_std]
+
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error("Error::E")]
+    E(#[from] SourceError),
+}
+
+#[derive(Error, Debug)]
+#[error("SourceError {field}")]
+pub struct SourceError {
+    pub field: i32,
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{Error, SourceError};
+    use core::error::Error as _;
+    use core::fmt::{self, Write};
+    use core::mem;
+
+    struct Buf<'a>(&'a mut [u8]);
+
+    impl Write for Buf<'_> {
+        fn write_str(&mut self, s: &str) -> fmt::Result {
+            if s.len() <= self.0.len() {
+                let (out, rest) = mem::take(&mut self.0).split_at_mut(s.len());
+                out.copy_from_slice(s.as_bytes());
+                self.0 = rest;
+                Ok(())
+            } else {
+                Err(fmt::Error)
+            }
+        }
+    }
+
+    #[test]
+    fn test() {
+        let source = SourceError { field: -1 };
+        let error = Error::from(source);
+
+        let source = error
+            .source()
+            .unwrap()
+            .downcast_ref::<SourceError>()
+            .unwrap();
+
+        let mut msg = [b'~'; 17];
+        write!(Buf(&mut msg), "{error}").unwrap();
+        assert_eq!(msg, *b"Error::E~~~~~~~~~");
+
+        let mut msg = [b'~'; 17];
+        write!(Buf(&mut msg), "{source}").unwrap();
+        assert_eq!(msg, *b"SourceError -1~~~");
+    }
+}
diff --git a/subprojects/thiserror/tests/test_backtrace.rs b/subprojects/thiserror/tests/test_backtrace.rs
new file mode 100644
index 0000000..cc25676
--- /dev/null
+++ b/subprojects/thiserror/tests/test_backtrace.rs
@@ -0,0 +1,289 @@
+#![cfg(feature = "std")]
+#![cfg_attr(thiserror_nightly_testing, feature(error_generic_member_access))]
+
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct Inner;
+
+#[cfg(thiserror_nightly_testing)]
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct InnerBacktrace {
+    backtrace: std::backtrace::Backtrace,
+}
+
+#[cfg(thiserror_nightly_testing)]
+pub mod structs {
+    use super::{Inner, InnerBacktrace};
+    use std::backtrace::Backtrace;
+    use std::error::{self, Error};
+    use std::sync::Arc;
+    use thiserror::Error;
+
+    mod not_backtrace {
+        #[derive(Debug)]
+        pub struct Backtrace;
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct PlainBacktrace {
+        backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct ExplicitBacktrace {
+        #[backtrace]
+        backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct NotBacktrace {
+        backtrace: crate::structs::not_backtrace::r#Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptBacktrace {
+        #[backtrace]
+        backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct ArcBacktrace {
+        #[backtrace]
+        backtrace: Arc<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct BacktraceFrom {
+        #[from]
+        source: Inner,
+        #[backtrace]
+        backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct CombinedBacktraceFrom {
+        #[from]
+        #[backtrace]
+        source: InnerBacktrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptBacktraceFrom {
+        #[from]
+        source: Inner,
+        #[backtrace]
+        backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct ArcBacktraceFrom {
+        #[from]
+        source: Inner,
+        #[backtrace]
+        backtrace: Arc<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct AnyhowBacktrace {
+        #[backtrace]
+        source: anyhow::Error,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct BoxDynErrorBacktrace {
+        #[backtrace]
+        source: Box<dyn Error>,
+    }
+
+    #[test]
+    fn test_backtrace() {
+        let error = PlainBacktrace {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ExplicitBacktrace {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktrace {
+            backtrace: Some(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktrace {
+            backtrace: Arc::new(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = BacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = CombinedBacktraceFrom::from(InnerBacktrace {
+            backtrace: Backtrace::capture(),
+        });
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = AnyhowBacktrace {
+            source: anyhow::Error::msg("..."),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = BoxDynErrorBacktrace {
+            source: Box::new(PlainBacktrace {
+                backtrace: Backtrace::capture(),
+            }),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+    }
+}
+
+#[cfg(thiserror_nightly_testing)]
+pub mod enums {
+    use super::{Inner, InnerBacktrace};
+    use std::backtrace::Backtrace;
+    use std::error;
+    use std::sync::Arc;
+    use thiserror::Error;
+
+    #[derive(Error, Debug)]
+    pub enum PlainBacktrace {
+        #[error("...")]
+        Test { backtrace: Backtrace },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum ExplicitBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Backtrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum ArcBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Arc<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum BacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            source: Inner,
+            #[backtrace]
+            backtrace: Backtrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum CombinedBacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            #[backtrace]
+            source: InnerBacktrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptBacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            source: Inner,
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum ArcBacktraceFrom {
+        #[error("...")]
+        Test {
+            #[from]
+            source: Inner,
+            #[backtrace]
+            backtrace: Arc<Backtrace>,
+        },
+    }
+
+    #[test]
+    fn test_backtrace() {
+        let error = PlainBacktrace::Test {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ExplicitBacktrace::Test {
+            backtrace: Backtrace::capture(),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktrace::Test {
+            backtrace: Some(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktrace::Test {
+            backtrace: Arc::new(Backtrace::capture()),
+        };
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = BacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = CombinedBacktraceFrom::from(InnerBacktrace {
+            backtrace: Backtrace::capture(),
+        });
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = OptBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+
+        let error = ArcBacktraceFrom::from(Inner);
+        assert!(error::request_ref::<Backtrace>(&error).is_some());
+    }
+}
+
+#[test]
+#[cfg_attr(
+    not(thiserror_nightly_testing),
+    ignore = "requires `--cfg=thiserror_nightly_testing`"
+)]
+fn test_backtrace() {}
diff --git a/subprojects/thiserror/tests/test_display.rs b/subprojects/thiserror/tests/test_display.rs
new file mode 100644
index 0000000..cace226
--- /dev/null
+++ b/subprojects/thiserror/tests/test_display.rs
@@ -0,0 +1,478 @@
+#![allow(
+    clippy::elidable_lifetime_names,
+    clippy::needless_lifetimes,
+    clippy::needless_raw_string_hashes,
+    clippy::trivially_copy_pass_by_ref,
+    clippy::uninlined_format_args
+)]
+
+use core::fmt::{self, Display};
+use thiserror::Error;
+
+fn assert<T: Display>(expected: &str, value: T) {
+    assert_eq!(expected, value.to_string());
+}
+
+#[test]
+fn test_braced() {
+    #[derive(Error, Debug)]
+    #[error("braced error: {msg}")]
+    struct Error {
+        msg: String,
+    }
+
+    let msg = "T".to_owned();
+    assert("braced error: T", Error { msg });
+}
+
+#[test]
+fn test_braced_unused() {
+    #[derive(Error, Debug)]
+    #[error("braced error")]
+    struct Error {
+        extra: usize,
+    }
+
+    assert("braced error", Error { extra: 0 });
+}
+
+#[test]
+fn test_tuple() {
+    #[derive(Error, Debug)]
+    #[error("tuple error: {0}")]
+    struct Error(usize);
+
+    assert("tuple error: 0", Error(0));
+}
+
+#[test]
+fn test_unit() {
+    #[derive(Error, Debug)]
+    #[error("unit error")]
+    struct Error;
+
+    assert("unit error", Error);
+}
+
+#[test]
+fn test_enum() {
+    #[derive(Error, Debug)]
+    enum Error {
+        #[error("braced error: {id}")]
+        Braced { id: usize },
+        #[error("tuple error: {0}")]
+        Tuple(usize),
+        #[error("unit error")]
+        Unit,
+    }
+
+    assert("braced error: 0", Error::Braced { id: 0 });
+    assert("tuple error: 0", Error::Tuple(0));
+    assert("unit error", Error::Unit);
+}
+
+#[test]
+fn test_constants() {
+    #[derive(Error, Debug)]
+    #[error("{MSG}: {id:?} (code {CODE:?})")]
+    struct Error {
+        id: &'static str,
+    }
+
+    const MSG: &str = "failed to do";
+    const CODE: usize = 9;
+
+    assert("failed to do: \"\" (code 9)", Error { id: "" });
+}
+
+#[test]
+fn test_inherit() {
+    #[derive(Error, Debug)]
+    #[error("{0}")]
+    enum Error {
+        Some(&'static str),
+        #[error("other error")]
+        Other(&'static str),
+    }
+
+    assert("some error", Error::Some("some error"));
+    assert("other error", Error::Other("..."));
+}
+
+#[test]
+fn test_brace_escape() {
+    #[derive(Error, Debug)]
+    #[error("fn main() {{}}")]
+    struct Error;
+
+    assert("fn main() {}", Error);
+}
+
+#[test]
+fn test_expr() {
+    #[derive(Error, Debug)]
+    #[error("1 + 1 = {}", 1 + 1)]
+    struct Error;
+    assert("1 + 1 = 2", Error);
+}
+
+#[test]
+fn test_nested() {
+    #[derive(Error, Debug)]
+    #[error("!bool = {}", not(.0))]
+    struct Error(bool);
+
+    #[allow(clippy::trivially_copy_pass_by_ref)]
+    fn not(bool: &bool) -> bool {
+        !*bool
+    }
+
+    assert("!bool = false", Error(true));
+}
+
+#[test]
+fn test_match() {
+    #[derive(Error, Debug)]
+    #[error("{intro}: {0}", intro = match .1 {
+        Some(n) => format!("error occurred with {}", n),
+        None => "there was an empty error".to_owned(),
+    })]
+    struct Error(String, Option<usize>);
+
+    assert(
+        "error occurred with 1: ...",
+        Error("...".to_owned(), Some(1)),
+    );
+    assert(
+        "there was an empty error: ...",
+        Error("...".to_owned(), None),
+    );
+}
+
+#[test]
+fn test_nested_display() {
+    // Same behavior as the one in `test_match`, but without String allocations.
+    #[derive(Error, Debug)]
+    #[error("{}", {
+        struct Msg<'a>(&'a String, &'a Option<usize>);
+        impl<'a> Display for Msg<'a> {
+            fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                match self.1 {
+                    Some(n) => write!(formatter, "error occurred with {}", n),
+                    None => write!(formatter, "there was an empty error"),
+                }?;
+                write!(formatter, ": {}", self.0)
+            }
+        }
+        Msg(.0, .1)
+    })]
+    struct Error(String, Option<usize>);
+
+    assert(
+        "error occurred with 1: ...",
+        Error("...".to_owned(), Some(1)),
+    );
+    assert(
+        "there was an empty error: ...",
+        Error("...".to_owned(), None),
+    );
+}
+
+#[test]
+fn test_void() {
+    #[allow(clippy::empty_enums)]
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub enum Error {}
+
+    let _: Error;
+}
+
+#[test]
+fn test_mixed() {
+    #[derive(Error, Debug)]
+    #[error("a={a} :: b={} :: c={c} :: d={d}", 1, c = 2, d = 3)]
+    struct Error {
+        a: usize,
+        d: usize,
+    }
+
+    assert("a=0 :: b=1 :: c=2 :: d=3", Error { a: 0, d: 0 });
+}
+
+#[test]
+fn test_ints() {
+    #[derive(Error, Debug)]
+    enum Error {
+        #[error("error {0}")]
+        Tuple(usize, usize),
+        #[error("error {0}", '?')]
+        Struct { v: usize },
+    }
+
+    assert("error 9", Error::Tuple(9, 0));
+    assert("error ?", Error::Struct { v: 0 });
+}
+
+#[test]
+fn test_trailing_comma() {
+    #[derive(Error, Debug)]
+    #[error(
+        "error {0}",
+    )]
+    #[rustfmt::skip]
+    struct Error(char);
+
+    assert("error ?", Error('?'));
+}
+
+#[test]
+fn test_field() {
+    #[derive(Debug)]
+    struct Inner {
+        data: usize,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("{}", .0.data)]
+    struct Error(Inner);
+
+    assert("0", Error(Inner { data: 0 }));
+}
+
+#[test]
+fn test_nested_tuple_field() {
+    #[derive(Debug)]
+    struct Inner(usize);
+
+    #[derive(Error, Debug)]
+    #[error("{}", .0.0)]
+    struct Error(Inner);
+
+    assert("0", Error(Inner(0)));
+}
+
+#[test]
+fn test_pointer() {
+    #[derive(Error, Debug)]
+    #[error("{field:p}")]
+    pub struct Struct {
+        field: Box<i32>,
+    }
+
+    let s = Struct {
+        field: Box::new(-1),
+    };
+    assert_eq!(s.to_string(), format!("{:p}", s.field));
+}
+
+#[test]
+fn test_macro_rules_variant_from_call_site() {
+    // Regression test for https://github.com/dtolnay/thiserror/issues/86
+
+    macro_rules! decl_error {
+        ($variant:ident($value:ident)) => {
+            #[derive(Error, Debug)]
+            pub enum Error0 {
+                #[error("{0:?}")]
+                $variant($value),
+            }
+
+            #[derive(Error, Debug)]
+            #[error("{0:?}")]
+            pub enum Error1 {
+                $variant($value),
+            }
+        };
+    }
+
+    decl_error!(Repro(u8));
+
+    assert("0", Error0::Repro(0));
+    assert("0", Error1::Repro(0));
+}
+
+#[test]
+fn test_macro_rules_message_from_call_site() {
+    // Regression test for https://github.com/dtolnay/thiserror/issues/398
+
+    macro_rules! decl_error {
+        ($($errors:tt)*) => {
+            #[derive(Error, Debug)]
+            pub enum Error {
+                $($errors)*
+            }
+        };
+    }
+
+    decl_error! {
+        #[error("{0}")]
+        Unnamed(u8),
+        #[error("{x}")]
+        Named { x: u8 },
+    }
+
+    assert("0", Error::Unnamed(0));
+    assert("0", Error::Named { x: 0 });
+}
+
+#[test]
+fn test_raw() {
+    #[derive(Error, Debug)]
+    #[error("braced raw error: {fn}")]
+    struct Error {
+        r#fn: &'static str,
+    }
+
+    assert("braced raw error: T", Error { r#fn: "T" });
+}
+
+#[test]
+fn test_raw_enum() {
+    #[derive(Error, Debug)]
+    enum Error {
+        #[error("braced raw error: {fn}")]
+        Braced { r#fn: &'static str },
+    }
+
+    assert("braced raw error: T", Error::Braced { r#fn: "T" });
+}
+
+#[test]
+fn test_keyword() {
+    #[derive(Error, Debug)]
+    #[error("error: {type}", type = 1)]
+    struct Error;
+
+    assert("error: 1", Error);
+}
+
+#[test]
+fn test_self() {
+    #[derive(Error, Debug)]
+    #[error("error: {self:?}")]
+    struct Error;
+
+    assert("error: Error", Error);
+}
+
+#[test]
+fn test_str_special_chars() {
+    #[derive(Error, Debug)]
+    pub enum Error {
+        #[error("brace left {{")]
+        BraceLeft,
+        #[error("brace left 2 \x7B\x7B")]
+        BraceLeft2,
+        #[error("brace left 3 \u{7B}\u{7B}")]
+        BraceLeft3,
+        #[error("brace right }}")]
+        BraceRight,
+        #[error("brace right 2 \x7D\x7D")]
+        BraceRight2,
+        #[error("brace right 3 \u{7D}\u{7D}")]
+        BraceRight3,
+        #[error(
+            "new_\
+line"
+        )]
+        NewLine,
+        #[error("escape24 \u{78}")]
+        Escape24,
+    }
+
+    assert("brace left {", Error::BraceLeft);
+    assert("brace left 2 {", Error::BraceLeft2);
+    assert("brace left 3 {", Error::BraceLeft3);
+    assert("brace right }", Error::BraceRight);
+    assert("brace right 2 }", Error::BraceRight2);
+    assert("brace right 3 }", Error::BraceRight3);
+    assert("new_line", Error::NewLine);
+    assert("escape24 x", Error::Escape24);
+}
+
+#[test]
+fn test_raw_str() {
+    #[derive(Error, Debug)]
+    pub enum Error {
+        #[error(r#"raw brace left {{"#)]
+        BraceLeft,
+        #[error(r#"raw brace left 2 \x7B"#)]
+        BraceLeft2,
+        #[error(r#"raw brace right }}"#)]
+        BraceRight,
+        #[error(r#"raw brace right 2 \x7D"#)]
+        BraceRight2,
+    }
+
+    assert(r#"raw brace left {"#, Error::BraceLeft);
+    assert(r#"raw brace left 2 \x7B"#, Error::BraceLeft2);
+    assert(r#"raw brace right }"#, Error::BraceRight);
+    assert(r#"raw brace right 2 \x7D"#, Error::BraceRight2);
+}
+
+mod util {
+    use core::fmt::{self, Octal};
+
+    pub fn octal<T: Octal>(value: &T, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "0o{:o}", value)
+    }
+}
+
+#[test]
+fn test_fmt_path() {
+    fn unit(formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("unit=")
+    }
+
+    fn pair(k: &i32, v: &i32, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "pair={k}:{v}")
+    }
+
+    #[derive(Error, Debug)]
+    pub enum Error {
+        #[error(fmt = unit)]
+        Unit,
+        #[error(fmt = pair)]
+        Tuple(i32, i32),
+        #[error(fmt = pair)]
+        Entry { k: i32, v: i32 },
+        #[error(fmt = crate::util::octal)]
+        I16(i16),
+        #[error(fmt = crate::util::octal::<i32>)]
+        I32 { n: i32 },
+        #[error(fmt = core::fmt::Octal::fmt)]
+        I64(i64),
+        #[error("...{0}")]
+        Other(bool),
+    }
+
+    assert("unit=", Error::Unit);
+    assert("pair=10:0", Error::Tuple(10, 0));
+    assert("pair=10:0", Error::Entry { k: 10, v: 0 });
+    assert("0o777", Error::I16(0o777));
+    assert("0o777", Error::I32 { n: 0o777 });
+    assert("777", Error::I64(0o777));
+    assert("...false", Error::Other(false));
+}
+
+#[test]
+fn test_fmt_path_inherited() {
+    #[derive(Error, Debug)]
+    #[error(fmt = crate::util::octal)]
+    pub enum Error {
+        I16(i16),
+        I32 {
+            n: i32,
+        },
+        #[error(fmt = core::fmt::Octal::fmt)]
+        I64(i64),
+        #[error("...{0}")]
+        Other(bool),
+    }
+
+    assert("0o777", Error::I16(0o777));
+    assert("0o777", Error::I32 { n: 0o777 });
+    assert("777", Error::I64(0o777));
+    assert("...false", Error::Other(false));
+}
diff --git a/subprojects/thiserror/tests/test_error.rs b/subprojects/thiserror/tests/test_error.rs
new file mode 100644
index 0000000..eb52cef
--- /dev/null
+++ b/subprojects/thiserror/tests/test_error.rs
@@ -0,0 +1,56 @@
+#![allow(dead_code)]
+
+use core::fmt::{self, Display};
+use std::io;
+use thiserror::Error;
+
+macro_rules! unimplemented_display {
+    ($ty:ty) => {
+        impl Display for $ty {
+            fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+                unimplemented!()
+            }
+        }
+    };
+}
+
+#[derive(Error, Debug)]
+struct BracedError {
+    msg: String,
+    pos: usize,
+}
+
+#[derive(Error, Debug)]
+struct TupleError(String, usize);
+
+#[derive(Error, Debug)]
+struct UnitError;
+
+#[derive(Error, Debug)]
+struct WithSource {
+    #[source]
+    cause: io::Error,
+}
+
+#[derive(Error, Debug)]
+struct WithAnyhow {
+    #[source]
+    cause: anyhow::Error,
+}
+
+#[derive(Error, Debug)]
+enum EnumError {
+    Braced {
+        #[source]
+        cause: io::Error,
+    },
+    Tuple(#[source] io::Error),
+    Unit,
+}
+
+unimplemented_display!(BracedError);
+unimplemented_display!(TupleError);
+unimplemented_display!(UnitError);
+unimplemented_display!(WithSource);
+unimplemented_display!(WithAnyhow);
+unimplemented_display!(EnumError);
diff --git a/subprojects/thiserror/tests/test_expr.rs b/subprojects/thiserror/tests/test_expr.rs
new file mode 100644
index 0000000..1872fb5
--- /dev/null
+++ b/subprojects/thiserror/tests/test_expr.rs
@@ -0,0 +1,118 @@
+#![allow(clippy::iter_cloned_collect, clippy::uninlined_format_args)]
+
+use core::fmt::Display;
+#[cfg(feature = "std")]
+use std::path::PathBuf;
+use thiserror::Error;
+
+// Some of the elaborate cases from the rcc codebase, which is a C compiler in
+// Rust. https://github.com/jyn514/rcc/blob/0.8.0/src/data/error.rs
+#[derive(Error, Debug)]
+pub enum CompilerError {
+    #[error("cannot shift {} by {maximum} or more bits (got {current})", if *.is_left { "left" } else { "right" })]
+    TooManyShiftBits {
+        is_left: bool,
+        maximum: u64,
+        current: u64,
+    },
+
+    #[error("#error {}", (.0).iter().copied().collect::<Vec<_>>().join(" "))]
+    User(Vec<&'static str>),
+
+    #[error("overflow while parsing {}integer literal",
+        if let Some(signed) = .is_signed {
+            if *signed { "signed "} else { "unsigned "}
+        } else {
+            ""
+        }
+    )]
+    IntegerOverflow { is_signed: Option<bool> },
+
+    #[error("overflow while parsing {}integer literal", match .is_signed {
+        Some(true) => "signed ",
+        Some(false) => "unsigned ",
+        None => "",
+    })]
+    IntegerOverflow2 { is_signed: Option<bool> },
+}
+
+// Examples drawn from Rustup.
+#[derive(Error, Debug)]
+pub enum RustupError {
+    #[error(
+        "toolchain '{name}' does not contain component {component}{}",
+        .suggestion
+            .as_ref()
+            .map_or_else(String::new, |s| format!("; did you mean '{}'?", s)),
+    )]
+    UnknownComponent {
+        name: String,
+        component: String,
+        suggestion: Option<String>,
+    },
+}
+
+#[track_caller]
+fn assert<T: Display>(expected: &str, value: T) {
+    assert_eq!(expected, value.to_string());
+}
+
+#[test]
+fn test_rcc() {
+    assert(
+        "cannot shift left by 32 or more bits (got 50)",
+        CompilerError::TooManyShiftBits {
+            is_left: true,
+            maximum: 32,
+            current: 50,
+        },
+    );
+
+    assert("#error A B C", CompilerError::User(vec!["A", "B", "C"]));
+
+    assert(
+        "overflow while parsing signed integer literal",
+        CompilerError::IntegerOverflow {
+            is_signed: Some(true),
+        },
+    );
+}
+
+#[test]
+fn test_rustup() {
+    assert(
+        "toolchain 'nightly' does not contain component clipy; did you mean 'clippy'?",
+        RustupError::UnknownComponent {
+            name: "nightly".to_owned(),
+            component: "clipy".to_owned(),
+            suggestion: Some("clippy".to_owned()),
+        },
+    );
+}
+
+// Regression test for https://github.com/dtolnay/thiserror/issues/335
+#[cfg(feature = "std")]
+#[test]
+#[allow(non_snake_case)]
+fn test_assoc_type_equality_constraint() {
+    pub trait Trait<T>: Display {
+        type A;
+    }
+
+    impl<T> Trait<T> for i32 {
+        type A = i32;
+    }
+
+    #[derive(Error, Debug)]
+    #[error("{A} {b}", b = &0 as &dyn Trait<i32, A = i32>)]
+    pub struct Error {
+        pub A: PathBuf,
+    }
+
+    assert(
+        "... 0",
+        Error {
+            A: PathBuf::from("..."),
+        },
+    );
+}
diff --git a/subprojects/thiserror/tests/test_from.rs b/subprojects/thiserror/tests/test_from.rs
new file mode 100644
index 0000000..51af40b
--- /dev/null
+++ b/subprojects/thiserror/tests/test_from.rs
@@ -0,0 +1,64 @@
+#![allow(clippy::extra_unused_type_parameters)]
+
+use std::io;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct ErrorStruct {
+    #[from]
+    source: io::Error,
+}
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct ErrorStructOptional {
+    #[from]
+    source: Option<io::Error>,
+}
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct ErrorTuple(#[from] io::Error);
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct ErrorTupleOptional(#[from] Option<io::Error>);
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub enum ErrorEnum {
+    Test {
+        #[from]
+        source: io::Error,
+    },
+}
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub enum ErrorEnumOptional {
+    Test {
+        #[from]
+        source: Option<io::Error>,
+    },
+}
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub enum Many {
+    Any(#[from] anyhow::Error),
+    Io(#[from] io::Error),
+}
+
+fn assert_impl<T: From<io::Error>>() {}
+
+#[test]
+fn test_from() {
+    assert_impl::<ErrorStruct>();
+    assert_impl::<ErrorStructOptional>();
+    assert_impl::<ErrorTuple>();
+    assert_impl::<ErrorTupleOptional>();
+    assert_impl::<ErrorEnum>();
+    assert_impl::<ErrorEnumOptional>();
+    assert_impl::<Many>();
+}
diff --git a/subprojects/thiserror/tests/test_generics.rs b/subprojects/thiserror/tests/test_generics.rs
new file mode 100644
index 0000000..bcbfee0
--- /dev/null
+++ b/subprojects/thiserror/tests/test_generics.rs
@@ -0,0 +1,205 @@
+#![allow(clippy::needless_late_init, clippy::uninlined_format_args)]
+
+use core::fmt::{self, Debug, Display};
+use core::str::FromStr;
+use thiserror::Error;
+
+pub struct NoFormat;
+
+#[derive(Debug)]
+pub struct DebugOnly;
+
+pub struct DisplayOnly;
+
+impl Display for DisplayOnly {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("display only")
+    }
+}
+
+#[derive(Debug)]
+pub struct DebugAndDisplay;
+
+impl Display for DebugAndDisplay {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("debug and display")
+    }
+}
+
+// Should expand to:
+//
+//     impl<E> Display for EnumDebugField<E>
+//     where
+//         E: Debug;
+//
+//     impl<E> Error for EnumDebugField<E>
+//     where
+//         Self: Debug + Display;
+//
+#[derive(Error, Debug)]
+pub enum EnumDebugGeneric<E> {
+    #[error("{0:?}")]
+    FatalError(E),
+}
+
+// Should expand to:
+//
+//     impl<E> Display for EnumFromGeneric<E>;
+//
+//     impl<E> Error for EnumFromGeneric<E>
+//     where
+//         EnumDebugGeneric<E>: Error + 'static,
+//         Self: Debug + Display;
+//
+#[derive(Error, Debug)]
+pub enum EnumFromGeneric<E> {
+    #[error("enum from generic")]
+    Source(#[from] EnumDebugGeneric<E>),
+}
+
+// Should expand to:
+//
+//     impl<HasDisplay, HasDebug, HasNeither> Display
+//         for EnumCompound<HasDisplay, HasDebug, HasNeither>
+//     where
+//         HasDisplay: Display,
+//         HasDebug: Debug;
+//
+//     impl<HasDisplay, HasDebug, HasNeither> Error
+//         for EnumCompound<HasDisplay, HasDebug, HasNeither>
+//     where
+//         Self: Debug + Display;
+//
+#[derive(Error)]
+pub enum EnumCompound<HasDisplay, HasDebug, HasNeither> {
+    #[error("{0} {1:?}")]
+    DisplayDebug(HasDisplay, HasDebug),
+    #[error("{0}")]
+    Display(HasDisplay, HasNeither),
+    #[error("{1:?}")]
+    Debug(HasNeither, HasDebug),
+}
+
+impl<HasDisplay, HasDebug, HasNeither> Debug for EnumCompound<HasDisplay, HasDebug, HasNeither> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("EnumCompound")
+    }
+}
+
+#[test]
+fn test_display_enum_compound() {
+    let mut instance: EnumCompound<DisplayOnly, DebugOnly, NoFormat>;
+
+    instance = EnumCompound::DisplayDebug(DisplayOnly, DebugOnly);
+    assert_eq!(format!("{}", instance), "display only DebugOnly");
+
+    instance = EnumCompound::Display(DisplayOnly, NoFormat);
+    assert_eq!(format!("{}", instance), "display only");
+
+    instance = EnumCompound::Debug(NoFormat, DebugOnly);
+    assert_eq!(format!("{}", instance), "DebugOnly");
+}
+
+// Should expand to:
+//
+//     impl<E> Display for EnumTransparentGeneric<E>
+//     where
+//         E: Display;
+//
+//     impl<E> Error for EnumTransparentGeneric<E>
+//     where
+//         E: Error,
+//         Self: Debug + Display;
+//
+#[derive(Error, Debug)]
+pub enum EnumTransparentGeneric<E> {
+    #[error(transparent)]
+    Other(E),
+}
+
+// Should expand to:
+//
+//     impl<E> Display for StructDebugGeneric<E>
+//     where
+//         E: Debug;
+//
+//     impl<E> Error for StructDebugGeneric<E>
+//     where
+//         Self: Debug + Display;
+//
+#[derive(Error, Debug)]
+#[error("{underlying:?}")]
+pub struct StructDebugGeneric<E> {
+    pub underlying: E,
+}
+
+// Should expand to:
+//
+//     impl<E> Error for StructFromGeneric<E>
+//     where
+//         StructDebugGeneric<E>: Error + 'static,
+//         Self: Debug + Display;
+//
+#[derive(Error, Debug)]
+pub struct StructFromGeneric<E> {
+    #[from]
+    pub source: StructDebugGeneric<E>,
+}
+
+// Should expand to:
+//
+//     impl<E> Display for StructTransparentGeneric<E>
+//     where
+//         E: Display;
+//
+//     impl<E> Error for StructTransparentGeneric<E>
+//     where
+//         E: Error,
+//         Self: Debug + Display;
+//
+#[derive(Error, Debug)]
+#[error(transparent)]
+pub struct StructTransparentGeneric<E>(pub E);
+
+// Should expand to:
+//
+//     impl<T: FromStr> Display for AssociatedTypeError<T>
+//     where
+//         T::Err: Display;
+//
+//     impl<T: FromStr> Error for AssociatedTypeError<T>
+//     where
+//         Self: Debug + Display;
+//
+#[derive(Error, Debug)]
+pub enum AssociatedTypeError<T: FromStr> {
+    #[error("couldn't parse matrix")]
+    Other,
+    #[error("couldn't parse entry: {0}")]
+    EntryParseError(T::Err),
+}
+
+// Regression test for https://github.com/dtolnay/thiserror/issues/345
+#[test]
+fn test_no_bound_on_named_fmt() {
+    #[derive(Error, Debug)]
+    #[error("{thing}", thing = "...")]
+    struct Error<T> {
+        thing: T,
+    }
+
+    let error = Error { thing: DebugOnly };
+    assert_eq!(error.to_string(), "...");
+}
+
+#[test]
+fn test_multiple_bound() {
+    #[derive(Error, Debug)]
+    #[error("0x{thing:x} 0x{thing:X}")]
+    pub struct Error<T> {
+        thing: T,
+    }
+
+    let error = Error { thing: 0xFFi32 };
+    assert_eq!(error.to_string(), "0xff 0xFF");
+}
diff --git a/subprojects/thiserror/tests/test_lints.rs b/subprojects/thiserror/tests/test_lints.rs
new file mode 100644
index 0000000..802ad50
--- /dev/null
+++ b/subprojects/thiserror/tests/test_lints.rs
@@ -0,0 +1,98 @@
+#![allow(clippy::mixed_attributes_style)]
+
+use thiserror::Error;
+
+pub use std::error::Error;
+
+#[test]
+fn test_allow_attributes() {
+    #![deny(clippy::allow_attributes)]
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct MyError(#[from] anyhow::Error);
+
+    let _: MyError;
+}
+
+#[test]
+fn test_unused_qualifications() {
+    #![deny(unused_qualifications)]
+
+    // Expansion of derive(Error) macro can't know whether something like
+    // std::error::Error is already imported in the caller's scope so it must
+    // suppress unused_qualifications.
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct MyError;
+
+    let _: MyError;
+}
+
+#[test]
+fn test_needless_lifetimes() {
+    #![allow(dead_code)]
+    #![deny(clippy::elidable_lifetime_names, clippy::needless_lifetimes)]
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub enum MyError<'a> {
+        A(#[from] std::io::Error),
+        B(&'a ()),
+    }
+
+    let _: MyError;
+}
+
+#[test]
+fn test_deprecated() {
+    #![deny(deprecated)]
+
+    #[derive(Error, Debug)]
+    #[deprecated]
+    #[error("...")]
+    pub struct DeprecatedStruct;
+
+    #[derive(Error, Debug)]
+    #[error("{message} {}", .message)]
+    pub struct DeprecatedStructField {
+        #[deprecated]
+        message: String,
+    }
+
+    #[derive(Error, Debug)]
+    #[deprecated]
+    pub enum DeprecatedEnum {
+        #[error("...")]
+        Variant,
+    }
+
+    #[derive(Error, Debug)]
+    pub enum DeprecatedVariant {
+        #[deprecated]
+        #[error("...")]
+        Variant,
+    }
+
+    #[derive(Error, Debug)]
+    pub enum DeprecatedFrom {
+        #[error(transparent)]
+        Variant(
+            #[from]
+            #[allow(deprecated)]
+            DeprecatedStruct,
+        ),
+    }
+
+    #[allow(deprecated)]
+    let _: DeprecatedStruct;
+    #[allow(deprecated)]
+    let _: DeprecatedStructField;
+    #[allow(deprecated)]
+    let _ = DeprecatedEnum::Variant;
+    #[allow(deprecated)]
+    let _ = DeprecatedVariant::Variant;
+    #[allow(deprecated)]
+    let _ = DeprecatedFrom::Variant(DeprecatedStruct);
+}
diff --git a/subprojects/thiserror/tests/test_option.rs b/subprojects/thiserror/tests/test_option.rs
new file mode 100644
index 0000000..21cd5e1
--- /dev/null
+++ b/subprojects/thiserror/tests/test_option.rs
@@ -0,0 +1,109 @@
+#![cfg(feature = "std")]
+#![cfg_attr(thiserror_nightly_testing, feature(error_generic_member_access))]
+
+#[cfg(thiserror_nightly_testing)]
+pub mod structs {
+    use std::backtrace::Backtrace;
+    use thiserror::Error;
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptSourceNoBacktrace {
+        #[source]
+        pub source: Option<anyhow::Error>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptSourceAlwaysBacktrace {
+        #[source]
+        pub source: Option<anyhow::Error>,
+        pub backtrace: Backtrace,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct NoSourceOptBacktrace {
+        #[backtrace]
+        pub backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct AlwaysSourceOptBacktrace {
+        pub source: anyhow::Error,
+        #[backtrace]
+        pub backtrace: Option<Backtrace>,
+    }
+
+    #[derive(Error, Debug)]
+    #[error("...")]
+    pub struct OptSourceOptBacktrace {
+        #[source]
+        pub source: Option<anyhow::Error>,
+        #[backtrace]
+        pub backtrace: Option<Backtrace>,
+    }
+}
+
+#[cfg(thiserror_nightly_testing)]
+pub mod enums {
+    use std::backtrace::Backtrace;
+    use thiserror::Error;
+
+    #[derive(Error, Debug)]
+    pub enum OptSourceNoBacktrace {
+        #[error("...")]
+        Test {
+            #[source]
+            source: Option<anyhow::Error>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptSourceAlwaysBacktrace {
+        #[error("...")]
+        Test {
+            #[source]
+            source: Option<anyhow::Error>,
+            backtrace: Backtrace,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum NoSourceOptBacktrace {
+        #[error("...")]
+        Test {
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum AlwaysSourceOptBacktrace {
+        #[error("...")]
+        Test {
+            source: anyhow::Error,
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+
+    #[derive(Error, Debug)]
+    pub enum OptSourceOptBacktrace {
+        #[error("...")]
+        Test {
+            #[source]
+            source: Option<anyhow::Error>,
+            #[backtrace]
+            backtrace: Option<Backtrace>,
+        },
+    }
+}
+
+#[test]
+#[cfg_attr(
+    not(thiserror_nightly_testing),
+    ignore = "requires `--cfg=thiserror_nightly_testing`"
+)]
+fn test_option() {}
diff --git a/subprojects/thiserror/tests/test_path.rs b/subprojects/thiserror/tests/test_path.rs
new file mode 100644
index 0000000..fa85c1d
--- /dev/null
+++ b/subprojects/thiserror/tests/test_path.rs
@@ -0,0 +1,54 @@
+#![cfg(feature = "std")]
+
+use core::fmt::Display;
+use ref_cast::RefCast;
+use std::path::{Path, PathBuf};
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("failed to read '{file}'")]
+struct StructPathBuf {
+    file: PathBuf,
+}
+
+#[derive(Error, Debug, RefCast)]
+#[repr(C)]
+#[error("failed to read '{file}'")]
+struct StructPath {
+    file: Path,
+}
+
+#[derive(Error, Debug)]
+enum EnumPathBuf {
+    #[error("failed to read '{0}'")]
+    Read(PathBuf),
+}
+
+#[derive(Error, Debug)]
+#[error("{tail}")]
+pub struct UnsizedError {
+    pub head: i32,
+    pub tail: str,
+}
+
+#[derive(Error, Debug)]
+pub enum BothError {
+    #[error("display:{0} debug:{0:?}")]
+    DisplayDebug(PathBuf),
+    #[error("debug:{0:?} display:{0}")]
+    DebugDisplay(PathBuf),
+}
+
+fn assert<T: Display>(expected: &str, value: T) {
+    assert_eq!(expected, value.to_string());
+}
+
+#[test]
+fn test_display() {
+    let path = Path::new("/thiserror");
+    let file = path.to_owned();
+    assert("failed to read '/thiserror'", StructPathBuf { file });
+    let file = path.to_owned();
+    assert("failed to read '/thiserror'", EnumPathBuf::Read(file));
+    assert("failed to read '/thiserror'", StructPath::ref_cast(path));
+}
diff --git a/subprojects/thiserror/tests/test_source.rs b/subprojects/thiserror/tests/test_source.rs
new file mode 100644
index 0000000..29968be
--- /dev/null
+++ b/subprojects/thiserror/tests/test_source.rs
@@ -0,0 +1,82 @@
+use std::error::Error as StdError;
+use std::io;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("implicit source")]
+pub struct ImplicitSource {
+    source: io::Error,
+}
+
+#[derive(Error, Debug)]
+#[error("explicit source")]
+pub struct ExplicitSource {
+    source: String,
+    #[source]
+    io: io::Error,
+}
+
+#[derive(Error, Debug)]
+#[error("boxed source")]
+pub struct BoxedSource {
+    #[source]
+    source: Box<dyn StdError + Send + 'static>,
+}
+
+#[test]
+fn test_implicit_source() {
+    let io = io::Error::new(io::ErrorKind::Other, "oh no!");
+    let error = ImplicitSource { source: io };
+    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+#[test]
+fn test_explicit_source() {
+    let io = io::Error::new(io::ErrorKind::Other, "oh no!");
+    let error = ExplicitSource {
+        source: String::new(),
+        io,
+    };
+    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+#[test]
+fn test_boxed_source() {
+    let source = Box::new(io::Error::new(io::ErrorKind::Other, "oh no!"));
+    let error = BoxedSource { source };
+    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+macro_rules! error_from_macro {
+    ($($variants:tt)*) => {
+        #[derive(Error)]
+        #[derive(Debug)]
+        pub enum MacroSource {
+            $($variants)*
+        }
+    }
+}
+
+// Test that we generate impls with the proper hygiene
+#[rustfmt::skip]
+error_from_macro! {
+    #[error("Something")]
+    Variant(#[from] io::Error)
+}
+
+#[test]
+fn test_not_source() {
+    #[derive(Error, Debug)]
+    #[error("{source} ==> {destination}")]
+    pub struct NotSource {
+        r#source: char,
+        destination: char,
+    }
+
+    let error = NotSource {
+        source: 'S',
+        destination: 'D',
+    };
+    assert_eq!(error.to_string(), "S ==> D");
+    assert!(error.source().is_none());
+}
diff --git a/subprojects/thiserror/tests/test_transparent.rs b/subprojects/thiserror/tests/test_transparent.rs
new file mode 100644
index 0000000..ee30f5b
--- /dev/null
+++ b/subprojects/thiserror/tests/test_transparent.rs
@@ -0,0 +1,96 @@
+use anyhow::anyhow;
+use std::error::Error as _;
+use std::io;
+use thiserror::Error;
+
+#[test]
+fn test_transparent_struct() {
+    #[derive(Error, Debug)]
+    #[error(transparent)]
+    struct Error(ErrorKind);
+
+    #[derive(Error, Debug)]
+    enum ErrorKind {
+        #[error("E0")]
+        E0,
+        #[error("E1")]
+        E1(#[from] io::Error),
+    }
+
+    let error = Error(ErrorKind::E0);
+    assert_eq!("E0", error.to_string());
+    assert!(error.source().is_none());
+
+    let io = io::Error::new(io::ErrorKind::Other, "oh no!");
+    let error = Error(ErrorKind::from(io));
+    assert_eq!("E1", error.to_string());
+    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+#[test]
+fn test_transparent_enum() {
+    #[derive(Error, Debug)]
+    enum Error {
+        #[error("this failed")]
+        This,
+        #[error(transparent)]
+        Other(anyhow::Error),
+    }
+
+    let error = Error::This;
+    assert_eq!("this failed", error.to_string());
+
+    let error = Error::Other(anyhow!("inner").context("outer"));
+    assert_eq!("outer", error.to_string());
+    assert_eq!("inner", error.source().unwrap().to_string());
+}
+
+#[test]
+fn test_transparent_enum_with_default_message() {
+    #[derive(Error, Debug)]
+    #[error("this failed: {0}_{1}")]
+    enum Error {
+        This(i32, i32),
+        #[error(transparent)]
+        Other(anyhow::Error),
+    }
+
+    let error = Error::This(-1, -1);
+    assert_eq!("this failed: -1_-1", error.to_string());
+
+    let error = Error::Other(anyhow!("inner").context("outer"));
+    assert_eq!("outer", error.to_string());
+    assert_eq!("inner", error.source().unwrap().to_string());
+}
+
+#[test]
+fn test_anyhow() {
+    #[derive(Error, Debug)]
+    #[error(transparent)]
+    struct Any(#[from] anyhow::Error);
+
+    let error = Any::from(anyhow!("inner").context("outer"));
+    assert_eq!("outer", error.to_string());
+    assert_eq!("inner", error.source().unwrap().to_string());
+}
+
+#[test]
+fn test_non_static() {
+    #[derive(Error, Debug)]
+    #[error(transparent)]
+    struct Error<'a> {
+        inner: ErrorKind<'a>,
+    }
+
+    #[derive(Error, Debug)]
+    enum ErrorKind<'a> {
+        #[error("unexpected token: {:?}", token)]
+        Unexpected { token: &'a str },
+    }
+
+    let error = Error {
+        inner: ErrorKind::Unexpected { token: "error" },
+    };
+    assert_eq!("unexpected token: \"error\"", error.to_string());
+    assert!(error.source().is_none());
+}
diff --git a/subprojects/thiserror/tests/ui/bad-field-attr.rs b/subprojects/thiserror/tests/ui/bad-field-attr.rs
new file mode 100644
index 0000000..d5429b2
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/bad-field-attr.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(transparent)]
+pub struct Error(#[error(transparent)] std::io::Error);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/bad-field-attr.stderr b/subprojects/thiserror/tests/ui/bad-field-attr.stderr
new file mode 100644
index 0000000..5fb5744
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/bad-field-attr.stderr
@@ -0,0 +1,5 @@
+error: #[error(transparent)] needs to go outside the enum or struct, not on an individual field
+ --> tests/ui/bad-field-attr.rs:5:18
+  |
+5 | pub struct Error(#[error(transparent)] std::io::Error);
+  |                  ^^^^^^^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/concat-display.rs b/subprojects/thiserror/tests/ui/concat-display.rs
new file mode 100644
index 0000000..8b53cc0
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/concat-display.rs
@@ -0,0 +1,15 @@
+use thiserror::Error;
+
+macro_rules! error_type {
+    ($name:ident, $what:expr) => {
+        // Use #[error("invalid {}", $what)] instead.
+
+        #[derive(Error, Debug)]
+        #[error(concat!("invalid ", $what))]
+        pub struct $name;
+    };
+}
+
+error_type!(Error, "foo");
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/concat-display.stderr b/subprojects/thiserror/tests/ui/concat-display.stderr
new file mode 100644
index 0000000..73718ae
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/concat-display.stderr
@@ -0,0 +1,10 @@
+error: expected one of: string literal, `transparent`, `fmt`
+  --> tests/ui/concat-display.rs:8:17
+   |
+ 8 |         #[error(concat!("invalid ", $what))]
+   |                 ^^^^^^
+...
+13 | error_type!(Error, "foo");
+   | ------------------------- in this macro invocation
+   |
+   = note: this error originates in the macro `error_type` (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/subprojects/thiserror/tests/ui/display-underscore.rs b/subprojects/thiserror/tests/ui/display-underscore.rs
new file mode 100644
index 0000000..335614b
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/display-underscore.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("{_}")]
+pub struct Error;
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/display-underscore.stderr b/subprojects/thiserror/tests/ui/display-underscore.stderr
new file mode 100644
index 0000000..36882b9
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/display-underscore.stderr
@@ -0,0 +1,7 @@
+error: invalid format string: invalid argument name `_`
+ --> tests/ui/display-underscore.rs:4:11
+  |
+4 | #[error("{_}")]
+  |           ^ invalid argument name in format string
+  |
+  = note: argument name cannot be a single underscore
diff --git a/subprojects/thiserror/tests/ui/duplicate-enum-source.rs b/subprojects/thiserror/tests/ui/duplicate-enum-source.rs
new file mode 100644
index 0000000..15e579f
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-enum-source.rs
@@ -0,0 +1,13 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum ErrorEnum {
+    Confusing {
+        #[source]
+        a: std::io::Error,
+        #[source]
+        b: anyhow::Error,
+    },
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/duplicate-enum-source.stderr b/subprojects/thiserror/tests/ui/duplicate-enum-source.stderr
new file mode 100644
index 0000000..4a4b2d3
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-enum-source.stderr
@@ -0,0 +1,5 @@
+error: duplicate #[source] attribute
+ --> tests/ui/duplicate-enum-source.rs:8:9
+  |
+8 |         #[source]
+  |         ^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/duplicate-fmt.rs b/subprojects/thiserror/tests/ui/duplicate-fmt.rs
new file mode 100644
index 0000000..32f7a23
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-fmt.rs
@@ -0,0 +1,23 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("...")]
+#[error("...")]
+pub struct Error;
+
+#[derive(Error, Debug)]
+#[error(fmt = core::fmt::Octal::fmt)]
+#[error(fmt = core::fmt::LowerHex::fmt)]
+pub enum FmtFmt {}
+
+#[derive(Error, Debug)]
+#[error(fmt = core::fmt::Octal::fmt)]
+#[error(transparent)]
+pub enum FmtTransparent {}
+
+#[derive(Error, Debug)]
+#[error(fmt = core::fmt::Octal::fmt)]
+#[error("...")]
+pub enum FmtDisplay {}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/duplicate-fmt.stderr b/subprojects/thiserror/tests/ui/duplicate-fmt.stderr
new file mode 100644
index 0000000..a6c9932
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-fmt.stderr
@@ -0,0 +1,23 @@
+error: only one #[error(...)] attribute is allowed
+ --> tests/ui/duplicate-fmt.rs:5:1
+  |
+5 | #[error("...")]
+  | ^^^^^^^^^^^^^^^
+
+error: duplicate #[error(fmt = ...)] attribute
+  --> tests/ui/duplicate-fmt.rs:10:1
+   |
+10 | #[error(fmt = core::fmt::LowerHex::fmt)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: cannot have both #[error(transparent)] and #[error(fmt = ...)]
+  --> tests/ui/duplicate-fmt.rs:14:1
+   |
+14 | #[error(fmt = core::fmt::Octal::fmt)]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: cannot have both #[error(fmt = ...)] and a format arguments attribute
+  --> tests/ui/duplicate-fmt.rs:20:1
+   |
+20 | #[error("...")]
+   | ^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/duplicate-struct-source.rs b/subprojects/thiserror/tests/ui/duplicate-struct-source.rs
new file mode 100644
index 0000000..569df8d
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-struct-source.rs
@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub struct ErrorStruct {
+    #[source]
+    a: std::io::Error,
+    #[source]
+    b: anyhow::Error,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/duplicate-struct-source.stderr b/subprojects/thiserror/tests/ui/duplicate-struct-source.stderr
new file mode 100644
index 0000000..c8de574
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-struct-source.stderr
@@ -0,0 +1,5 @@
+error: duplicate #[source] attribute
+ --> tests/ui/duplicate-struct-source.rs:7:5
+  |
+7 |     #[source]
+  |     ^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/duplicate-transparent.rs b/subprojects/thiserror/tests/ui/duplicate-transparent.rs
new file mode 100644
index 0000000..49c0e46
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-transparent.rs
@@ -0,0 +1,8 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(transparent)]
+#[error(transparent)]
+pub struct Error(anyhow::Error);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/duplicate-transparent.stderr b/subprojects/thiserror/tests/ui/duplicate-transparent.stderr
new file mode 100644
index 0000000..a830879
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/duplicate-transparent.stderr
@@ -0,0 +1,5 @@
+error: duplicate #[error(transparent)] attribute
+ --> tests/ui/duplicate-transparent.rs:5:1
+  |
+5 | #[error(transparent)]
+  | ^^^^^^^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/expression-fallback.rs b/subprojects/thiserror/tests/ui/expression-fallback.rs
new file mode 100644
index 0000000..7269129
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/expression-fallback.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("".yellow)]
+pub struct ArgError;
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/expression-fallback.stderr b/subprojects/thiserror/tests/ui/expression-fallback.stderr
new file mode 100644
index 0000000..8d22c3a
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/expression-fallback.stderr
@@ -0,0 +1,24 @@
+error: expected `,`, found `.`
+ --> tests/ui/expression-fallback.rs:4:11
+  |
+4 | #[error("".yellow)]
+  |           ^ expected `,`
+
+error: argument never used
+ --> tests/ui/expression-fallback.rs:4:12
+  |
+4 | #[error("".yellow)]
+  |         -- ^^^^^^ argument never used
+  |         |
+  |         formatting specifier missing
+  |
+help: format specifiers use curly braces, consider adding a format specifier
+  |
+4 | #[error("{}".yellow)]
+  |          ++
+
+error[E0425]: cannot find value `yellow` in this scope
+ --> tests/ui/expression-fallback.rs:4:12
+  |
+4 | #[error("".yellow)]
+  |            ^^^^^^ not found in this scope
diff --git a/subprojects/thiserror/tests/ui/fallback-impl-with-display.rs b/subprojects/thiserror/tests/ui/fallback-impl-with-display.rs
new file mode 100644
index 0000000..23dcf28
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/fallback-impl-with-display.rs
@@ -0,0 +1,14 @@
+use core::fmt::{self, Display};
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error]
+pub struct MyError;
+
+impl Display for MyError {
+    fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+        unimplemented!()
+    }
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/fallback-impl-with-display.stderr b/subprojects/thiserror/tests/ui/fallback-impl-with-display.stderr
new file mode 100644
index 0000000..6bd3730
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/fallback-impl-with-display.stderr
@@ -0,0 +1,16 @@
+error: expected attribute arguments in parentheses: #[error(...)]
+ --> tests/ui/fallback-impl-with-display.rs:5:3
+  |
+5 | #[error]
+  |   ^^^^^
+
+error[E0119]: conflicting implementations of trait `std::fmt::Display` for type `MyError`
+ --> tests/ui/fallback-impl-with-display.rs:4:10
+  |
+4 | #[derive(Error, Debug)]
+  |          ^^^^^ conflicting implementation for `MyError`
+...
+8 | impl Display for MyError {
+  | ------------------------ first implementation here
+  |
+  = note: this error originates in the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/subprojects/thiserror/tests/ui/from-backtrace-backtrace.rs b/subprojects/thiserror/tests/ui/from-backtrace-backtrace.rs
new file mode 100644
index 0000000..3b781ac
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/from-backtrace-backtrace.rs
@@ -0,0 +1,15 @@
+// https://github.com/dtolnay/thiserror/issues/163
+
+use std::backtrace::Backtrace;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct Error(
+    #[from]
+    #[backtrace]
+    std::io::Error,
+    Backtrace,
+);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/from-backtrace-backtrace.stderr b/subprojects/thiserror/tests/ui/from-backtrace-backtrace.stderr
new file mode 100644
index 0000000..5c0b9a3
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/from-backtrace-backtrace.stderr
@@ -0,0 +1,5 @@
+error: deriving From requires no fields other than source and backtrace
+ --> tests/ui/from-backtrace-backtrace.rs:9:5
+  |
+9 |     #[from]
+  |     ^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/from-not-source.rs b/subprojects/thiserror/tests/ui/from-not-source.rs
new file mode 100644
index 0000000..ad72867
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/from-not-source.rs
@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub struct Error {
+    #[source]
+    source: std::io::Error,
+    #[from]
+    other: anyhow::Error,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/from-not-source.stderr b/subprojects/thiserror/tests/ui/from-not-source.stderr
new file mode 100644
index 0000000..9713601
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/from-not-source.stderr
@@ -0,0 +1,5 @@
+error: #[from] is only supported on the source field, not any other field
+ --> tests/ui/from-not-source.rs:7:5
+  |
+7 |     #[from]
+  |     ^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/invalid-input-impl-anyway.rs b/subprojects/thiserror/tests/ui/invalid-input-impl-anyway.rs
new file mode 100644
index 0000000..0a0bcbe
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/invalid-input-impl-anyway.rs
@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error]
+pub struct MyError;
+
+fn main() {
+    // No error on the following line. Thiserror emits an Error impl despite the
+    // bad attribute.
+    _ = &MyError as &dyn std::error::Error;
+}
diff --git a/subprojects/thiserror/tests/ui/invalid-input-impl-anyway.stderr b/subprojects/thiserror/tests/ui/invalid-input-impl-anyway.stderr
new file mode 100644
index 0000000..b98c31e
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/invalid-input-impl-anyway.stderr
@@ -0,0 +1,5 @@
+error: expected attribute arguments in parentheses: #[error(...)]
+ --> tests/ui/invalid-input-impl-anyway.rs:4:3
+  |
+4 | #[error]
+  |   ^^^^^
diff --git a/subprojects/thiserror/tests/ui/lifetime.rs b/subprojects/thiserror/tests/ui/lifetime.rs
new file mode 100644
index 0000000..a82909d
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/lifetime.rs
@@ -0,0 +1,24 @@
+use core::fmt::Debug;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("error")]
+struct Error<'a>(#[from] Inner<'a>);
+
+#[derive(Error, Debug)]
+#[error("{0}")]
+struct Inner<'a>(&'a str);
+
+#[derive(Error, Debug)]
+enum Enum<'a> {
+    #[error("error")]
+    Foo(#[from] Generic<&'a str>),
+}
+
+#[derive(Error, Debug)]
+#[error("{0:?}")]
+struct Generic<T: Debug>(T);
+
+fn main() -> Result<(), Error<'static>> {
+    Err(Error(Inner("some text")))
+}
diff --git a/subprojects/thiserror/tests/ui/lifetime.stderr b/subprojects/thiserror/tests/ui/lifetime.stderr
new file mode 100644
index 0000000..8b58136
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/lifetime.stderr
@@ -0,0 +1,11 @@
+error: non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static
+ --> tests/ui/lifetime.rs:6:26
+  |
+6 | struct Error<'a>(#[from] Inner<'a>);
+  |                          ^^^^^^^^^
+
+error: non-static lifetimes are not allowed in the source of an error, because std::error::Error requires the source is dyn Error + 'static
+  --> tests/ui/lifetime.rs:15:17
+   |
+15 |     Foo(#[from] Generic<&'a str>),
+   |                 ^^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/missing-display.rs b/subprojects/thiserror/tests/ui/missing-display.rs
new file mode 100644
index 0000000..31e23fe
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/missing-display.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum MyError {
+    First,
+    Second,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/missing-display.stderr b/subprojects/thiserror/tests/ui/missing-display.stderr
new file mode 100644
index 0000000..fe7472e
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/missing-display.stderr
@@ -0,0 +1,19 @@
+error[E0277]: `MyError` doesn't implement `std::fmt::Display`
+ --> tests/ui/missing-display.rs:4:10
+  |
+3 | #[derive(Error, Debug)]
+  |          ----- in this derive macro expansion
+4 | pub enum MyError {
+  |          ^^^^^^^ unsatisfied trait bound
+  |
+help: the trait `std::fmt::Display` is not implemented for `MyError`
+ --> tests/ui/missing-display.rs:4:1
+  |
+4 | pub enum MyError {
+  | ^^^^^^^^^^^^^^^^
+note: required by a bound in `std::error::Error`
+ --> $RUST/core/src/error.rs
+  |
+  | pub trait Error: Debug + Display {
+  |                          ^^^^^^^ required by this bound in `Error`
+  = note: this error originates in the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/subprojects/thiserror/tests/ui/missing-fmt.rs b/subprojects/thiserror/tests/ui/missing-fmt.rs
new file mode 100644
index 0000000..d52fbdf
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/missing-fmt.rs
@@ -0,0 +1,10 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error("...")]
+    A(usize),
+    B(usize),
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/missing-fmt.stderr b/subprojects/thiserror/tests/ui/missing-fmt.stderr
new file mode 100644
index 0000000..c0be373
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/missing-fmt.stderr
@@ -0,0 +1,5 @@
+error: missing #[error("...")] display attribute
+ --> tests/ui/missing-fmt.rs:7:5
+  |
+7 |     B(usize),
+  |     ^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/no-display.rs b/subprojects/thiserror/tests/ui/no-display.rs
new file mode 100644
index 0000000..d804e00
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/no-display.rs
@@ -0,0 +1,18 @@
+use thiserror::Error;
+
+#[derive(Debug)]
+struct NoDisplay;
+
+#[derive(Error, Debug)]
+#[error("thread: {thread}")]
+pub struct Error {
+    thread: NoDisplay,
+}
+
+#[derive(Error, Debug)]
+#[error("thread: {thread:o}")]
+pub struct ErrorOctal {
+    thread: NoDisplay,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/no-display.stderr b/subprojects/thiserror/tests/ui/no-display.stderr
new file mode 100644
index 0000000..9750582
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/no-display.stderr
@@ -0,0 +1,46 @@
+error[E0599]: the method `as_display` exists for reference `&NoDisplay`, but its trait bounds were not satisfied
+ --> tests/ui/no-display.rs:7:9
+  |
+4 | struct NoDisplay;
+  | ---------------- doesn't satisfy `NoDisplay: std::fmt::Display`
+...
+7 | #[error("thread: {thread}")]
+  |         ^^^^^^^^^^^^^^^^^^ method cannot be called on `&NoDisplay` due to unsatisfied trait bounds
+  |
+  = note: the following trait bounds were not satisfied:
+          `NoDisplay: std::fmt::Display`
+          which is required by `&NoDisplay: AsDisplay<'_>`
+note: the trait `std::fmt::Display` must be implemented
+ --> $RUST/core/src/fmt/mod.rs
+  |
+  | pub trait Display: PointeeSized {
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  = help: items from traits can only be used if the trait is implemented and in scope
+  = note: the following trait defines an item `as_display`, perhaps you need to implement it:
+          candidate #1: `AsDisplay`
+
+error[E0277]: the trait bound `NoDisplay: Octal` is not satisfied
+  --> tests/ui/no-display.rs:13:9
+   |
+12 | #[derive(Error, Debug)]
+   |          ----- in this derive macro expansion
+13 | #[error("thread: {thread:o}")]
+   |         ^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
+   |
+help: the trait `Octal` is not implemented for `NoDisplay`
+  --> tests/ui/no-display.rs:4:1
+   |
+ 4 | struct NoDisplay;
+   | ^^^^^^^^^^^^^^^^
+   = help: the following other types implement trait `Octal`:
+             &T
+             &mut T
+             NonZero<T>
+             Saturating<T>
+             Wrapping<T>
+             i128
+             i16
+             i32
+           and $N others
+   = note: required for `&NoDisplay` to implement `Octal`
+   = note: this error originates in the macro `$crate::format_args` which comes from the expansion of the derive macro `Error` (in Nightly builds, run with -Z macro-backtrace for more info)
diff --git a/subprojects/thiserror/tests/ui/numbered-positional-tuple.rs b/subprojects/thiserror/tests/ui/numbered-positional-tuple.rs
new file mode 100644
index 0000000..6deb658
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/numbered-positional-tuple.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("invalid rdo_lookahead_frames {0} (expected < {})", i32::MAX)]
+pub struct Error(u32);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/numbered-positional-tuple.stderr b/subprojects/thiserror/tests/ui/numbered-positional-tuple.stderr
new file mode 100644
index 0000000..ab13371
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/numbered-positional-tuple.stderr
@@ -0,0 +1,5 @@
+error: ambiguous reference to positional arguments by number in a tuple struct; change this to a named argument
+ --> tests/ui/numbered-positional-tuple.rs:4:61
+  |
+4 | #[error("invalid rdo_lookahead_frames {0} (expected < {})", i32::MAX)]
+  |                                                             ^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/raw-identifier.rs b/subprojects/thiserror/tests/ui/raw-identifier.rs
new file mode 100644
index 0000000..e7e66d0
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/raw-identifier.rs
@@ -0,0 +1,12 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("error: {r#fn}")]
+pub struct Error {
+    r#fn: &'static str,
+}
+
+fn main() {
+    let r#fn = "...";
+    let _ = format!("error: {r#fn}");
+}
diff --git a/subprojects/thiserror/tests/ui/raw-identifier.stderr b/subprojects/thiserror/tests/ui/raw-identifier.stderr
new file mode 100644
index 0000000..a3ce94d
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/raw-identifier.stderr
@@ -0,0 +1,21 @@
+error: invalid format string: raw identifiers are not supported
+ --> tests/ui/raw-identifier.rs:4:18
+  |
+4 | #[error("error: {r#fn}")]
+  |                  --^^
+  |                  |
+  |                  raw identifier used here in format string
+  |                  help: remove the `r#`
+  |
+  = note: identifiers in format strings can be keywords and don't need to be prefixed with `r#`
+
+error: invalid format string: raw identifiers are not supported
+  --> tests/ui/raw-identifier.rs:11:30
+   |
+11 |     let _ = format!("error: {r#fn}");
+   |                              --^^
+   |                              |
+   |                              raw identifier used here in format string
+   |                              help: remove the `r#`
+   |
+   = note: identifiers in format strings can be keywords and don't need to be prefixed with `r#`
diff --git a/subprojects/thiserror/tests/ui/same-from-type.rs b/subprojects/thiserror/tests/ui/same-from-type.rs
new file mode 100644
index 0000000..0ebdf45
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/same-from-type.rs
@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error("failed to open")]
+    OpenFile(#[from] std::io::Error),
+    #[error("failed to close")]
+    CloseFile(#[from] std::io::Error),
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/same-from-type.stderr b/subprojects/thiserror/tests/ui/same-from-type.stderr
new file mode 100644
index 0000000..a655163
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/same-from-type.stderr
@@ -0,0 +1,8 @@
+error[E0119]: conflicting implementations of trait `From<std::io::Error>` for type `Error`
+ --> tests/ui/same-from-type.rs:8:15
+  |
+6 |     OpenFile(#[from] std::io::Error),
+  |              ------- first implementation here
+7 |     #[error("failed to close")]
+8 |     CloseFile(#[from] std::io::Error),
+  |               ^^^^^^^ conflicting implementation for `Error`
diff --git a/subprojects/thiserror/tests/ui/source-enum-not-error.rs b/subprojects/thiserror/tests/ui/source-enum-not-error.rs
new file mode 100644
index 0000000..dae2285
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-enum-not-error.rs
@@ -0,0 +1,12 @@
+use thiserror::Error;
+
+#[derive(Debug)]
+pub struct NotError;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub enum ErrorEnum {
+    Broken { source: NotError },
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/source-enum-not-error.stderr b/subprojects/thiserror/tests/ui/source-enum-not-error.stderr
new file mode 100644
index 0000000..649d77d
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-enum-not-error.stderr
@@ -0,0 +1,22 @@
+error[E0599]: the method `as_dyn_error` exists for reference `&NotError`, but its trait bounds were not satisfied
+ --> tests/ui/source-enum-not-error.rs:9:14
+  |
+4 | pub struct NotError;
+  | ------------------- doesn't satisfy `NotError: AsDynError<'_>` or `NotError: std::error::Error`
+...
+9 |     Broken { source: NotError },
+  |              ^^^^^^ method cannot be called on `&NotError` due to unsatisfied trait bounds
+  |
+  = note: the following trait bounds were not satisfied:
+          `NotError: std::error::Error`
+          which is required by `NotError: AsDynError<'_>`
+          `&NotError: std::error::Error`
+          which is required by `&NotError: AsDynError<'_>`
+note: the trait `std::error::Error` must be implemented
+ --> $RUST/core/src/error.rs
+  |
+  | pub trait Error: Debug + Display {
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  = help: items from traits can only be used if the trait is implemented and in scope
+  = note: the following trait defines an item `as_dyn_error`, perhaps you need to implement it:
+          candidate #1: `AsDynError`
diff --git a/subprojects/thiserror/tests/ui/source-enum-unnamed-field-not-error.rs b/subprojects/thiserror/tests/ui/source-enum-unnamed-field-not-error.rs
new file mode 100644
index 0000000..a877c2c
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-enum-unnamed-field-not-error.rs
@@ -0,0 +1,12 @@
+use thiserror::Error;
+
+#[derive(Debug)]
+pub struct NotError;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub enum ErrorEnum {
+    Broken(#[source] NotError),
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/source-enum-unnamed-field-not-error.stderr b/subprojects/thiserror/tests/ui/source-enum-unnamed-field-not-error.stderr
new file mode 100644
index 0000000..dc97a4b
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-enum-unnamed-field-not-error.stderr
@@ -0,0 +1,22 @@
+error[E0599]: the method `as_dyn_error` exists for reference `&NotError`, but its trait bounds were not satisfied
+ --> tests/ui/source-enum-unnamed-field-not-error.rs:9:12
+  |
+4 | pub struct NotError;
+  | ------------------- doesn't satisfy `NotError: AsDynError<'_>` or `NotError: std::error::Error`
+...
+9 |     Broken(#[source] NotError),
+  |            ^^^^^^^^^ method cannot be called on `&NotError` due to unsatisfied trait bounds
+  |
+  = note: the following trait bounds were not satisfied:
+          `NotError: std::error::Error`
+          which is required by `NotError: AsDynError<'_>`
+          `&NotError: std::error::Error`
+          which is required by `&NotError: AsDynError<'_>`
+note: the trait `std::error::Error` must be implemented
+ --> $RUST/core/src/error.rs
+  |
+  | pub trait Error: Debug + Display {
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  = help: items from traits can only be used if the trait is implemented and in scope
+  = note: the following trait defines an item `as_dyn_error`, perhaps you need to implement it:
+          candidate #1: `AsDynError`
diff --git a/subprojects/thiserror/tests/ui/source-struct-not-error.rs b/subprojects/thiserror/tests/ui/source-struct-not-error.rs
new file mode 100644
index 0000000..d59df1e
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-struct-not-error.rs
@@ -0,0 +1,12 @@
+use thiserror::Error;
+
+#[derive(Debug)]
+struct NotError;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct ErrorStruct {
+    source: NotError,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/source-struct-not-error.stderr b/subprojects/thiserror/tests/ui/source-struct-not-error.stderr
new file mode 100644
index 0000000..07cd67a
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-struct-not-error.stderr
@@ -0,0 +1,20 @@
+error[E0599]: the method `as_dyn_error` exists for struct `NotError`, but its trait bounds were not satisfied
+ --> tests/ui/source-struct-not-error.rs:9:5
+  |
+4 | struct NotError;
+  | --------------- method `as_dyn_error` not found for this struct because it doesn't satisfy `NotError: AsDynError<'_>` or `NotError: std::error::Error`
+...
+9 |     source: NotError,
+  |     ^^^^^^ method cannot be called on `NotError` due to unsatisfied trait bounds
+  |
+  = note: the following trait bounds were not satisfied:
+          `NotError: std::error::Error`
+          which is required by `NotError: AsDynError<'_>`
+note: the trait `std::error::Error` must be implemented
+ --> $RUST/core/src/error.rs
+  |
+  | pub trait Error: Debug + Display {
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  = help: items from traits can only be used if the trait is implemented and in scope
+  = note: the following trait defines an item `as_dyn_error`, perhaps you need to implement it:
+          candidate #1: `AsDynError`
diff --git a/subprojects/thiserror/tests/ui/source-struct-unnamed-field-not-error.rs b/subprojects/thiserror/tests/ui/source-struct-unnamed-field-not-error.rs
new file mode 100644
index 0000000..160b6b2
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-struct-unnamed-field-not-error.rs
@@ -0,0 +1,10 @@
+use thiserror::Error;
+
+#[derive(Debug)]
+struct NotError;
+
+#[derive(Error, Debug)]
+#[error("...")]
+pub struct ErrorStruct(#[source] NotError);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/source-struct-unnamed-field-not-error.stderr b/subprojects/thiserror/tests/ui/source-struct-unnamed-field-not-error.stderr
new file mode 100644
index 0000000..1f5350b
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/source-struct-unnamed-field-not-error.stderr
@@ -0,0 +1,20 @@
+error[E0599]: the method `as_dyn_error` exists for struct `NotError`, but its trait bounds were not satisfied
+ --> tests/ui/source-struct-unnamed-field-not-error.rs:8:24
+  |
+4 | struct NotError;
+  | --------------- method `as_dyn_error` not found for this struct because it doesn't satisfy `NotError: AsDynError<'_>` or `NotError: std::error::Error`
+...
+8 | pub struct ErrorStruct(#[source] NotError);
+  |                        ^^^^^^^^^ method cannot be called on `NotError` due to unsatisfied trait bounds
+  |
+  = note: the following trait bounds were not satisfied:
+          `NotError: std::error::Error`
+          which is required by `NotError: AsDynError<'_>`
+note: the trait `std::error::Error` must be implemented
+ --> $RUST/core/src/error.rs
+  |
+  | pub trait Error: Debug + Display {
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  = help: items from traits can only be used if the trait is implemented and in scope
+  = note: the following trait defines an item `as_dyn_error`, perhaps you need to implement it:
+          candidate #1: `AsDynError`
diff --git a/subprojects/thiserror/tests/ui/struct-with-fmt.rs b/subprojects/thiserror/tests/ui/struct-with-fmt.rs
new file mode 100644
index 0000000..73bf79f
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/struct-with-fmt.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(fmt = core::fmt::Octal::fmt)]
+pub struct Error(i32);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/struct-with-fmt.stderr b/subprojects/thiserror/tests/ui/struct-with-fmt.stderr
new file mode 100644
index 0000000..00463be
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/struct-with-fmt.stderr
@@ -0,0 +1,5 @@
+error: #[error(fmt = ...)] is only supported in enums; for a struct, handwrite your own Display impl
+ --> tests/ui/struct-with-fmt.rs:4:1
+  |
+4 | #[error(fmt = core::fmt::Octal::fmt)]
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/transparent-display.rs b/subprojects/thiserror/tests/ui/transparent-display.rs
new file mode 100644
index 0000000..2a59f18
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-display.rs
@@ -0,0 +1,8 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(transparent)]
+#[error("...")]
+pub struct Error(anyhow::Error);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-display.stderr b/subprojects/thiserror/tests/ui/transparent-display.stderr
new file mode 100644
index 0000000..54d958b
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-display.stderr
@@ -0,0 +1,5 @@
+error: cannot have both #[error(transparent)] and a display attribute
+ --> tests/ui/transparent-display.rs:5:1
+  |
+5 | #[error("...")]
+  | ^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-many.rs b/subprojects/thiserror/tests/ui/transparent-enum-many.rs
new file mode 100644
index 0000000..e2a73a4
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-many.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error(transparent)]
+    Other(anyhow::Error, String),
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-many.stderr b/subprojects/thiserror/tests/ui/transparent-enum-many.stderr
new file mode 100644
index 0000000..a9adfa5
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-many.stderr
@@ -0,0 +1,6 @@
+error: #[error(transparent)] requires exactly one field
+ --> tests/ui/transparent-enum-many.rs:5:5
+  |
+5 | /     #[error(transparent)]
+6 | |     Other(anyhow::Error, String),
+  | |________________________________^
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-not-error.rs b/subprojects/thiserror/tests/ui/transparent-enum-not-error.rs
new file mode 100644
index 0000000..80ccfc9
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-not-error.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error(transparent)]
+    Other { message: String },
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-not-error.stderr b/subprojects/thiserror/tests/ui/transparent-enum-not-error.stderr
new file mode 100644
index 0000000..bb836d4
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-not-error.stderr
@@ -0,0 +1,20 @@
+error[E0599]: the method `as_dyn_error` exists for reference `&String`, but its trait bounds were not satisfied
+ --> tests/ui/transparent-enum-not-error.rs:5:13
+  |
+5 |     #[error(transparent)]
+  |             ^^^^^^^^^^^ method cannot be called on `&String` due to unsatisfied trait bounds
+  |
+ ::: $RUST/alloc/src/string.rs
+  |
+  | pub struct String {
+  | ----------------- doesn't satisfy `String: AsDynError<'_>` or `String: std::error::Error`
+  |
+  = note: the following trait bounds were not satisfied:
+          `String: std::error::Error`
+          which is required by `String: AsDynError<'_>`
+          `&String: std::error::Error`
+          which is required by `&String: AsDynError<'_>`
+          `str: Sized`
+          which is required by `str: AsDynError<'_>`
+          `str: std::error::Error`
+          which is required by `str: AsDynError<'_>`
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-source.rs b/subprojects/thiserror/tests/ui/transparent-enum-source.rs
new file mode 100644
index 0000000..3849f66
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-source.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error(transparent)]
+    Other(#[source] anyhow::Error),
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-source.stderr b/subprojects/thiserror/tests/ui/transparent-enum-source.stderr
new file mode 100644
index 0000000..ccb9067
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-source.stderr
@@ -0,0 +1,5 @@
+error: transparent variant can't contain #[source]
+ --> tests/ui/transparent-enum-source.rs:6:11
+  |
+6 |     Other(#[source] anyhow::Error),
+  |           ^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-unnamed-field-not-error.rs b/subprojects/thiserror/tests/ui/transparent-enum-unnamed-field-not-error.rs
new file mode 100644
index 0000000..87c32e0
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-unnamed-field-not-error.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error(transparent)]
+    Other(String),
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-enum-unnamed-field-not-error.stderr b/subprojects/thiserror/tests/ui/transparent-enum-unnamed-field-not-error.stderr
new file mode 100644
index 0000000..f337c59
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-enum-unnamed-field-not-error.stderr
@@ -0,0 +1,20 @@
+error[E0599]: the method `as_dyn_error` exists for reference `&String`, but its trait bounds were not satisfied
+ --> tests/ui/transparent-enum-unnamed-field-not-error.rs:5:13
+  |
+5 |     #[error(transparent)]
+  |             ^^^^^^^^^^^ method cannot be called on `&String` due to unsatisfied trait bounds
+  |
+ ::: $RUST/alloc/src/string.rs
+  |
+  | pub struct String {
+  | ----------------- doesn't satisfy `String: AsDynError<'_>` or `String: std::error::Error`
+  |
+  = note: the following trait bounds were not satisfied:
+          `String: std::error::Error`
+          which is required by `String: AsDynError<'_>`
+          `&String: std::error::Error`
+          which is required by `&String: AsDynError<'_>`
+          `str: Sized`
+          which is required by `str: AsDynError<'_>`
+          `str: std::error::Error`
+          which is required by `str: AsDynError<'_>`
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-many.rs b/subprojects/thiserror/tests/ui/transparent-struct-many.rs
new file mode 100644
index 0000000..18f2466
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-many.rs
@@ -0,0 +1,10 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(transparent)]
+pub struct Error {
+    inner: anyhow::Error,
+    what: String,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-many.stderr b/subprojects/thiserror/tests/ui/transparent-struct-many.stderr
new file mode 100644
index 0000000..c0e3806
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-many.stderr
@@ -0,0 +1,5 @@
+error: #[error(transparent)] requires exactly one field
+ --> tests/ui/transparent-struct-many.rs:4:1
+  |
+4 | #[error(transparent)]
+  | ^^^^^^^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-not-error.rs b/subprojects/thiserror/tests/ui/transparent-struct-not-error.rs
new file mode 100644
index 0000000..811ff53
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-not-error.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(transparent)]
+pub struct Error {
+    message: String,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-not-error.stderr b/subprojects/thiserror/tests/ui/transparent-struct-not-error.stderr
new file mode 100644
index 0000000..ee50d03
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-not-error.stderr
@@ -0,0 +1,18 @@
+error[E0599]: the method `as_dyn_error` exists for struct `String`, but its trait bounds were not satisfied
+ --> tests/ui/transparent-struct-not-error.rs:4:9
+  |
+4 | #[error(transparent)]
+  |         ^^^^^^^^^^^ method cannot be called on `String` due to unsatisfied trait bounds
+  |
+ ::: $RUST/alloc/src/string.rs
+  |
+  | pub struct String {
+  | ----------------- doesn't satisfy `String: AsDynError<'_>` or `String: std::error::Error`
+  |
+  = note: the following trait bounds were not satisfied:
+          `String: std::error::Error`
+          which is required by `String: AsDynError<'_>`
+          `str: Sized`
+          which is required by `str: AsDynError<'_>`
+          `str: std::error::Error`
+          which is required by `str: AsDynError<'_>`
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-source.rs b/subprojects/thiserror/tests/ui/transparent-struct-source.rs
new file mode 100644
index 0000000..d4512c2
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-source.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(transparent)]
+pub struct Error(#[source] anyhow::Error);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-source.stderr b/subprojects/thiserror/tests/ui/transparent-struct-source.stderr
new file mode 100644
index 0000000..3012ca3
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-source.stderr
@@ -0,0 +1,5 @@
+error: transparent error struct can't contain #[source]
+ --> tests/ui/transparent-struct-source.rs:5:18
+  |
+5 | pub struct Error(#[source] anyhow::Error);
+  |                  ^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-unnamed-field-not-error.rs b/subprojects/thiserror/tests/ui/transparent-struct-unnamed-field-not-error.rs
new file mode 100644
index 0000000..b4f7fbb
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-unnamed-field-not-error.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error(transparent)]
+pub struct Error(String);
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/transparent-struct-unnamed-field-not-error.stderr b/subprojects/thiserror/tests/ui/transparent-struct-unnamed-field-not-error.stderr
new file mode 100644
index 0000000..c3d6c00
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/transparent-struct-unnamed-field-not-error.stderr
@@ -0,0 +1,18 @@
+error[E0599]: the method `as_dyn_error` exists for struct `String`, but its trait bounds were not satisfied
+ --> tests/ui/transparent-struct-unnamed-field-not-error.rs:4:9
+  |
+4 | #[error(transparent)]
+  |         ^^^^^^^^^^^ method cannot be called on `String` due to unsatisfied trait bounds
+  |
+ ::: $RUST/alloc/src/string.rs
+  |
+  | pub struct String {
+  | ----------------- doesn't satisfy `String: AsDynError<'_>` or `String: std::error::Error`
+  |
+  = note: the following trait bounds were not satisfied:
+          `String: std::error::Error`
+          which is required by `String: AsDynError<'_>`
+          `str: Sized`
+          which is required by `str: AsDynError<'_>`
+          `str: std::error::Error`
+          which is required by `str: AsDynError<'_>`
diff --git a/subprojects/thiserror/tests/ui/unconditional-recursion.rs b/subprojects/thiserror/tests/ui/unconditional-recursion.rs
new file mode 100644
index 0000000..035b15e
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/unconditional-recursion.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("{self}")]
+pub struct Error;
+
+fn main() {
+    __FAIL__;
+}
diff --git a/subprojects/thiserror/tests/ui/unconditional-recursion.stderr b/subprojects/thiserror/tests/ui/unconditional-recursion.stderr
new file mode 100644
index 0000000..568e891
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/unconditional-recursion.stderr
@@ -0,0 +1,21 @@
+error[E0425]: cannot find value `__FAIL__` in this scope
+ --> tests/ui/unconditional-recursion.rs:8:5
+  |
+8 |     __FAIL__;
+  |     ^^^^^^^^ not found in this scope
+
+warning: function cannot return without recursing
+ --> tests/ui/unconditional-recursion.rs:4:9
+  |
+4 | #[error("{self}")]
+  |         ^^^^^^^^
+  |         |
+  |         cannot return without recursing
+  |         recursive call site
+  |
+  = help: a `loop` may express intention better if this is on purpose
+note: the lint level is defined here
+ --> tests/ui/unconditional-recursion.rs:4:9
+  |
+4 | #[error("{self}")]
+  |         ^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/unexpected-field-fmt.rs b/subprojects/thiserror/tests/ui/unexpected-field-fmt.rs
new file mode 100644
index 0000000..7c439d9
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/unexpected-field-fmt.rs
@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum Error {
+    What {
+        #[error("...")]
+        io: std::io::Error,
+    },
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/unexpected-field-fmt.stderr b/subprojects/thiserror/tests/ui/unexpected-field-fmt.stderr
new file mode 100644
index 0000000..bf3c24d
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/unexpected-field-fmt.stderr
@@ -0,0 +1,5 @@
+error: not expected here; the #[error(...)] attribute belongs on top of a struct or an enum variant
+ --> tests/ui/unexpected-field-fmt.rs:6:9
+  |
+6 |         #[error("...")]
+  |         ^^^^^^^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/unexpected-struct-source.rs b/subprojects/thiserror/tests/ui/unexpected-struct-source.rs
new file mode 100644
index 0000000..f396494
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/unexpected-struct-source.rs
@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[source]
+pub struct Error;
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/unexpected-struct-source.stderr b/subprojects/thiserror/tests/ui/unexpected-struct-source.stderr
new file mode 100644
index 0000000..6f15841
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/unexpected-struct-source.stderr
@@ -0,0 +1,5 @@
+error: not expected here; the #[source] attribute belongs on a specific field
+ --> tests/ui/unexpected-struct-source.rs:4:1
+  |
+4 | #[source]
+  | ^^^^^^^^^
diff --git a/subprojects/thiserror/tests/ui/union.rs b/subprojects/thiserror/tests/ui/union.rs
new file mode 100644
index 0000000..cd6a934
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/union.rs
@@ -0,0 +1,9 @@
+use thiserror::Error;
+
+#[derive(Error)]
+pub union U {
+    msg: &'static str,
+    num: usize,
+}
+
+fn main() {}
diff --git a/subprojects/thiserror/tests/ui/union.stderr b/subprojects/thiserror/tests/ui/union.stderr
new file mode 100644
index 0000000..3ec4d71
--- /dev/null
+++ b/subprojects/thiserror/tests/ui/union.stderr
@@ -0,0 +1,8 @@
+error: union as errors are not supported
+ --> tests/ui/union.rs:4:1
+  |
+4 | / pub union U {
+5 | |     msg: &'static str,
+6 | |     num: usize,
+7 | | }
+  | |_^