rust: add rust.workspace() skeleton implementation

rust.workspace() is the entry point for global feature resolution.
It loads a Cargo.toml file and ensures that all dependencies will be
built with the correct set of features.

Fixes: #13404
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 27 insertions, 0 deletions

diff --git a/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/Cargo.toml b/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/Cargo.toml
new file mode 100644
index 000000000..b87782264
--- /dev/null
+++ b/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "answer"
+version = "2.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["lib"]
+
+[features]
+large = []
diff --git a/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/meson.build b/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/meson.build
new file mode 100644
index 000000000..dc7df4bba
--- /dev/null
+++ b/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/meson.build
@@ -0,0 +1,7 @@
+project('answer', 'rust', default_options: ['rust_std=2021'])
+
+rust = import('rust')
+
+l = static_library('answer', 'src/lib.rs')
+dep = declare_dependency(link_with: l)
+meson.override_dependency('answer-2-rs', dep)
diff --git a/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/src/lib.rs b/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/src/lib.rs
new file mode 100644
index 000000000..b7a721b05
--- /dev/null
+++ b/test cases/rust/31 rust.workspace package/subprojects/answer-2.1/src/lib.rs
@@ -0,0 +1,10 @@
+pub fn answer() -> u8
+{
+    42
+}
+
+#[cfg(feature = "large")]
+pub fn large_answer() -> u64
+{
+    42
+}