Handle comments when indenting method chains

Previously, indentation went wrong when the comment on the line above
looked like a method call/member access:

    fn main() {
        // Lorem ipsum lorem ipsum lorem ipsum lorem.ipsum
                                                foo.bar()
    }

With this patch:

    fn main() {
        // Lorem ipsum lorem ipsum lorem ipsum lorem.ipsum
        foo.bar()
    }

Also, a blank line or a comment broke method-chain indentation:

    fn main() {
        something.a.do_it
        // A comment
            .aligned

            .more_alignment();
    }

With this patch:

    fn main() {
        something.a.do_it
        // A comment
                   .aligned

                   .more_alignment();
    }

Note that comments interleaving a method chain are not aligned with the
'.' of the method chain.

1 files changed, 11 insertions, 0 deletions

diff --git a/rust-mode.el b/rust-mode.el
index 2c97433..3f6e279 100644
--- a/rust-mode.el
+++ b/rust-mode.el
@@ -301,6 +301,17 @@ buffer."
     (when (looking-at (concat "\s*\." rust-re-ident))
       (forward-line -1)
       (end-of-line)
+      ;; Keep going up (looking for a line that could contain a method chain)
+      ;; while we're in a comment or on a blank line. Stop when the paren
+      ;; level changes.
+      (let ((level (rust-paren-level)))
+        (while (and (or (rust-in-str-or-cmnt)
+                        ;; Only whitespace (or nothing) from the beginning to
+                        ;; the end of the line.
+                        (looking-back "^\s*" (point-at-bol)))
+                    (= (rust-paren-level) level))
+          (forward-line -1)
+          (end-of-line)))
 
       (let
           ;; skip-dot-identifier is used to position the point at the