Rust 2030 Christmas list: Macro sources in compiler diagnostics

2

AFAIK, the point of -Zmacro-backtrace is precisely this, at least for macro_rules! macros. Indeed, it can, for instance, yield:

error[E0412]: cannot find type `i33` in this scope
 --> /tmp/tmp.FfD3KppAr7/dep/src/lib.rs:6:21
  |
2 | /     macro_rules! create_function {(
3 | |         $name:ident $(,)?
4 | |     ) => (
5 | |         fn foobar() {
6 | |             let x: i33 = 0;
  | |                    ^^^ help: a builtin type with a similar name exists: `i32`
7 | |         }
8 | |     )}
  | |______- in this expansion of `::dep::create_function!`
  |
 ::: src/lib.rs:1:5
  |
1 |       ::dep::create_function!(foobar);
  |       ------------------------------- in this macro invocation

For more information about this error, try `rustc --explain E0412`.
error: could not compile `example` due to previous error

Sadly it doesn't work for procmacro-generated code, so I'd technically amend that wishlist for that exactly :slightly_smiling_face:

  • something like highlighting "virtual source code", the one emitted by the proc macro, formatted by rustc (or rustfmt or whatnot), with an intro saying "from the code emitted by that proc-macro invocation : let x : i33 …
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