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compiler: improve captured metavariables diagnostic

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Adds a link to the relevant part of The Rust Reference in the eror
message, and suggests a possible fix (replacing the fragment specifier
with :tt in the macro definition).

Fixes typos in the original message.

Signed-off-by: Lena Milizé <me@lvmn.org>
This commit is contained in:
Lena Milizé 2023-04-12 11:18:50 +02:00
parent 87a2408b06
commit 4b456cb683
2 changed files with 6 additions and 2 deletions
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4
compiler/rustc_expand/src/mbe/diagnostics.rs
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@ -66,7 +66,9 @@ pub(super) fn failed_to_match_macro<'cx>(
&& (matches!(expected_token.kind, TokenKind::Interpolated(_))
|| matches!(token.kind, TokenKind::Interpolated(_)))
{
err.note("captured metavariables except for `$tt`, `$ident` and `$lifetime` cannot be compared to other tokens");
err.note("captured metavariables except for `:tt`, `:ident` and `:lifetime` cannot be compared to other tokens");
err.note("see https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment for more information");
err.help("try using `:tt` instead in the macro definition");
}
// Check whether there's a missing comma in this macro call, like `println!("{}" a);`