diff options
| -rw-r--r-- | compiler/rustc_expand/src/mbe/diagnostics.rs | 7 | ||||
| -rw-r--r-- | tests/ui/macros/nonterminal-matching.stderr | 4 |
2 files changed, 9 insertions, 2 deletions
diff --git a/compiler/rustc_expand/src/mbe/diagnostics.rs b/compiler/rustc_expand/src/mbe/diagnostics.rs index 6bc393c6534..35572292271 100644 --- a/compiler/rustc_expand/src/mbe/diagnostics.rs +++ b/compiler/rustc_expand/src/mbe/diagnostics.rs @@ -66,7 +66,12 @@ 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"); + + if !def_span.is_dummy() && !cx.source_map().is_imported(def_span) { + err.help("try using `:tt` instead in the macro definition"); + } } // Check whether there's a missing comma in this macro call, like `println!("{}" a);` diff --git a/tests/ui/macros/nonterminal-matching.stderr b/tests/ui/macros/nonterminal-matching.stderr index 762ecc3207f..c2b047022ed 100644 --- a/tests/ui/macros/nonterminal-matching.stderr +++ b/tests/ui/macros/nonterminal-matching.stderr @@ -18,7 +18,9 @@ LL | macro n(a $nt_item b) { ... LL | complex_nonterminal!(enum E {}); | ------------------------------- in this macro invocation - = note: captured metavariables except for `$tt`, `$ident` and `$lifetime` cannot be compared to other tokens + = note: captured metavariables except for `:tt`, `:ident` and `:lifetime` cannot be compared to other tokens + = note: see <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment> for more information + = help: try using `:tt` instead in the macro definition = note: this error originates in the macro `complex_nonterminal` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error |