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Rollup merge of #108711 - Nilstrieb:nt-note, r=petrochenkov

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Add note when matching token with nonterminal

The current error message is _really_ confusing. The implementation is slightly hacky, but not that much more hacky than all this nonterminal stuff..

r? ``@petrochenkov``
This commit is contained in:
Matthias Krüger 2023-03-11 12:55:42 +01:00 committed by GitHub
commit ef84194744
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2 changed files with 10 additions and 3 deletions
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12
compiler/rustc_expand/src/mbe/diagnostics.rs
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@ -1,12 +1,10 @@
use std::borrow::Cow;
use crate::base::{DummyResult, ExtCtxt, MacResult};
use crate::expand::{parse_ast_fragment, AstFragmentKind};
use crate::mbe::{
macro_parser::{MatcherLoc, NamedParseResult, ParseResult::*, TtParser},
macro_rules::{try_match_macro, Tracker},
};
use rustc_ast::token::{self, Token};
use rustc_ast::token::{self, Token, TokenKind};
use rustc_ast::tokenstream::TokenStream;
use rustc_ast_pretty::pprust;
use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, DiagnosticMessage};
@ -14,6 +12,7 @@ use rustc_parse::parser::{Parser, Recovery};
use rustc_span::source_map::SourceMap;
use rustc_span::symbol::Ident;
use rustc_span::Span;
use std::borrow::Cow;
use super::macro_rules::{parser_from_cx, NoopTracker};
@ -63,6 +62,13 @@ pub(super) fn failed_to_match_macro<'cx>(
err.note(format!("while trying to match {remaining_matcher}"));
}
if let MatcherLoc::Token { token: expected_token } = &remaining_matcher
&& (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");
}
// Check whether there's a missing comma in this macro call, like `println!("{}" a);`
if let Some((arg, comma_span)) = arg.add_comma() {
for lhs in lhses {

1
tests/ui/macros/nonterminal-matching.stderr
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@ -18,6 +18,7 @@ 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: 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