diff options
Diffstat (limited to 'compiler/rustc_expand/src/mbe/macro_parser.rs')
| -rw-r--r-- | compiler/rustc_expand/src/mbe/macro_parser.rs | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs index 0324057e331..ab8e059b7b7 100644 --- a/compiler/rustc_expand/src/mbe/macro_parser.rs +++ b/compiler/rustc_expand/src/mbe/macro_parser.rs @@ -77,7 +77,7 @@ use std::rc::Rc; pub(crate) use NamedMatch::*; pub(crate) use ParseResult::*; -use rustc_ast::token::{self, DocComment, NonterminalKind, Token}; +use rustc_ast::token::{self, DocComment, NonterminalKind, Token, TokenKind}; use rustc_data_structures::fx::FxHashMap; use rustc_errors::ErrorGuaranteed; use rustc_lint_defs::pluralize; @@ -397,7 +397,23 @@ fn token_name_eq(t1: &Token, t2: &Token) -> bool { { ident1.name == ident2.name && is_raw1 == is_raw2 } else { - t1.kind == t2.kind + // Note: we SHOULD NOT use `t1.kind == t2.kind` here, and we should instead compare the + // tokens using the special comparison logic below. + // It makes sure that variants containing `InvisibleOrigin` will + // never compare equal to one another. + // + // When we had AST-based nonterminals we couldn't compare them, and the + // old `Nonterminal` type had an `eq` that always returned false, + // resulting in this restriction: + // <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment> + // This comparison logic emulates that behaviour. We could consider lifting this + // restriction now but there are still cases involving invisible + // delimiters that make it harder than it first appears. + match (t1.kind, t2.kind) { + (TokenKind::OpenInvisible(_) | TokenKind::CloseInvisible(_), _) + | (_, TokenKind::OpenInvisible(_) | TokenKind::CloseInvisible(_)) => false, + (a, b) => a == b, + } } } |