diff options
Diffstat (limited to 'src/libsyntax/parse/parser.rs')
| -rw-r--r-- | src/libsyntax/parse/parser.rs | 31 |
1 files changed, 13 insertions, 18 deletions
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs index a2a2c4637c5..8feab373e71 100644 --- a/src/libsyntax/parse/parser.rs +++ b/src/libsyntax/parse/parser.rs @@ -2910,27 +2910,22 @@ impl<'a> Parser<'a> { path: &ast::Path, attrs: &ThinVec<Attribute>, ) -> Option<PResult<'a, P<Expr>>> { - // We don't want to assume it's a struct when encountering `{ <ident>: <ident> }` because - // it could be type ascription, like in `{ ident: u32 }`. - let isnt_ascription = self.look_ahead(1, |t| t.is_ident()) && - self.look_ahead(2, |t| *t == token::Colon) && ( - (self.look_ahead(3, |t| t.is_ident()) && - self.look_ahead(4, |t| *t == token::Comma)) || - self.look_ahead(3, |t| t.is_lit()) || - self.look_ahead(3, |t| *t == token::BinOp(token::Minus)) && - self.look_ahead(4, |t| t.is_lit()) - ); - let could_be_struct = self.look_ahead(1, |t| t.is_ident()) && ( - self.look_ahead(2, |t| *t == token::Colon) && isnt_ascription - || self.look_ahead(2, |t| *t == token::Comma) - // We could also check for `token::CloseDelim(token::Brace)`, but that would - // have false positives in the case of `if x == y { z } { a }`. + let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL); + let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && ( + // `{ ident, ` cannot start a block + self.look_ahead(2, |t| t == &token::Comma) || + self.look_ahead(2, |t| t == &token::Colon) && ( + // `{ ident: token, ` cannot start a block + self.look_ahead(4, |t| t == &token::Comma) || + // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type` + self.look_ahead(3, |t| !t.can_begin_type()) + ) ); - let bad_struct = self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL); - if !bad_struct || could_be_struct { + + if struct_allowed || certainly_not_a_block() { // This is a struct literal, but we don't can't accept them here let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone()); - if let (Ok(expr), true) = (&expr, bad_struct) { + if let (Ok(expr), false) = (&expr, struct_allowed) { let mut err = self.diagnostic().struct_span_err( expr.span, "struct literals are not allowed here", |