diff options
Diffstat (limited to 'src/libsyntax/parse/parser')
| -rw-r--r-- | src/libsyntax/parse/parser/pat.rs | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/src/libsyntax/parse/parser/pat.rs b/src/libsyntax/parse/parser/pat.rs index c168d033781..724edbcfaed 100644 --- a/src/libsyntax/parse/parser/pat.rs +++ b/src/libsyntax/parse/parser/pat.rs @@ -46,11 +46,23 @@ impl<'a> Parser<'a> { /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level. pub(super) fn parse_top_pat(&mut self, gate_or: GateOr) -> PResult<'a, P<Pat>> { // Allow a '|' before the pats (RFCs 1925, 2530, and 2535). - if self.eat_or_separator() && gate_or == GateOr::Yes { - self.sess.gated_spans.or_patterns.borrow_mut().push(self.prev_span); + let gated_leading_vert = self.eat_or_separator() && gate_or == GateOr::Yes; + + // Parse the possibly-or-pattern. + let pat = self.parse_pat_with_or(None, gate_or, TopLevel::Yes)?; + + // If we parsed a leading `|` which should be gated, + // and no other gated or-pattern has been parsed thus far, + // then we should really gate the leading `|`. + // This complicated procedure is done purely for diagnostics UX. + if gated_leading_vert { + let mut or_pattern_spans = self.sess.gated_spans.or_patterns.borrow_mut(); + if or_pattern_spans.is_empty() { + or_pattern_spans.push(self.prev_span); + } } - self.parse_pat_with_or(None, gate_or, TopLevel::Yes) + Ok(pat) } /// Parses a pattern, that may be a or-pattern (e.g. `Foo | Bar` in `Some(Foo | Bar)`). |