[SwiftParser] Fix lookahead accepting invalid closure signatures #3218
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bhanage-viraj
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hamishknight and
rintaro
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Description
Fixes #3163.
The
canParseClosureSignaturelookahead was previously accepting signatures that started with->or)even if the preceding parameter list was invalid or unbalanced (e.g., missing an opening parenthesis).This change ensures that
canParseClosureSignatureonly consumes a closing parenthesis)if it successfully consumed a matching opening parenthesis(.Risk
Low. This strictly tightens the lookahead logic for invalid syntax.
Testing
Added a regression test in
Issue3163Tests.swiftensuring the "expected 'in' in closure signature" diagnostic no longer appears for the reproduction case.