parser: avoid exponential backtracking for parenthesized expressions - #1401
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parser: avoid exponential backtracking for parenthesized expressions#1401Riley-Kilgore wants to merge 1 commit into
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Left-factor the shared '(' prefix of tuples and grouped expressions so
the first interior expression is parsed exactly once, instead of being
fully parsed by the tuple alternative, discarded, and re-parsed as a
group. Nested grouping previously cost O(2^depth); it is now linear.
Preserves tuple, trailing-comma, grouping, parenthesized
sequence/assignment, and NewLineLeftParen semantics, along with source
spans. Adds depth-based regression tests (16–128 levels).
Closes #1377
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Left-factor the shared '(' prefix of tuples and grouped expressions so the first interior expression is parsed exactly once, instead of being fully parsed by the tuple alternative, discarded, and re-parsed as a group. Nested grouping previously cost O(2^depth); it is now linear.
Preserves tuple, trailing-comma, grouping, parenthesized sequence/assignment, and NewLineLeftParen semantics, along with source spans. Adds depth-based regression tests (16–128 levels).
Closes #1377