Paul Berry
8d2b2a197d
In rare circumstances involving syntax errors, the `parsePattern` method inserts a synthetic token but does not consume any tokens. Usually when this happens it's not a problem, because whatever method is calling `parsePattern` consumes some tokens, so the parser always makes progress. However, when parsing list patterns, after calling `parsePattern`, the parser would look for a `,`, and if it didn't find one, it would supply a synthetic `,` and call `parsePattern` again, resulting in an infinite loop. A similar situation happened with map patterns, though the situation was more complex because in between the calls to `parsePattern`, the parser would also create synthetic key expressions and `:`s. To fix the problem, when parsing a list or map pattern, after the call to `parsePattern`, the parser checks whether any tokens were consumed. If no tokens were consumed, it ignores the next token from the input stream in order to make progress. I also investigated whether there were similar issues with parenthesized/record patterns and switch expressions, since those constructs also consist of a sequence of patterns separated by tokens and other things that could in principle be supplied synthetically. Fortunately, parser recovery doesn't get into an infinite loop in those cases, so I didn't make any further changes. But I did include test cases to make sure. Fixes #52352. Bug: https://github.com/dart-lang/sdk/issues/52352 Change-Id: Idc8140236f6054deb1fd3c862036fe47dd84f30b Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/302803 Reviewed-by: Konstantin Shcheglov <scheglov@google.com> Commit-Queue: Paul Berry <paulberry@google.com>
6 lines
60 B
Dart
6 lines
60 B
Dart
void f(Object? x) {
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switch (x) {
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case {0: if}:
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};
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}
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