Repository navigation
[mypyc] Fix lambdas in generator expressions consumed by builtins - #22225
Merged
Merged
Conversation
A generator expression that contains a lambda needs a lightweight comprehension scope so that the lambda can capture the loop variables. The special cases for tuple(), set(), sum(), any(), all(), next() and other builtins that consume a generator expression didn't set up the scope, so calling such a lambda raised UnboundLocalError, e.g. tuple((lambda: x) for x in range(3)). Move the scope helper to for_helpers.comprehension_scope and use it in all these special cases. This fixes a regression from #21009 (#21009).
p-sawicki
approved these changes
Oct 19, 2026
Comment on lines
+416
to
+420
| if node not in builder.comprehension_to_fitem: | ||
| yield | ||
| return | ||
|
|
||
| comprehension_fdef = builder.comprehension_to_fitem[node] |
Collaborator
There was a problem hiding this comment.
could avoid the second look-up.
Collaborator
Author
There was a problem hiding this comment.
I'm leaving it as is since this isn't perf critical and the code seems clear.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
A generator expression that contains a lambda needs a lightweight
comprehension scope so that the lambda can capture the loop variables.
The special cases for tuple(), set(), sum(), any(), all(), next() and
other builtins that consume a generator expression didn't set up the
scope, so calling such a lambda raised UnboundLocalError, e.g.
tuple((lambda: x) for x in range(3)).Move the scope helper to for_helpers.comprehension_scope and use it in
all these special cases.
This fixes a regression from #21009.
Also fix a few other closely related issues that came up when testing
the fix.
Add significant test coverage since these features seem to have a
high density of issues.