fix: #20341: [1.19 regression] [mypyc] generator → AssertionError #20371
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BobTheBuidler
commented
Dec 6, 2025
| assert items, "This function does not support empty tuples" | ||
| # Tuple might have elements of different types. | ||
| rtypes = {self.mapper.type_to_rtype(item) for item in target_type.items} | ||
| rtypes = set(map(self.mapper.type_to_rtype, items)) |
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I thought this looks more readable than the brackets when you're scanning quickly
BobTheBuidler
commented
Dec 6, 2025
| return self.get_sequence_type_from_type(target_type.upper_bound) | ||
| elif isinstance(target_type, TupleType): | ||
| items = target_type.items | ||
| assert items, "This function does not support empty tuples" |
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Not necessary but would have been marginally helpful
for more information, see https://pre-commit.ci
BobTheBuidler
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hauntsaninja
approved these changes
Dec 6, 2025
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hauntsaninja
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hauntsaninja
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This looks reasonable to me, worth adding a test?
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@BobTheBuidler Thank you for this PR! I confirm that it fixes #20341 From 1bb7a8edae97b976b28a02ea1d78862bca7fdc06 Mon Sep 17 00:00:00 2001
From: "Michael R. Crusoe" <[email protected]>
Date: Sun, 7 Dec 2025 11:03:23 +0100
Subject: [PATCH] added my reduced test case from the original issue
---
mypyc/test-data/run-generators.test | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/mypyc/test-data/run-generators.test b/mypyc/test-data/run-generators.test
index c8e831734..cf1dac7c5 100644
--- a/mypyc/test-data/run-generators.test
+++ b/mypyc/test-data/run-generators.test
@@ -936,3 +936,11 @@ def test_generator_override() -> None:
assert base1_foo(Base1()) == [1]
assert base1_foo(Derived1()) == [2, 3]
assert derived1_foo(Derived1()) == [2, 3]
+
+[case testGeneratorEmptyTuple]
+from collections.abc import Generator
+from typing import Optional, Union
+
+def test_compiledGeneratorEmptyTuple() -> None:
+ jobs: Generator[Optional[str], None, None] = (_ for _ in ())
+ assert list(jobs) == []
--
2.47.3 |
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|
I've just added a test case now, and then I saw your message @mr-c . Thank you! @maintainers should I add his case in as well? |
hauntsaninja
reviewed
Dec 8, 2025
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|
Added |
hauntsaninja
approved these changes
Dec 9, 2025
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|
Thank you @BobTheBuidler @hauntsaninja ! |
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This PR fixes #20341