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Avoid duplicate inference results for List[int] #2185

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Merged
merged 1 commit into from
May 19, 2023
Merged

Avoid duplicate inference results for List[int] #2185

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3 changes: 3 additions & 0 deletions astroid/brain/brain_typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -316,6 +316,9 @@ def infer_typing_alias(
# This is an issue in cases where the aliased class implements it,
# but the typing alias isn't subscriptable. E.g., `typing.ByteString` for PY39+
_forbid_class_getitem_access(class_def)

# Avoid re-instantiating this class every time it's seen
node._explicit_inference = lambda node, context: iter([class_def])
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This feels like something we might need to do for a lot of brains.

We us a similar pattern for the enum brain. 😓

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You're quite right. I traced the bulk of the primer noise to needing to do this in other places in the typing brain.

return iter([class_def])


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10 changes: 10 additions & 0 deletions tests/brain/test_brain.py
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Expand Up @@ -650,6 +650,16 @@ def __init__(self, value):
assert isinstance(slots[0], nodes.Const)
assert slots[0].value == "value"

@test_utils.require_version(minver="3.9")
def test_typing_no_duplicates(self):
node = builder.extract_node(
"""
from typing import List
List[int]
"""
)
assert len(node.inferred()) == 1

def test_collections_generic_alias_slots(self):
"""Test slots for a class which is a subclass of a generic alias type."""
node = builder.extract_node(
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