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[ty] Fix invalid-match-pattern false positives #23338

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Merged
AlexWaygood merged 2 commits into from
Feb 16, 2026
Merged

[ty] Fix invalid-match-pattern false positives #23338

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b11fa6c
[ty] Fix `invalid-match-pattern` false positives
AlexWaygood Feb 16, 2026
bcb0e68
ruffen up those docs
AlexWaygood Feb 16, 2026
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16 changes: 14 additions & 2 deletions crates/ty_python_semantic/resources/mdtest/conditional/match.md
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Original file line number Diff line number Diff line change
Expand Up @@ -444,7 +444,10 @@ then uses `isinstance` to check the match.
If the match pattern is not an instance of `type`, we raise a diagnostic:

```py
def _(val):
from typing import Any
from ty_extensions import Intersection

def _(val, Valid1: type | Any, Valid2: Intersection[type, Any], Valid3: type[Any], Valid4: type[int]):
Invalid1 = "foo"

match val:
Expand All @@ -455,7 +458,16 @@ def _(val):

match val:
# error: [invalid-match-pattern] "`<types.UnionType special-form 'int | str'>` cannot be used in a class pattern because it is not a type"
case Invalid2(): ...
case Invalid2():
pass
case Valid1(): # fine
pass
case Valid2(): # fine
pass
case Valid3(): # fine
pass
case Valid4(): # fine
pass
```

We also raise a diagnostic if the class cannot be used with `isinstance`:
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4 changes: 1 addition & 3 deletions crates/ty_python_semantic/src/types/infer/builder.rs
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Expand Up @@ -5070,9 +5070,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
protocol_class,
);
}
} else if !cls_ty.is_dynamic()
&& !cls_ty.is_subtype_of(self.db(), KnownClass::Type.to_instance(self.db()))
{
} else if !cls_ty.is_assignable_to(self.db(), KnownClass::Type.to_instance(self.db())) {
report_invalid_class_match_pattern(&self.context, &*pattern.cls, cls_ty);
}
}
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