fix strictGenericNarrowing causing false positive reportUnnecessaryIsInstance errors when narrowing Callable

packages/pyright-internal/src/analyzer/typeUtils.ts

@@ -1090,9 +1090,8 @@ export const shouldUseVarianceForSpecialization = (typeToNarrow: Type, strictGen
     return allSubtypes(
         typeToNarrow,
         (subtype) =>
-            subtype.category !== TypeCategory.Class ||
-            // !ClassType.isSameGenericClass(subtype, narrowToType) ||
-            subtype.shared.typeParams.length === 0
+            (subtype.category !== TypeCategory.Class || subtype.shared.typeParams.length === 0) &&
+            (subtype.category !== TypeCategory.Function || !subtype.priv.isCallableWithTypeArgs)
     );
 };
 

packages/pyright-internal/src/tests/samples/typeNarrowingUsingBounds.py

@@ -1,4 +1,4 @@
-from typing import Any, Never, assert_type, runtime_checkable, Protocol, Iterable, Iterator, MutableMapping, Reversible
+from typing import Any, Never, assert_type, runtime_checkable, Protocol, Iterable, Iterator, MutableMapping, Reversible, Callable
 
 
 class Covariant[T]:
@@ -115,4 +115,18 @@ def _(
     value: str | Foo[str],
 ):
     if isinstance(value, Foo):
-        assert_type(value, Foo[str])
+        assert_type(value, Foo[str])
+
+def _(f: Callable[[], None]):
+    if isinstance(f, staticmethod):
+        # narrowing Callable this way doesn't work so we use the old method.
+        # see https://github.com/DetachHead/basedpyright/issues/905
+        assert_type(f, staticmethod[..., Any])
+
+class CallableProtocol[**P, T](Protocol):
+    def __call__(self, *args: P.args, **kwargs: P.kwargs) -> T: ...
+
+
+def _(f: CallableProtocol[[], None]):
+    if isinstance(f, staticmethod):
+        assert_type(f, staticmethod[[], None])

packages/pyright-internal/src/tests/samples/typeNarrowingUsingBoundsDisabled.py

@@ -1,4 +1,4 @@
-from typing import Any, assert_type, runtime_checkable, Protocol, Iterable, Iterator, MutableMapping, Reversible
+from typing import Any, assert_type, runtime_checkable, Protocol, Iterable, Iterator, MutableMapping, Reversible, Callable
 
 
 class Covariant[T]:
@@ -115,4 +115,18 @@ def _(
     value: str | Foo[str],
 ):
     if isinstance(value, Foo):
-        assert_type(value, Foo[str])
+        assert_type(value, Foo[str])
+
+def _(f: Callable[[], None]):
+    if isinstance(f, staticmethod):
+        # narrowing Callable this way doesn't work so we use the old method.
+        # see https://github.com/DetachHead/basedpyright/issues/905
+        assert_type(f, staticmethod[..., Any])
+
+class CallableProtocol[**P, T](Protocol):
+    def __call__(self, *args: P.args, **kwargs: P.kwargs) -> T: ...
+
+
+def _(f: CallableProtocol[[], None]):
+    if isinstance(f, staticmethod):
+        assert_type(f, staticmethod[[], None])