Include ambiguous in UninhabitedType.__eq__

Author: sterliakov

mypy/types.py

@@ -1236,10 +1236,10 @@ def accept(self, visitor: TypeVisitor[T]) -> T:
         return visitor.visit_uninhabited_type(self)
 
     def __hash__(self) -> int:
-        return hash(UninhabitedType)
+        return hash((UninhabitedType, self.ambiguous))
 
     def __eq__(self, other: object) -> bool:
-        return isinstance(other, UninhabitedType)
+        return isinstance(other, UninhabitedType) and other.ambiguous == self.ambiguous
 
     def serialize(self) -> JsonDict:
         return {".class": "UninhabitedType"}

test-data/unit/check-generic-subtyping.test

@@ -753,6 +753,20 @@ s, s = Nums() # E: Incompatible types in assignment (expression has type "int",
 [builtins fixtures/for.pyi]
 [out]
 
+[case testUninhabitedCacheChecksAmbiguous]
+# https://github.com/python/mypy/issues/19641
+from typing import Mapping, Never, TypeVar
+
+M = TypeVar("M", bound=Mapping[str,object])
+
+def get(arg: M, /) -> M:
+    return arg
+
+get({})
+
+def upcast(d: dict[Never, Never]) -> Mapping[str, object]:
+    return d  # E: Incompatible return value type (got "dict[Never, Never]", expected "Mapping[str, object]")
+[builtins fixtures/dict.pyi]
 
 -- Variance
 -- --------