Let issubclass narrow Any

Fixes #10680

Author: hauntsaninja

mypy/checker.py

@@ -7860,7 +7860,6 @@ def push_type_map(self, type_map: TypeMap, *, from_assignment: bool = True) -> N
     def infer_issubclass_maps(self, node: CallExpr, expr: Expression) -> tuple[TypeMap, TypeMap]:
         """Infer type restrictions for an expression in issubclass call."""
         vartype = self.lookup_type(expr)
-        type = self.get_isinstance_type(node.args[1])
         if isinstance(vartype, TypeVarType):
             vartype = vartype.upper_bound
         vartype = get_proper_type(vartype)
@@ -7876,13 +7875,16 @@ def infer_issubclass_maps(self, node: CallExpr, expr: Expression) -> tuple[TypeM
             vartype = UnionType(union_list)
         elif isinstance(vartype, TypeType):
             vartype = vartype.item
+        elif isinstance(vartype, AnyType):
+            pass
         elif isinstance(vartype, Instance) and vartype.type.is_metaclass():
             vartype = self.named_type("builtins.object")
         else:
-            # Any other object whose type we don't know precisely
-            # for example, Any or a custom metaclass.
-            return {}, {}  # unknown type
-        yes_type, no_type = self.conditional_types_with_intersection(vartype, type, expr)
+            # Any other object which isn't a type
+            return {}, {}
+
+        issubclass_type = self.get_isinstance_type(node.args[1])
+        yes_type, no_type = self.conditional_types_with_intersection(vartype, issubclass_type, expr)
         yes_map, no_map = conditional_types_to_typemaps(expr, yes_type, no_type)
         yes_map, no_map = map(convert_to_typetype, (yes_map, no_map))
         return yes_map, no_map

test-data/unit/check-isinstance.test

@@ -1867,6 +1867,25 @@ def directed_meet(cls0: ClassT, cls1: ClassT) -> ClassT | None:
     return None
 [builtins fixtures/isinstancelist.pyi]
 
+[case testIssubclassAny]
+# flags: --warn-unreachable
+from typing import Any
+
+def f1(x: Any) -> None:
+    if issubclass(x, int):
+        reveal_type(x)  # N: Revealed type is "type[builtins.int]"
+    else:
+        reveal_type(x)  # N: Revealed type is "Any"
+    reveal_type(x)  # N: Revealed type is "Any"
+
+def f2(x: Any) -> None:
+    if issubclass(x, list):
+        reveal_type(x)  # N: Revealed type is "type[builtins.list[Any]]"
+    else:
+        reveal_type(x)  # N: Revealed type is "Any"
+    reveal_type(x)  # N: Revealed type is "Any"
+[builtins fixtures/isinstancelist.pyi]
+
 [case testIsinstanceTypeArgs]
 # flags: --warn-unreachable
 from typing import Iterable, TypeVar