more precise type narrowing

Author: randolf-scholz

mypy/checkpattern.py

@@ -559,10 +559,12 @@ def visit_class_pattern(self, o: ClassPattern) -> PatternType:
             and type_info.type is not None
             and type_info.fullname == "typing.Callable"
         ):
-            # Consider as `Callable[..., Any]`
+            # Create a `Callable[..., Any]`
             fallback = self.chk.named_type("builtins.function")
             any_type = AnyType(TypeOfAny.unannotated)
-            typ = callable_with_ellipsis(any_type, any_type, fallback)
+            fn_type = callable_with_ellipsis(any_type, ret_type=any_type, fallback=fallback)
+            # if typ is itself callable, use its own type, otherwise Callable[..,, Any]
+            typ = current_type if is_subtype(current_type, fn_type) else fn_type
         else:
             if isinstance(type_info, Var) and type_info.type is not None:
                 name = type_info.type.str_with_options(self.options)

test-data/unit/check-python310.test

@@ -1078,6 +1078,13 @@ match x:
     case Callable() as fn:
         reveal_type(fn)  # N: Revealed type is "def (*Any, **Any) -> Any"
 
+def int_fun(x: int) -> int: return x+1
+
+match int_fun:
+    case Callable() as fn:
+        reveal_type(fn)  # N: Revealed type is "def (x: builtins.int) -> builtins.int"
+
+
 [case testMatchClassPatternNestedGenerics]
 # From cpython test_patma.py
 x = [[{0: 0}]]