fix-callable-any-narrowing

Author: Kunal Sali

mypy/checker.py

@@ -6252,17 +6252,19 @@ def conditional_callable_type_map(
         proper_type = get_proper_type(current_type)
         if isinstance(proper_type, AnyType):
             # Narrow Any to a generic callable type to satisfy no-any-return in strict mode.
-            return {
-                expr: CallableType(
-                    [AnyType(TypeOfAny.from_another_any, source_any=proper_type),
-                     AnyType(TypeOfAny.from_another_any, source_any=proper_type)],
-                    [nodes.ARG_STAR, nodes.ARG_STAR2],
-                    [None, None],
-                    ret_type=AnyType(TypeOfAny.from_another_any, source_any=proper_type),
-                    fallback=self.named_type("builtins.function"),
-                    is_ellipsis_args=True,
-                )
-            }, {}
+            # We use a synthesized fallback with fallback_to_any=True to preserve attribute access
+            # (fixing regressions in sympy, pandas, etc. where Any behavior was expected).
+            fallback = self.named_type("builtins.object")
+            if fallback.type.fullname == "builtins.object":
+                # Create a synthesized type that behaves like 'Any' but is an 'Instance'
+                # This satisfies callability checkpoints while preserving dynamic attribute access.
+                cdef = nodes.ClassDef("<any callable>", nodes.Block([]))
+                cdef._fullname = "<any callable>"
+                info = TypeInfo(nodes.SymbolTable(), cdef, "")
+                info.mro = fallback.type.mro
+                info.bases = fallback.type.bases
+                info.fallback_to_any = True
+                return {expr: Instance(info, [])}, {}
 
         callables, uncallables = self.partition_by_callable(current_type, unsound_partition=False)