Disallow calling type on Protocol

mypy/checkexpr.py

@@ -1816,10 +1816,14 @@ def check_callable_call(
 
         if (
             callee.is_type_obj()
-            and (len(arg_types) == 1)
+            and len(arg_types) == 1
             and is_equivalent(callee.ret_type, self.named_type("builtins.type"))
         ):
-            callee = callee.copy_modified(ret_type=TypeType.make_normalized(arg_types[0]))
+            proper_arg = get_proper_type(arg_types[0])
+            if isinstance(proper_arg, Instance) and proper_arg.type.is_protocol:
+                callee = callee.copy_modified(ret_type=self.named_type("builtins.type"))
+            else:
+                callee = callee.copy_modified(ret_type=TypeType.make_normalized(arg_types[0]))
 
         if callable_node:
             # Store the inferred callable type.

test-data/unit/check-protocols.test

@@ -4238,6 +4238,35 @@ def g4(a: Input[bytes], b: Output[str]) -> None:
 
 [builtins fixtures/tuple.pyi]
 
+[case testTypeCallOnProtocol]
+from typing import Any, Protocol, cast
+import types
+
+class P(Protocol):
+    def foo(self) -> None: ...
+
+import mod
+
+a: P = mod
+value = type(a)
+reveal_type(value)  # N: Revealed type is "builtins.type"
+reveal_type(value.foo)  # E: "type" has no attribute "foo" \
+                        # N: Revealed type is "Any"
+
+class Namespace: ...
+n = Namespace()
+n.foo = lambda: None  # E: "Namespace" has no attribute "foo"
+
+b: P = cast(Any, n)
+value = type(b)
+reveal_type(value)  # N: Revealed type is "builtins.type"
+reveal_type(value.foo)  # E: "type" has no attribute "foo" \
+                        # N: Revealed type is "Any"
+[file mod.py]
+def foo() -> None: ...
+
+[builtins fixtures/tuple.pyi]
+
 [case testOverloadProtocolSubtyping]
 from typing import Protocol, Self, overload