Fix false positive when runtime_checkable() is used as a function

mypy/checkexpr.py

@@ -44,6 +44,7 @@
     LITERAL_TYPE,
     REVEAL_LOCALS,
     REVEAL_TYPE,
+    RUNTIME_PROTOCOL_DECOS,
     UNBOUND_IMPORTED,
     ArgKind,
     AssertTypeExpr,
@@ -772,9 +773,16 @@ def check_runtime_protocol_test(self, e: CallExpr) -> None:
                 and tp.is_type_obj()
                 and tp.type_object().is_protocol
                 and not tp.type_object().runtime_protocol
+                and not self._is_runtime_checkable_call(expr)
             ):
                 self.chk.fail(message_registry.RUNTIME_PROTOCOL_EXPECTED, e)
 
+    def _is_runtime_checkable_call(self, expr: Expression) -> bool:
+        """Check if expr is a call to runtime_checkable() wrapping a protocol."""
+        if isinstance(expr, CallExpr) and isinstance(expr.callee, RefExpr):
+            return expr.callee.fullname in RUNTIME_PROTOCOL_DECOS
+        return False
+
     def check_protocol_issubclass(self, e: CallExpr) -> None:
         for expr in mypy.checker.flatten(e.args[1]):
             tp = get_proper_type(self.chk.lookup_type(expr))

test-data/unit/check-protocols.test

@@ -1718,6 +1718,24 @@ if isinstance(x, R):
 [builtins fixtures/isinstance.pyi]
 [typing fixtures/typing-full.pyi]
 
+[case testRuntimeCheckableCalledAsFunctionInIsinstance]
+from typing import Protocol, runtime_checkable
+
+class P(Protocol):
+    def meth(self) -> None:
+        pass
+
+x: object
+
+# runtime_checkable() used as a function call rather than a decorator
+if isinstance(x, runtime_checkable(P)):
+    reveal_type(x)  # N: Revealed type is "__main__.P"
+
+if issubclass(type(x), runtime_checkable(P)):
+    pass
+[builtins fixtures/isinstance.pyi]
+[typing fixtures/typing-full.pyi]
+
 [case testRuntimeIterableProtocolCheck]
 from typing import Iterable, List, Union