Try more principled way to detect decorated overloads

mypy/semanal.py

@@ -1153,9 +1153,15 @@ def analyze_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
             elif not non_overload_indexes:
                 self.handle_missing_overload_implementation(defn)
 
-        if types and (not isinstance(defn.impl, Decorator) or not defn.impl.decorators):
+        if types and not any(
+            # If some overload items are decorated with other decorators, then
+            # the overload type will be determined during type checking.
+            isinstance(it, Decorator) and len(it.decorators) > 1 for it in defn.items
+        ):
             # TODO: should we enforce decorated overloads consistency somehow?
-            # TODO: how to support decorated overloads in stubs without major slow-down?
+            # Some existing code uses both styles:
+            #   * Put decorator only on implementation, use "effective" types in overloads
+            #   * Put decorator everywhere, use "bare" types in overloads.
             defn.type = Overloaded(types)
             defn.type.line = defn.line
 

test-data/unit/check-newsemanal.test

@@ -3207,8 +3207,7 @@ class User:
         self.first_name = value
 
     def __init__(self, name: str) -> None:
-        self.name = name  # E: Cannot assign to a method \
-                          # E: Cannot determine type of "name"
+        self.name = name  # E: Cannot assign to a method
 
 [case testNewAnalyzerMemberNameMatchesTypedDict]
 from typing import Union, Any