Fix --strict-equality for decorated and aliased __eq__ methods

mypy/checkexpr.py

@@ -28,7 +28,8 @@
     DictionaryComprehension, ComplexExpr, EllipsisExpr, StarExpr, AwaitExpr, YieldExpr,
     YieldFromExpr, TypedDictExpr, PromoteExpr, NewTypeExpr, NamedTupleExpr, TypeVarExpr,
     TypeAliasExpr, BackquoteExpr, EnumCallExpr, TypeAlias, SymbolNode, PlaceholderNode,
-    ARG_POS, ARG_OPT, ARG_NAMED, ARG_STAR, ARG_STAR2, LITERAL_TYPE, REVEAL_TYPE
+    ARG_POS, ARG_OPT, ARG_NAMED, ARG_STAR, ARG_STAR2, LITERAL_TYPE, REVEAL_TYPE,
+    SYMBOL_FUNCBASE_TYPES
 )
 from mypy.literals import literal
 from mypy import nodes
@@ -3931,9 +3932,10 @@ def is_expr_literal_type(node: Expression) -> bool:
 def custom_equality_method(typ: Type) -> bool:
     """Does this type have a custom __eq__() method?"""
     if isinstance(typ, Instance):
-        method = typ.type.get_method('__eq__')
-        if method and method.info:
-            return not method.info.fullname().startswith('builtins.')
+        method = typ.type.get('__eq__')
+        if method and isinstance(method.node, (SYMBOL_FUNCBASE_TYPES, Decorator, Var)):
+            if method.node.info:
+                return not method.node.info.fullname().startswith('builtins.')
         return False
     if isinstance(typ, UnionType):
         return any(custom_equality_method(t) for t in typ.items)

test-data/unit/check-expressions.test

@@ -2217,6 +2217,30 @@ o in exp
 [builtins fixtures/list.pyi]
 [typing fixtures/typing-full.pyi]
 
+[case testCustomEqDecoratedStrictEquality]
+# flags: --strict-equality
+from typing import TypeVar, Callable, Any
+
+F = TypeVar('F', bound=Callable[..., Any])
+
+def deco(f: F) -> F: ...
+
+class Custom:
+    @deco
+    def __eq__(self, other: object) -> bool: ...
+
+Custom() == int()
+[builtins fixtures/bool.pyi]
+
+[case testCustomEqVarStrictEquality]
+# flags: --strict-equality
+
+class Custom:
+    def compare(self, other: object) -> bool: ...
+    __eq__ = compare
+
+Custom() == int()
+[builtins fixtures/bool.pyi]
 
 [case testUnimportedHintAny]
 def f(x: Any) -> None:  # E: Name 'Any' is not defined \