Fix __getattr__ and operators related infinite recursion (#6655)

Fixes #6579.

mypy/checkexpr.py

@@ -704,8 +704,8 @@ def check_call(self,
         elif isinstance(callee, UnionType):
             return self.check_union_call(callee, args, arg_kinds, arg_names, context, arg_messages)
         elif isinstance(callee, Instance):
-            call_function = analyze_member_access('__call__', callee, context,
-                                                  False, False, False, self.msg,
+            call_function = analyze_member_access('__call__', callee, context, is_lvalue=False,
+                                                  is_super=False, is_operator=True, msg=self.msg,
                                                   original_type=callee, chk=self.chk,
                                                   in_literal_context=self.is_literal_context())
             callable_name = callee.type.fullname() + ".__call__"

mypy/checkmember.py

@@ -332,7 +332,8 @@ def analyze_member_var_access(name: str,
         return analyze_var(name, v, itype, info, mx, implicit=implicit)
     elif isinstance(v, FuncDef):
         assert False, "Did not expect a function"
-    elif not v and name not in ['__getattr__', '__setattr__', '__getattribute__']:
+    elif (not v and name not in ['__getattr__', '__setattr__', '__getattribute__'] and
+          not mx.is_operator):
         if not mx.is_lvalue:
             for method_name in ('__getattribute__', '__getattr__'):
                 method = info.get_method(method_name)

test-data/unit/check-classes.test

@@ -2494,6 +2494,22 @@ b = a.bar
 [out]
 main:9: error: Incompatible types in assignment (expression has type "A", variable has type "B")
 
+[case testGetattrWithGetitem]
+class A:
+    def __getattr__(self, x: str) -> 'A':
+        return A()
+
+a = A()
+a[0]  # E: Value of type "A" is not indexable
+
+[case testGetattrWithCall]
+class A:
+    def __getattr__(self, x: str) -> 'A':
+        return A()
+
+a = A()
+a.y()  # E: "A" not callable
+
 [case testNestedGetattr]
 def foo() -> object:
     def __getattr__() -> None:  # no error because not in a class