[mypyc] allow use of enum.Enum (#13995)

Fixes mypyc/mypyc#896

Author: hauntsaninja

mypyc/irbuild/classdef.py

@@ -482,7 +482,11 @@ def populate_non_ext_bases(builder: IRBuilder, cdef: ClassDef) -> Value:
                 name = "_NamedTuple"
             base = builder.get_module_attr("typing", name, cdef.line)
         else:
-            base = builder.load_global_str(cls.name, cdef.line)
+            cls_module = cls.fullname.rsplit(".", 1)[0]
+            if cls_module == builder.current_module:
+                base = builder.load_global_str(cls.name, cdef.line)
+            else:
+                base = builder.load_module_attr_by_fullname(cls.fullname, cdef.line)
         bases.append(base)
         if cls.fullname in MAGIC_TYPED_DICT_CLASSES:
             # The remaining base classes are synthesized by mypy and should be ignored.

mypyc/test-data/run-classes.test

@@ -263,6 +263,16 @@ class TestEnum(Enum):
 
 assert TestEnum.test() == 3
 
+import enum
+
+class Pokemon(enum.Enum):
+    magikarp = 1
+    squirtle = 2
+    slowbro = 3
+
+assert Pokemon.magikarp.value == 1
+assert Pokemon.squirtle.name == 'squirtle'
+
 [file other.py]
 # Force a multi-module test to make sure we can compile multi-file with
 # non-extension classes