gh-108682: [Enum] raise TypeError if super().__new__ called in custom __new__ (GH-108704)

When overriding the `__new__` method of an enum, the underlying data type should be created directly; i.e. .

    member = object.__new__(cls)
    member = int.__new__(cls, value)
    member = str.__new__(cls, value)

Calling `super().__new__()` finds the lookup version of `Enum.__new__`, and will now raise an exception when detected.

1 files changed, 7 insertions, 0 deletions

diff --git a/Lib/enum.py b/Lib/enum.py
index 0c985b2c778..4b99e7bda2c 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -856,6 +856,8 @@ class EnumType(type):
                 value = first_enum._generate_next_value_(name, start, count, last_values[:])
                 last_values.append(value)
                 names.append((name, value))
+        if names is None:
+            names = ()
 
         # Here, names is either an iterable of (name, value) or a mapping.
         for item in names:
@@ -1112,6 +1114,11 @@ class Enum(metaclass=EnumType):
             for member in cls._member_map_.values():
                 if member._value_ == value:
                     return member
+        # still not found -- verify that members exist, in-case somebody got here mistakenly
+        # (such as via super when trying to override __new__)
+        if not cls._member_map_:
+            raise TypeError("%r has no members defined" % cls)
+        #
         # still not found -- try _missing_ hook
         try:
             exc = None