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__name__ on a BUILTIN type is unimplemented

Repro

g = str
print(g.__name__)



pxx:     Unhandled exception: AttributeError: 'type' object has no attribute '__name__'
CPython: str

Position-independent — the same error at top level, in a call argument, and as a parameter default, which is what says it is the VALUE and not the context.

The boundary

case result
class W: pass then W.__name__ ok — W
g = W then g.__name__ ok — W
str.__name__ / g = str; g.__name__ AttributeError
def f(c=str): c.__name__ AttributeError (same cause, not the default path)

So a USER class carries __name__ and a BUILTIN type does not: the two are different runtime values — a user class boxes as VT_CLASSREF (its RTTI blob, which has the name), a builtin type as VT_BTYPE (a small type code), and only the first has anywhere to read a name from.

Fix shape (not attempted)

VT_BTYPE's payload is the PYBT_* code, so __name__ is a code→name table lookup on the builtin-type attribute path — the same place PyBoxBuiltinType values are read. Small, and worth checking __qualname__ and repr() of a builtin type at the same time, since they read from the same nothing.

Why the priority is low

It fails LOUDLY with the right exception type, which is the dialect's stated preference over a wrong value, and no corpus wall measured on 2026-08-17 is blocked on it. It is a completeness gap, not a defect that misleads.

Gate

print(str.__name__) prints str, matching CPython, and the user-class rows above keep working.

Log