A */** argument in a NilPy constructor call does not parse

• Type: bug (parser) — Track A (compiler/pyparser.inc ctor path).
• Filed by: opus5-frank1, 2026-08-26, while closing [[bug-a-nilpy-double-star-in-a-mixed-argument-list]], whose Gate section names C(**d) as a case to keep green. Measured: it was never green.

Repro

class C:
    def __init__(self, a=1, b=2, c=3):
        self.t = a + b * 10 + c * 100

d = {"b": 5}
print(C(**d).t)

C(7, **d) → 357 and C(*[7, 8], **{"c": 4}) → 487 in CPython; both are the same error in pxx. Not a regression — identical before and after the mixed argument-list fix, which is why it is its own ticket rather than a follow-up.

Why it is not a routing change

Plain calls take the branch at pyparser.inc ≈45340, which now hands the whole argument list to PyStarMixedForwardCall and gets back a PyStarForwardCall(procIdx, list, dict) — a run-time dispatch on len(args) over the arities __init__ accepts.

The ctor path (pyparser.inc:45097) is a separate loop: it parses expressions into its own AN_ARG chain, then allocates the object and calls __init__ with the instance prepended as self. PyStarForwardCall has no receiver parameter, so the forwarding lowering cannot be reused as-is — every arm of its arity dispatch would need the extra leading argument threaded through.

So the work is either (a) give PyStarForwardCall an optional receiver node that every arm prepends, and let the ctor path call it like any other, or (b) allocate the instance into a temp first and route the __init__ call through the ordinary named-callee path, where the star branch already lives. (b) is the normalise-dont-special-case.md move and is probably smaller, but it changes when the object is allocated relative to argument evaluation — which is observable, so it needs its own CPython-oracled rows.

Do not bolt a third star parser onto the ctor loop. The ticket above removed two.

Gate

make compiler/pascal26, then a .npy diffed against CPython covering C(**d), C(7, **d), C(*lst), C(*lst, **d), argument evaluation order relative to allocation, and a class whose __init__ has no defaults, plus the existing test_nilpy_ctor_kwargs / test_nilpy_ctor_star_and_kwargs staying green. Then tools/gate.sh quick.