A generator called from code written ABOVE its def crashes or loops wrong

Found 2026-10-19 while writing the slot-early regression test. It's pre-existing: 12ddb7d995 does the same.

def early():
    return list(gen(2))

def gen(n):          # also: (n, k=SCALE), (n, xs=None)
    i = 0
    while i < n:
        yield i
        i += 1

print(early())       # CPython: [0, 1]

pxx crashes with no output (SIGSEGV) for gen(n), gen(n, k=SCALE) and gen(n, xs=None). With gen(n, k=3) it prints [0, 1, ..., 10]: n is read wrong. Defining gen above early works. This looks like the generator call or for-in desugar lowering against the shell-pass registration rather than the real one. That was not investigated.