match / case — structural pattern matching is not parsed

def classify(v):
    match v:
        case 0:
            return "zero"
        case 1 | 2:
            return "small"
        case _:
            return "big"

pascal26:2: error: undefined variable (match)

match is a SOFT keyword in Python — still usable as an ordinary identifier — so it lexes as a name and dies at the use. Visible, not silent.

3 of the neuzelaar corpus's 168 files. Low, and listed so every line of that census has a ticket behind it.

Scope note — pick the subset deliberately

Full structural pattern matching (class patterns, mapping patterns, capture with as, guards) is a large feature. Real code overwhelmingly uses the flat subset: literal patterns, | alternatives, a _ wildcard, and a bare capture name. Landing that subset and REFUSING the rest by name is the right first step — consistent with how the nested-unpacking forms still name themselves rather than mis-parsing (feature-nilpy-starred-and-nested-unpacking).

Do NOT silently treat an unsupported pattern as a wildcard: that turns a missing feature into a wrong answer.

Gate

make test-nilpy + self-host byte-identical, CPython-diffed over the supported subset, plus a {%FAIL}-style refusal test for one unsupported pattern shape.