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Two-argument super(Cls, self) does not parse

Repro

class A:
    def __init__(self):
        self.v = 1

class B(A):
    def __init__(self):
        super(B, self).__init__()      # error: unexpected token

print(B().v)

Replace the call with super().__init__() and it compiles and prints 1.

form result
super().__init__() — zero-argument ✅
super(B, self).__init__() — two-argument error: unexpected token

Why it is worth filing rather than shrugging at

The two-argument form is not legacy trivia: it is what every library written to run on both Pythons still contains, and it remains valid Python 3. html5lib writes it in every filter — super(Filter, self).__init__(source) — so it is not one file's habit.

Concretely it is now the wall on html5lib/filters/sanitizer.py:769, which is the file the six.moves urllib_parse work existed to unblock. That work landed and moved the file exactly one step, onto this.

The diagnostic is also unhelpful — "unexpected token" with no mention of super — so a reader meets it as a mystery rather than as a missing feature.

Note for whoever takes it

Related but not the same, and worth checking together since they are one concept with two spellings (devdocs/dev/normalise-dont-special-case.md): the zero-argument form already works, so the machinery exists and this is about accepting the explicit arguments and checking they name the enclosing class and self. Do not grow a second path for it.

RESOLVED 2026-08-18 (frank2-7e, Track A+N) — one consumer for both spellings

Reproduced at HEAD (v352 ground, not the pinned v351 the ticket measured) and fixed as the ticket's own note asked: no second path.

There are TWO parse sites, and one of them is in a SHARED file

Worth stating because it is what makes this an A/P-slot job rather than a pure Track N one:

Both did Expect(tkLParen); Expect(tkRParen), i.e. the zero-argument spelling was hard-coded twice. Fixing only the statement site would have left the expression form failing, and fixing them separately would have been the second path the ticket warned about.

The fix

PySuperConsumeArgs (new, pyparser.inc, forward-declared in parser.inc beside PyMakeSuperCall): consumes super's argument list in EITHER spelling. Both sites now call it, and PyMakeSuperCall — the lowering — is untouched. super(Cls, self) means "start the lookup after Cls", which for the enclosing class is exactly what super() already means, so the two spellings genuinely are one concept and now share one implementation.

What is REFUSED, loudly, rather than guessed

super(A, self) inside class B asks to start the lookup ABOVE the enclosing class. That is a different lowering from the inherited call this builds, so it is refused by name instead of being silently treated as super(B, self):

error: Nil Python: super(A, self) inside class B — starting the lookup above the
enclosing class is not supported; super(B, self) and super() are

Same for the shapes around it, each naming super and saying what to write — the ticket's second complaint was that the old diagnostic never mentioned it:

written diagnostic
super(B, cls) only self is supported as the second argument (a classmethod super is not)
super(B) the one-argument form is an unbound super and is not supported
super(type(self), self) the first argument must be a plain class name, not a computed expression
super(1, 2) takes either no arguments or super(<class>, self)

Corpus effect — ONTO the next wall, not past it

Reported past-vs-onto, per the campaign's rule. Zero files compile completely. What moved, HEAD vs pinned v351:

file pinned v351 HEAD
html5lib/filters/sanitizer.py :769 unexpected token :788 undefined variable (yield)
html5lib/filters/lint.py :26 unexpected token :93 undefined variable (yield)

Both cleared the super wall and landed on yield — [[feature-nilpy-yield-outside-a-for-loop]], which is parked with its diagnosis banked. The compounding this ticket and the shim work were ranked for is real, and yield is now the wall in front of the filter pipeline.

Verified

The ticket's repro; the zero-argument form (unchanged); two-argument with arguments; the two-argument form in EXPRESSION position (the second parse site); and the exact html5lib super(WhitespaceFilter, self).__init__(source) shape — all match CPython.

Test: test/test_nilpy_two_argument_super.npy, wired into BOTH test-nilpy and test-core.

Gate: make compiler/pascal26 fixedpoint (converged after 1 round) + tools/gate.sh quick GREEN. Shared file parser.inc touched — A/P slot was declared to the coordinator and held for the whole job.

Log