list.reverse() was missing

• Type: bug (missing list method — loud) — Track N
• Found and FIXED: 2026-08-02, by a differential sweep against the CPython oracle.

Measured

xs = [5, 3, 1]
xs.reverse()

error: Nil Python: TPyList has no method reverse

The two forms that build a NEW sequence — reversed(xs) and xs[::-1] — both worked. Only the in-place method was absent, which is the one you use when you mean to mutate.

Fix

TPyList.reverse swapping ends inward (rather than building a copy — that is what "in place" is for), returning Self so the statement lowering can use it as a value node, the same shape sort() and extend() already use.

Verified

test/test_nilpy_list_reverse.npy, wired into make test-nilpy, byte-identical to CPython: the double-reverse identity, empty and single-element lists, a mixed-type list, and confirmation that reversed() / [::-1] still leave the original untouched.

Context

The only gap in that sweep. The rest agreed with CPython: dict assignment, iteration, in, del, .items(), .clear(); list sort/insert/pop/ remove/extend/copy/clear; set literals with duplicates; nested dict-of-list mutation; and a nested-comprehension matrix with element assignment. Container mutation is in good shape.