NilPy `break` / `continue`

Type: feature (Track N — Nil-Python frontend; pyparser.inc loop lowering).
Status: done
Found: 2026-07-17, building the NilPy Tk poll loop for the IDE demo — a natural while ...: if ...: break did not compile.
Owner: claude-A-N

Gap

break (and almost certainly continue) are not in the NilPy v1 subset:

def main() -> None:
    i = 0
    while i < 10:
        if i == 3:
            break        # pascal26: error: expected expression
        i = i + 1

break → pascal26:N: error: expected expression. Both are core Python control flow; their absence forces flag-variable workarounds (running = 1; while running == 1: ... running = 0) that are un-Pythonic and error-prone.

Scope

Lower break / continue inside while and for to the IR's existing loop-exit / loop-continue targets (the Pascal frontend already has these — reuse the shared IR loop labels, no new IR op needed → pure Track N frontend work).
Respect nesting: break targets the innermost loop only.
Reject break/continue outside a loop with a clear diagnostic.

Acceptance

The snippet above compiles and prints 0 1 2 (loop exits at 3).
continue skips to the next iteration.
A test/test_nilpy_break_continue.npy regression; make test-nilpy green.

Note

Found alongside a NilPy str + str concatenation gap (also rejected) — that likely belongs to [[feature-nilpy-collections-and-string-methods]]; verify and fold there rather than duplicating.

Measured satisfied 2026-08-09 (by Track B, pinned v252)

for i in range(5):          while i < 6:
    if i == 1: continue         i = i + 1
    if i == 3: break            if i == 2: continue
    print(i)                    if i == 5: break
                                n = n + i

Both loop kinds accept break and continue and produce CPython's answers (0, and n = 8). Evidence only — Track N owns closing this. Found while sweeping Track B's blocked tickets for stale blockers; [[feature-demo-nilpy-ide]] listed this as a blocker.

CLOSED 2026-08-13 — already implemented; the missing piece was the test

Nothing to build. break and continue work in both loop kinds, and the ticket's other two scope lines hold too: nesting targets the innermost loop, and outside a loop each is refused by name (break outside loop / continue outside loop) rather than by a parse error.

Swept beyond the acceptance, all matching CPython: nested for and nested while, break and continue inside a def, while True whose only exit is the break, an exit crossing a try/finally (the finally still runs), continue inside try/except, and for/else — where the else must run only when no break fired, which is the row a naive lowering gets wrong.

test/test_nilpy_break_continue.{npy,expected} (.expected from CPython), wired into test-nilpy, so a later loop-lowering change cannot quietly take this away. Gate: self-host fixedpoint + gate.sh quick GREEN.

Log

2026-08-13 — resolved, commit f1192065b.

NilPy break / continue