Brummel
1faee673f7
Boss-dispatched fieldtest after audit-mut-local closed. Six AIL
Surface (.ail) fixtures under examples/fieldtest/ exercise the
shipped mut-local surface from a downstream-LLM-author's perspective
(no compiler-source access; DESIGN.md + public examples only).
Positive fixtures all run end-to-end first-try:
- mut-local_1_factorial.ail: straight-line Int accumulator
unroll (5!), prints 120.
- mut-local_2_classify_temp.ail: nested-if assigns into a Unit-
typed mut block, prints classification code.
- mut-local_3_horner.ail: Float mut accumulator for polynomial
evaluation, prints 18.
- mut-local_4_has_small_factor.ail: Bool mut flag via four
if-then-assign checks, prints true.
Negative probes confirm diagnostics fire as documented:
- mut-local_5_lambda_capture_probe.ail: [mut-var-captured-by-lambda].
- mut-local_6_diag_probe.ail: [mut-var-unsupported-type].
Findings:
[friction] F1 — mut without iteration: the accumulator-over-an-
iteration shape never materializes. Without while/for, the LLM-
author still writes a tail-recursive helper (the very pattern
the milestone Goal said mut would replace). examples/mut_counter.ail
illustrates the degeneration. Routing: planner for a while/for
iteration OR tighten DESIGN.md to name the gap honestly.
[friction] F2 — all four mut-related diagnostics emit their
bracketed [code] twice ('error: [code] fn-name: [code] message').
Mechanical bug: the #[error('[code] ...')] Display attributes I
authored in mut.2/mut.4-tidy include the bracketed prefix in the
message body, and the cli-diag-human formatter adds another from
CheckError::code(). Routing: debug (mechanical message-body
cleanup).
[friction] F3 — no surface form to call a zero-arg fn ('(app f)'
rejected at parse with 'expected at least one argument').
Orthogonal to mut-local but surfaced building the closure-factory
probe. Routing: planner for a small tidy iter.
[spec_gap] F4 — DESIGN.md does not name the 'use a tail-rec
helper instead' workaround for the iteration-over-accumulator
shape that mut alone cannot express. Routing: ratify in DESIGN.md
alongside F1's resolution.
[working] W1/W2/W3 — surface reachable on first read; diagnostics
pinpoint cause (mut-assign-out-of-scope even lists available
vars); composes cleanly with if + lambda-without-capture +
final-expression position.
Spec: docs/specs/2026-05-15-fieldtest-mut-local.md (333 lines).
Refs: docs/specs/2026-05-15-mut-local.md, audit-mut-local close
at 8685e96.
40 lines
1.4 KiB
Plaintext
40 lines
1.4 KiB
Plaintext
; Fieldtest mut-local #5 — deliberate probe of the seal-by-construction
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; promise: try to lift a mut-var into a lambda closure.
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;
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; Spec §"Out of scope": "Lambda capture of a mut-var. A lambda body
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; whose free vars include a mut-var of an enclosing Term::Mut is
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; rejected at typecheck with CheckError::MutVarCapturedByLambda."
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;
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; This file is EXPECTED TO FAIL at `ail check` with the
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; `mut-var-captured-by-lambda` diagnostic. The purpose is to probe:
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; - that the diagnostic actually fires
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; - that its rendered text is actionable
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; - that it points at the lambda site, not somewhere else
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;
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; The shape: a mut block declares `count`, builds a closure that would
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; close over `count`, and tries to return the closure. An LLM-author
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; might write this naïvely thinking "I just need a small callback that
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; updates the running count" — exactly the shape the seal forbids.
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(module mut-local_5_lambda_capture_probe
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(fn make_bumper
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(type
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(fn-type
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(params (con Int))
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(ret (fn-type (params (con Int)) (ret (con Int))))))
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(params seed)
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(body
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(mut
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(var count (con Int) 0)
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(assign count seed)
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(lam (params (typed n (con Int)))
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(ret (con Int))
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(body (app + n count))))))
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(fn main
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(type (fn-type (params) (ret (con Unit)) (effects IO)))
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(params)
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(body
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(app print (app (app make_bumper 10) 5)))))
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