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.
31 lines
1.1 KiB
Plaintext
31 lines
1.1 KiB
Plaintext
; Fieldtest mut-local #1 — factorial 5! via straight-line mut updates.
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;
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; Task: print 5! (= 120) using a `mut` block that names a running
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; product and unrolls five multiplications as straight-line statements.
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; This is the most direct possible use of mut-local: no helper fn, no
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; iteration, just a sequence of in-block updates terminated by reading
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; the var. The LLM-author's mental model of "I want a local accumulator"
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; maps 1:1 onto the surface here.
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;
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; Why this fits mut-local's scope: the milestone supplies only sealed
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; lexically-scoped mutables, with no `while` or `for`. Straight-line
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; unroll is the *only* shape inside one mut block that needs no helper.
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;
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; Expected stdout: 120
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(module mut-local_1_factorial
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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
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(mut
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(var prod (con Int) 1)
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(assign prod (app * prod 1))
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(assign prod (app * prod 2))
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(assign prod (app * prod 3))
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(assign prod (app * prod 4))
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(assign prod (app * prod 5))
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prod)))))
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