Brummel
de674c4d0b
Fix the codegen asymmetry that 15g surfaced. unify_for_subst had an arg-side-only early-return for $u-prefixed synth wildcards. The function's prev-binding recursion can swap a $u from arg into param position when re-unifying a previously-bound type against a fresh arg. Reduced repro: `length [Left 1, Right 10]` — `a` first binds to `Either<Int, $u>`, then the recursive unification against `Either<$u, Int>` lands $u in param-pos[1] and falls through to the catch-all error. Fix is three lines: add a symmetric $u early-return for param side. $u is a synth-only wildcard regardless of which side it ends up on after the prev-binding swap. Doc comment expanded to record the origin and justification. std_either_list_demo refactored: mkleft/mkright workaround helpers removed; the list is now constructed inline by mixing (term-ctor std_either.Either Left 1) and (... Right 10) directly. Same expected output (2, 3, 2, 3); the demo doubles as the 15g-aux regression fixture. Tests: 94/94, unchanged. The fix expanded what compiles without changing observable behaviour for any prior fixture.
31 lines
3.0 KiB
Plaintext
31 lines
3.0 KiB
Plaintext
; Iter 15g (refactored in 15g-aux) — fifth consumer demo. Imports four
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; stdlib modules (std_list, std_either, std_pair, std_either_list);
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; threads a List<Either<Int, Int>> through three combinators that
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; together exercise every monomorphisation site introduced by 15g.
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;
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; The list is constructed inline by mixing `(term-ctor std_either.Either
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; Left ...)` and `(... Right ...)`. Iter 15g surfaced a `unify_for_subst`
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; asymmetry that would have rejected this construction at synth time;
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; 15g-aux fixed it by accepting `$u` synth-wildcards on either side of
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; the param/arg unification (see ailang-codegen/src/lib.rs's
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; `unify_for_subst`). This demo is the regression fixture: if the
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; symmetric early-return is reverted, the inline form below errors out
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; before reaching codegen.
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(module std_either_list_demo
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(import std_list)
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(import std_either)
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(import std_pair)
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(import std_either_list)
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(fn main
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(doc "Drive lefts, rights, and partition_eithers on the same five-element List<Either<Int, Int>> (Left 1, Right 10, Left 2, Right 20, Right 30). Expected output (one per line): 2, 3, 2, 3.")
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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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(seq (do io/print_int (app std_list.length (app std_either_list.lefts (term-ctor std_list.List Cons (term-ctor std_either.Either Left 1) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 10) (term-ctor std_list.List Cons (term-ctor std_either.Either Left 2) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 20) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 30) (term-ctor std_list.List Nil)))))))))
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(seq (do io/print_int (app std_list.length (app std_either_list.rights (term-ctor std_list.List Cons (term-ctor std_either.Either Left 1) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 10) (term-ctor std_list.List Cons (term-ctor std_either.Either Left 2) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 20) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 30) (term-ctor std_list.List Nil)))))))))
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(seq (do io/print_int (app std_list.length (app std_pair.fst (app std_either_list.partition_eithers (term-ctor std_list.List Cons (term-ctor std_either.Either Left 1) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 10) (term-ctor std_list.List Cons (term-ctor std_either.Either Left 2) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 20) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 30) (term-ctor std_list.List Nil))))))))))
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(do io/print_int (app std_list.length (app std_pair.snd (app std_either_list.partition_eithers (term-ctor std_list.List Cons (term-ctor std_either.Either Left 1) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 10) (term-ctor std_list.List Cons (term-ctor std_either.Either Left 2) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 20) (term-ctor std_list.List Cons (term-ctor std_either.Either Right 30) (term-ctor std_list.List Nil))))))))))))))))
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