Brummel
0e90709a94
Lifts the gate that rejected `(pat-ctor Cons a (pat-ctor Cons b _))`.
Approach: a pure AST → AST pass `ailang_core::desugar::desugar_module`
that flattens nested-Ctor sub-patterns into chains of single-level
matches with let-bound fresh vars and duplicate fall-through. Both
ailang-check and ailang-codegen call the pass at pipeline entry.
Hash-relevant canonical bytes are untouched: the pass runs after
load_module, in memory only. `check`'s returned CheckedModule.symbols
still carries hashes of the original defs so `ail diff` / `ail manifest`
see on-disk identities.
Lit sub-patterns inside a Ctor still rejected — that's the narrower
scope of `nested-ctor-pattern-not-allowed` post-16a; the variant doc
reflects the new meaning.
Fresh-name safety: `$` is a valid ident character in form (A), so
the Desugarer pre-walks every Term::Var / Pattern::Var name into a
BTreeSet and bumps its counter past any user-spelled `$mp_N`.
Already-flat matches go through `is_flat()` and emit identical AST
shapes; every existing fixture produces the same output as before.
New: examples/nested_pat.{ailx,ail.json} prints 30 from
first_two_sum on [10, 20, 30]. e2e test
`nested_ctor_pattern_first_two_sum` guards the path.
Tests: 92/92 (e2e 32→33, ailang-core unit 10→12).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2 lines
1.3 KiB
JSON
2 lines
1.3 KiB
JSON
{"defs":[{"body":{"arms":[{"body":{"args":[{"name":"a","t":"var"},{"name":"b","t":"var"}],"fn":{"name":"+","t":"var"},"t":"app"},"pat":{"ctor":"Cons","fields":[{"name":"a","p":"var"},{"ctor":"Cons","fields":[{"name":"b","p":"var"},{"p":"wild"}],"p":"ctor"}],"p":"ctor"}},{"body":{"lit":{"kind":"int","value":0},"t":"lit"},"pat":{"p":"wild"}}],"scrutinee":{"name":"xs","t":"var"},"t":"match"},"doc":"Sum of the first two elements of an Int list, or 0 if shorter than two.","kind":"fn","name":"first_two_sum","params":["xs"],"type":{"effects":[],"k":"fn","params":[{"args":[{"k":"con","name":"Int"}],"k":"con","name":"std_list.List"}],"ret":{"k":"con","name":"Int"}}},{"body":{"args":[{"args":[{"args":[{"lit":{"kind":"int","value":10},"t":"lit"},{"args":[{"lit":{"kind":"int","value":20},"t":"lit"},{"args":[{"lit":{"kind":"int","value":30},"t":"lit"},{"args":[],"ctor":"Nil","t":"ctor","type":"std_list.List"}],"ctor":"Cons","t":"ctor","type":"std_list.List"}],"ctor":"Cons","t":"ctor","type":"std_list.List"}],"ctor":"Cons","t":"ctor","type":"std_list.List"}],"fn":{"name":"first_two_sum","t":"var"},"t":"app"}],"op":"io/print_int","t":"do"},"kind":"fn","name":"main","params":[],"type":{"effects":["IO"],"k":"fn","params":[],"ret":{"k":"con","name":"Unit"}}}],"imports":[{"module":"std_list"}],"name":"nested_pat","schema":"ailang/v0"}
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