69dcee88cd
Step 3 of the variadic heterogeneous type packs feature.
`$args[$i]` (with `$i` a literal integer for the first slice)
should resolve to the i-th element type of the active pack
binding in every type position: return types, param types,
local var annotations, fn-pointer type literals, struct fields.
Today the parser hits "expected '{'" at the `$args[<lit>]`
token because the `$<ident>` arm in `parseTypeExpr` only
recognises plain generic names (`$T`, `$T/Eq/Hashable`).
After `<ident>`, an opening `[` is unexpected.
`examples/165-pack-type-position.sx` exercises two type
positions per mono — a return type `-> $args[0]` AND a local
var annotation `second : $args[1] = args[1]` — so the parser
change must cover more than the trailing return arrow. Two
call shapes (`swap_take(42, "ignored")` and `swap_take("first",
99)`) confirm heterogeneous monos pick distinct concrete
types per position.
Cadence shape 2: the expected output is the WORKING output
("42 first"); pre-fix the diff vs the parser-error output
fails. Next commit lands the parser + resolver changes and the
test flips green.
204/204 + 1 expected-failing = 205 total. `zig build test`
green.
40 lines
1.5 KiB
Plaintext
40 lines
1.5 KiB
Plaintext
// Variadic heterogeneous type packs — step 3: `$args[$i]` in
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// type positions.
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//
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// `$args[$i]` resolves to the i-th element type of the active
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// pack binding wherever a type expression is expected:
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// - return type: `-> $args[0]`
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// - local var annotation: `x : $args[1] = ...`
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// - (later: param types, fn-pointer types, struct field types)
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//
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// Today's parser hits "expected '{'" at the `$args[0]` token in
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// the return type position because the `$<ident>` arm only
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// accepts plain generic names; `[<int>]` after the name isn't
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// recognised. This file pins that rejection. Next commit teaches
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// the parser to accept `$<pack>[<int>]` and adds a new
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// `PackIndexTypeExpr` AST node; `resolveTypeWithBindings`
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// consults the active `pack_arg_types` map.
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//
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// The body intentionally exercises TWO positions per mono — the
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// return type AND a local annotation — so the parser change has
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// to cover more than just the trailing return arrow.
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#import "modules/std.sx";
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swap_take :: (..$args) -> $args[0] {
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second : $args[1] = args[1];
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// `second` is bound and typed — confirms the local-annotation
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// path also resolves. The body returns args[0] (statically
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// typed as $args[0]).
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return args[0];
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}
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main :: () -> s32 {
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// Heterogeneous call shapes — each picks a different concrete
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// pair, gets its own mono.
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a : s64 = swap_take(42, "ignored"); // $args[0] = s64, $args[1] = string
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b : string = swap_take("first", 99); // $args[0] = string, $args[1] = s64
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print("{} {}\n", a, b);
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return 0;
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}
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