2e0b97aaa5
Two follow-on fixes for follow-up #2 (generic pack-fn return). (1) `pack_arg_types` — a new type-only pack binding consulted by `inferExprType` for `<pack_name>[<int_literal>]`. The earlier `pack_arg_nodes`-via-synthesized-idents path lost the type during return-type inference because the synthesized idents ("__pack_args_0" etc.) only resolve once the mono scope is set up — but the inference runs BEFORE scope setup. Now `monomorphizePackFn` installs `pack_arg_types[<pack>] = arg_types` alongside the existing nodes/count maps, and `inferExprType` consults it directly. `foo(..$args) -> $R => args[2]` called as `foo(42, 3.2, "hello")` now correctly returns "hello" (string) — the third element- typed pick threads through inference to the mono ret_ty. (2) `diagPackIndexOOB` — focused diagnostic for `args[<lit>]` where the literal exceeds the pack arity. Pre-fix the substitution returned null and the standard slice-indexing fall-through emitted "unresolved args" — burying the real cause. Now: "pack index 2 out of bounds: 'args' has 1 element" at the index span. Tests: - `examples/160-pack-hetero-ret.sx` — generic `$R` with non- zeroth heterogeneous pick (returns "hello"). - `examples/161-pack-index-oob.sx` — call passes 1 arg but body indexes args[2]; locks in the OOB diagnostic shape. 200/200 example tests + `zig build test` green.
26 lines
840 B
Plaintext
26 lines
840 B
Plaintext
// Variadic heterogeneous type packs — generic `$R` with
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// heterogeneous element pick. `foo(..$args) -> $R => args[2]`
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// returns the THIRD arg's value; the ret type is inferred from
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// the third arg's concrete type per call shape.
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//
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// foo(42, 3.2, "hello") → returns "hello" (string).
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//
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// Exercises:
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// - generic `$R` inference for non-zeroth pack indices.
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// - heterogeneous mixed-type call args binding into distinct
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// types per position (s64, f64, string).
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// - `pack_arg_types` type-only binding for `inferExprType`
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// pre-mono-scope: without it, the synthesized-ident detour
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// loses the type because the scope isn't set up yet during
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// return-type inference.
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#import "modules/std.sx";
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foo :: (..$args) -> $R => args[2];
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main :: () -> s32 {
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a := foo(42, 3.2, "hello");
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print("{}\n", a);
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return 0;
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}
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