lab/sx

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agra 1f9f944ca1 fix(ir): exhaustive named-const array dims (0083) + nested slice-literal coercion (0085)

Makes the F0.4 fixes exhaustive across every resolution / nesting path.

0083 — named-const array dimension, stateless paths. Attempt 1 fixed the
stateful resolver (direct local decls, struct fields, params, returns) but the
binding-free registration-time resolver (`type_bridge`, used for type aliases
`Arr :: [N]T` and inline union/enum field types) still resolved a named dim with
a silent `else 0`, so `Arr :: [N]s64; a : Arr` and `union { a: [N]s64 }` were
still miscompiled (garbage / bus error). Thread the module-global const table
(`ProgramIndex.module_const_map`) into `type_bridge` alongside the alias map, so
`StatelessInner.resolveArrayLen` resolves a named module-const dim to the same
length everywhere. The remaining unresolvable case (a computed/comptime dim on
the binding-free path, which the stateful path hard-errors) now bails LOUDLY
instead of fabricating a 0 length.

0085 — nested slice-literal elements. `lowerArrayLiteral` lowered each element
with the element type as target but appended the raw value. A nested `.[...]`
element at a slice element type (`[][]s64`) still lowers to an aggregate array
`[N]T`, so the outer aggregate held raw arrays where slice {ptr,len} headers
were expected — indexing the inner slice read a garbage pointer and segfaulted.
After lowering each element, coerce a same-element array to the slice element
type via the existing `array_to_slice` op. The coercion recurses with the
nesting, so `[][]T` and deeper materialize at every level — local-bound AND
direct-call-argument forms.

Regressions (fail-before/pass-after demonstrated on the pre-fix compiler):
  examples/0140-types-named-const-array-dim.sx — extended with type-alias,
    nested [N][M]T, and union-field named dims (s64 / string / struct elems)
  examples/0142-types-nested-slice-literal-elements.sx — [][]s64 + [][]string,
    local-bound vs direct-arg
  src/ir/type_bridge.test.zig — named-const dim resolves to literal length

Gate: zig build, zig build test, bash tests/run_examples.sh (388 passed).
Issues 0083 and 0085 marked RESOLVED.

2026-06-04 09:06:08 +03:00

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0083 — fixed array with a named-constant dimension is miscompiled

RESOLVED. Root cause: TypeResolver.resolveCompound's array arm resolved the dimension with if (length.data == .int_literal) ... else 0 — a named const (N :: 16) hit the silent else 0, so [N]T became a 0-length / 0-byte array and element access ran out of bounds (garbage for scalars, bus error for slice/pointer/struct elements). Fix: the array arm now delegates the dimension to inner.resolveArrayLen (symmetric with inner.resolveInner for the element type). The stateful Lowering.resolveArrayLen evaluates the dimension as a compile-time integer across the comptime-constant, generic-value, and module-global const tables, and emits a diagnostic (no fabricated length) when it isn't one.

Exhaustive follow-up (attempt 2). The first fix covered every stateful resolution path (direct local decls, struct fields, function params/returns), but the stateless registration-time resolver (type_bridge, used for type aliases Arr :: [N]T and inline union/enum field types) still resolved the named dim with a silent else 0 — so Arr :: [N]s64; a : Arr and union { a: [N]s64 } were still miscompiled. Fix: the module-global const table (ProgramIndex.module_const_map) is now threaded into type_bridge alongside the alias map, so StatelessInner.resolveArrayLen resolves a named module-const dim to the same length everywhere. The remaining unresolvable case (a computed/comptime dimension on the binding-free path) bails LOUDLY instead of fabricating a 0 length. Files: src/ir/type_resolver.zig, src/ir/lower.zig, src/ir/type_bridge.zig. Regression: examples/0140-types-named-const-array-dim.sx (direct + type-alias + nested [N][M]T + union-field dims, s64 / string / struct element types).

Symptom

A fixed array whose dimension is a module-global integer constant (N :: 16; a : [N]T) miscompiles element access: reads/writes compute a wrong address. With s64 elements a[0] returns GARBAGE (silent); with slice/pointer element types ([N]string) it Bus-errors. The identical program with a LITERAL dimension (a : [16]T) is correct. Silent-miscompile class (cf. 0079–0082).

Reproduction

#import "modules/std.sx";
N :: 16;
main :: () { a : [N]s64 = ---; a[0] = 7; print("a0={}\n", a[0]); }

./zig-out/bin/sx run prints a0=8472789232 (garbage); want a0=7. Replacing [N] with [16] prints 7.

Investigation prompt

A fixed-array TYPE whose dimension is a named const (N :: 16; [N]T) resolves to a wrong element stride / array length in codegen — element address computation is wrong (garbage for scalars, bad pointer for slice/pointer elements). Literal dimensions are correct, so the defect is in resolving the array-type DIMENSION from a constant expression (vs a literal) — the dim likely resolves to 0/unknown or the element size is wrong. Look at array-type resolution where the length is a const-expr (type lowering / sizeof / element-stride computation). Fix so a named-const dimension yields the same layout as the literal. Verify with the repro (expect 7) + a [N]string/[N]struct case (no bus error, correct reads), and zig build && zig build test && bash tests/run_examples.sh green.

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0083 — fixed array with a named-constant dimension is miscompiled

Symptom

Reproduction

Investigation prompt

3.2 KiB

Raw Blame History