A constant-FOLDABLE expression array dimension (`[M + 1]`, `[M * N]`,
`[N - M]`, nested `[M + N - 1]`, parenthesised `[(M + 1) * 2]`, mixing
untyped and typed module consts) was wrongly rejected as "not a
compile-time integer constant" even though every operand is
compile-time-known. Attempts 1-3 resolved only a bare named-const dim or
a literal; an expression dim must be EVALUATED, not rejected.
Fix: the shared dim resolver now routes the dimension through a single
constant integer-expression evaluator (`program_index.evalConstIntExpr`)
that folds integer `+ - * / %` and unary negate over literals and
named/typed module consts, recursively (parentheses carry no AST node).
The leaf-name lookup is delegated via `ctx.lookupDimName`, so the
stateful body-lowering path (`Lowering`, which also sees comptime
constants and generic `$N` values) and the stateless registration path
(`type_bridge.StatelessInner`, module consts only) share the EXACT SAME
folding logic and cannot diverge — an expression dim via a type alias
resolves identically to the direct form.
No-fabrication discipline unchanged: a genuinely non-comptime dimension
(runtime local, non-comptime call, unbound name) or arithmetic that
overflows / divides by zero still yields null -> `.unresolved` -> the
same clean compile-halting diagnostic, never a fabricated length.
- examples/0144-types-const-expr-array-dim.sx: every expression form,
direct vs alias, scalar / string / struct element types (fails on the
pre-fix compiler, passes after).
- examples/1129 re-pointed at a genuinely non-const dimension
(`[get()]s64`, a runtime call) so it still proves the stateless
clean-halt (a foldable expression is no longer an error).
- program_index.test.zig: unit test for evalConstIntExpr folding and
clean-halt-on-non-const.
A type alias whose dimension is a named const (`Arr :: [N]T`) resolves its
dimension eagerly during scanDecls pass 1, on the stateless registration path,
which can only read `module_const_map`. Typed consts (`N : s64 : 16`) register
only in pass 2 and a forward-declared untyped const had not registered yet, so
the stateless resolver saw an empty table, printed a non-fatal warning,
fabricated length 0, and continued — yielding a 0-byte alloca, garbage reads,
and a segfault for slice/struct elements.
- scanDecls pass 0 pre-registers every integer-valued module const before any
type alias resolves, so typed, untyped, and forward-referenced consts all
resolve identically.
- Both dim resolvers now share `program_index.moduleConstInt`, so the stateful
body-lowering path and the stateless registration path cannot diverge.
- `resolveArrayLen` returns `?u32`; `resolveCompound` yields `.unresolved` on
null instead of a 0-length array. The stateful path emits a diagnostic; the
alias-registration path surfaces an unresolved alias as a clean compile error
that aborts the build. The Vector lane-count `else => 0` is fixed the same way.
Regressions: examples/0143 (typed-const dim direct + via alias for s64/string/
struct, forward-ref alias, nested) and examples/1129 (an unresolvable computed
dim halts with a clean diagnostic + non-zero exit). Both fail on the pre-fix
compiler (garbage/segfault; warning+exit0) and pass after.
