Completes issue 0095 (attempt 2). The attempt-1 coerce arm only caught a direct
`const_float` literal, so a non-integral const-folded float EXPRESSION still
truncated silently at a typed local / field default / param default:
M :: 2;
local : s64 = M + 0.5; // → 2 (silent truncation — BUG; now ERRORS)
fld : s64 = M + 0.5; // field default — same
take(x : s64 = M + 0.5) // param default — same
while the typed-CONST site already errored. The integral expression
(`M + 2.0` → 4) folded but the runtime/explicit-cast paths must stay untouched.
Fix:
- New `program_index.evalConstFloatExpr` — the f64 counterpart to
`evalConstIntExpr`, delegating every integer subtree back to it (no parallel
integer logic) and adding only the float literal / unary-negate / `+ - * /`
arms. Pure (no diagnostics, no resolution side effects).
- `Lowering.foldComptimeFloatInit` applies the unified rule to a typed-binding
initializer EXPRESSION: an integral comptime float folds to its `constInt`, a
non-integral one errors, a genuine runtime float / `xx`-cast falls through to
the normal path. It runs `evalConstFloatExpr` FIRST (pure) so a `$pack[i]`
argument is never spuriously type-resolved outside an active binding, then
gates on `isFloat(inferExprType)` so a plain comptime int is left alone.
Wired into the typed-local path, the three struct field-default sites (via a
shared `lowerCoercedDefault`), and the call-argument loop (covers expanded
param defaults).
- One `Lowering.diagNonIntegralNarrow` now emits the narrowing wording at all
five sites (coerce arm, global init, const-expr value, the typed-binding
sites, and the typed-const path). The typed-CONST non-integral diagnostic
therefore reads "cannot implicitly narrow non-integral float …" instead of
the stale "initializer is a float literal / floating-point expression".
Tests: examples/1146 (negative) extended with non-integral const-EXPRESSION
cases at local/field/param; examples/0168 (positive) extended with integral
const-EXPRESSION folds and `xx (M + 0.5)` truncation; examples/1143 reconciled
to the aligned const message (G/BAD/BAD2 stay errors); unit test
`evalConstFloatExpr folds comptime float expressions`. Full gate green (447).
43d44fff75