evalComptimeType did `interp.call(...) catch return null`, dropping the
interp's last_bail_detail; callers poisoned to .unresolved with no
diagnostic, so the sentinel reached LLVM emission and panicked
("unresolved type reached LLVM emission"), or hid behind a downstream
cascade.
Clear last_bail_detail before the call; on the catch emit a build-gating
.err at the construction expr's span ("comptime type construction
failed: {detail}", mirroring the #run surfacing in emit_llvm.zig), then
return null to keep the .unresolved poison — now gated by a real message
so no unresolved type reaches emission unannounced.
Empty-variant define now prints 'comptime define(): enum has no
variants' and exits 1 (no panic); make_enum-style computed-slice
failures show their root reason at the construction site.
A failing declare/define (e.g. empty variant list) bails correctly in
the interp, but evalComptimeType swallows last_bail_detail via
`catch return null`; the decl poisons to .unresolved with no diagnostic
and reaches LLVM emission -> panic ("unresolved type reached LLVM
emission"), or hides behind a misleading downstream cascade.
Pre-existing (plain define path), surfaced while starting the make_enum
step. Blocks make_enum's computed (pointer-backed) []EnumVariant slice
decode. Repro + investigation prompt filed; CHECKPOINT-METATYPE marked
BLOCKED. Session paused pending fix per CLAUDE.md IMPASSABLE rule.
