issue(0140): comptime type-construction bail panics instead of diagnosing

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.

current/CHECKPOINT-METATYPE.md

@@ -74,10 +74,15 @@ in the always-loaded prelude interns them into every module's type table and
 shifts every `.ir` snapshot. On-demand import keeps the prelude clean.
 
 ## Next step
-Pick any (independent):
+**BLOCKED on issue 0140** for the make_enum path (see Known issues). The other
+two are unblocked:
 - **`make_enum(variants: []EnumVariant)`** sx helper over a COMPUTED (non-literal)
   variant list — exercises the interpreter decoding a value-arg slice in `define`
-  (vs. the literal `.[ … ]` the current examples use).
+  (vs. the literal `.[ … ]` the current examples use). **BLOCKED:** a computed
+  (pointer-backed) `[]EnumVariant` slice from a local var / `List` does not decode
+  in `defineEnum`/`decodeVariantElements`, and the resulting interp bail is
+  SWALLOWED (panic / misleading cascade, no root reason) — issue 0140. Fix 0140
+  first so the decode failure surfaces cleanly, THEN implement the slice decode.
 - **Widen `type_info` / `TypeInfo` past `` `enum ``** — struct/tuple variants:
   add `` .`struct ``/`` .`tuple `` to the `TypeInfo` enum in `meta.sx`, teach
   `reflectTypeInfo` to build them, and teach `defineEnum` (→ a `defineType`) to
@@ -87,9 +92,17 @@ Pick any (independent):
   self-reference already rejected — issue 0139.)
 
 ## Known issues
-None. (issue 0139 — by-value self-reference segfault — RESOLVED: `checkInfiniteSize`
-Pass 1g emits a loud "infinitely sized" diagnostic + breaks the cycle; covers
-source + comptime types; `examples/1178` locks it.)
+- **issue 0140 (OPEN) — a failing comptime type construction panics instead of
+  diagnosing.** `evalComptimeType` (`comptime.zig:~457`) swallows the interp's
+  `last_bail_detail` via `catch return null`; callers poison to `.unresolved`
+  with no diagnostic, and `.unresolved` reaches LLVM emission → panic ("unresolved
+  type reached LLVM emission"), or rides behind a misleading downstream cascade.
+  Pre-existing (plain `define` path; surfaced while starting make_enum). Repro:
+  `issues/0140-*.sx`. Blocks the make_enum computed-slice step. **Session paused
+  pending the fix** per the CLAUDE.md IMPASSABLE rule.
+- issue 0139 — by-value self-reference segfault — RESOLVED (`checkInfiniteSize`
+  Pass 1g emits a loud "infinitely sized" diagnostic + breaks the cycle;
+  `examples/1178` locks it).
 
 ## Log
 - **`type_info($T)` reflection done (enum round-trip).** New `BuiltinId.type_info`;