Hojun-Cho 41a82021a3 wcc: ? error-subset propagation typecheck + tag remap ...

`expr?` previously did a brain-dead RET through whatever AX/DX/CX
held — only safe when operand and enclosing fn had identical variant
ordering. Tests relied on that alignment by construction.

Now:
- Typecheck: each non-first variant of operand must appear as a
  variant of the enclosing fn's return tagged union. Enclosing must
  itself be tagged (a non-tagged return has no slot for errors to
  land in).
- Cgen: on tag != 0, walk operand's error variants and emit a
  conditional tag remap (cmp/jne/mov/jmp) for any whose index in
  enclosing differs from operand's. Identity cases emit nothing,
  so same-shape operands cost zero extra instructions.

Selfhost cgen doesn't implement N_TRYPROP at all (no selfhost source
uses `?`); byte-identity tests still pass.

One existing e2e row used `?` with main returning i32 — relied on
the old loose semantics. Switched to `!` (abort-on-error); it was
exercising success-unwrap, not propagation.

2026-05-12 01:40:02 +09:00

5.8 KiB

Raw Blame History

View Raw