VM catch frames + expression-form try/catch in the compiler. Uncaught traps
keep byte-for-byte today's surface. log-watcher parse errors 18 -> 7;
corpus 71/0, woc runtest 565/0, wovm unit gates green (both dispatch flavors).
- wob.h: WOP_TRY (A sBx: push catch frame, handler at pc+sBx) / WOP_ENDTRY;
WO_B_ERR_FILL builtin (fills the catch record: 0 code, 1 line, 2 method,
3 msg — the field-order contract with the compiler)
- vm.h/vm.c: catch stack (depth, handler pc, error reg) + the caught error;
vm_unwind takes a stop depth, so a caught trap kills every frame above the
catching one exactly as an uncaught trap would, then releases only what the
try region owned in the catching frame (drop-entry diff against the handler
pc) and resumes at the handler; RET/RET0 drop the catch frames of the frame
they leave; TRAPF resumes instead of returning when the trap was caught
- builtin.c: err_fill allocates the method/msg Texts into the record the
compiler owns, so the pending error never has to outlive the landing
- loader.c: TRY's handler target validated like a jump, error register like
any register operand; err_fill arity
- lexer/token/ast/parser: `try`/`catch` keywords; `try expr catch (e) expr`
and `catch (e) { block }`, newline allowed before `catch`; try binds looser
than every operator, so `try a / b catch (e) 0` catches the division
- types.ml: predeclared `Error` record (merged table only), catch binding,
arm-type agreement reported only when both arms are confidently typed
- owner.ml: analyze_try — the catch arm is an alternate flow join off the
entry state, the error record is an owned handler-scope local
- emit.ml: TRY/body/ENDTRY/JMP + handler prologue (NEW Error, err_fill),
join drops on both arms, `Error` class entry only for programs that catch
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
shoney.arickathil
2bb39d6b6b