`match (e) { ... }` can now sit in expression position, with each
arm using `yield expr;` to produce the match's value:
let v = match (r) {
case let n: i32 => yield n + 1;
case let s: str => yield s.len: i32 + 100;
};
TK_YIELD keyword + N_YIELD AST node, both appended at the tail of
their enums to keep prior numeric values byte-stable for the
wwdump-diff gates.
Checker: cexpr for N_MATCH walks each arm's body looking for the
first N_YIELD; the match's type is the unified yield type (or
ty_void if no yield, preserving the statement-form semantics).
Mismatched arm yields are flagged.
Cgen: a yield-target stack (separate from the loop break stack)
holds each enclosing match's end label. N_YIELD evaluates its
expression into AX (and BX for str) and JMPs to the topmost entry.
cgmatch pushes its end label on entry and pops on exit.
Selfhost mirror: lib/ww/lex/tok.ww kwtab+name, lib/ww/ast.ww
N_YIELD def+print, lib/ww/parse/stmt.ww yield-stmt; selfhost cgen
adds a yieldbuf to the cgen struct and a cgyield helper. Verified
end-to-end: a yield-using program compiled via the wwstage cgen
matches the C-cgen build's exit code.
C-cgen-side nullable folding landed in f4efaac. This commit catches
the selfhost cgen up so a wwstage-compiled binary produces the same
ABI for `(*T | void)`.
- cgenutil: isnullabletype(), nullableptrtag() helpers shaped to
the selfhost cgen's AST-only world view (it doesn't carry a Type
with a .nullable flag — it walks N_TTAGGED node lists). slotsize
returns 8 for nullable.
- cgenexpr cgmatch: nullable arm uses pointer-vs-null discriminator
and binds only the *T case (void has size 0).
- cgenstmt cglet: nullable target spills only AX (no tag word, no
value-word DX/CX).
- cgenstmt cgreturn: nullable return passes AX through with no
shuffle; bare `return;` emits AX = 0 (void encoding).
Verified end-to-end: a fn returning `(*i32 | void)` compiled by the
wwstage cgen produces the same exit code as the C-cgen build. The
995 fixed-point gate stays green — no selfhost source uses nullable
yet, so the existing tagged paths are still byte-identical.
Selfhost parser (lib/ww/parse/expr.ww) recognises postfix `?` and
`!` at the same level as `as`/`is`/`:`. Selfhost cgen
(selfhost/cmd/wcc/cgenexpr.ww) emits matching code: cmp AX against
the success tag (0 in legacy mode), branch over the propagate /
abort path, then unwrap (DX → AX, CX → BX for str). Mirrors the C
cgen but without the tag-remap loop — none of the selfhost code
that uses `?` today needs cross-shape remapping.
lib/ww/lex/lex.ww \\x escape handling switched from 5-line match
blocks to one-liners: ascii.digitval(c: rune)!. Both digits are
already validated by isxdigit above; the void variant is
unreachable, so `!` collapses correctly. 995 fixed-point gate
verifies the selfhost cgen produces the same `!` codegen as C cgen.
`type invalid = i32` (payload: byte index of first bad rune; mirrors
Hare's strconv::invalid = !size) and `type overflow = void` (Hare's
overflow = !void). stoi64/stou64 now return these instead of the
str-error placeholder. atoi64 dropped — lib/CLAUDE.md says graduate
in one go, don't keep both shapes around.
To produce the void variant payload, `void` is now a real
expression literal (TK_VOID kw, N_VOIDLIT). It evaluates to ty_void;
codegen emits MOVQ $0, AX. Both kinds are appended at the tail of
their enums to keep prior numeric values byte-stable for the
wwdump-diff fixtures.
check_file reorder: USE declarations are now installed in pass 1
alongside the type-decl placeholders so dotted type references
(`strconv.invalid` from a typedecl body) resolve. DEF/FN/LET silently
overwrite a USE-occupied slot — matches the old behavior where USE
silently no-op'd when a same-name fn/def existed (the conflict
manifested in selfhost main.combined.ww at `use parse;` colliding
with `export fn parse(a)`).
selfhost mirror: lib/ww/lex/tok.ww kwtab+name; lib/ww/ast.ww
N_VOIDLIT def+print; lib/ww/parse/{expr,parse}.ww TK_VOID handling;
selfhost/cmd/wcc/cgenexpr.ww N_VOIDLIT codegen.
`e is T` returns bool (variant tag == T's index); `e as T` unwraps
to T or exit(1) on mismatch. Postfix, same precedence as `:` cast.
TK_IS / N_TYPETEST / N_TYPEASSERT appended at the tail of their
enums so every prior numeric value stays unchanged — the
990_selfhost wwdump-diff stays byte-clean.
Cgen mirrors the match-case slot-based load (tag at +0, value at
+8/+16), so an N_IDENT tagged-union local works just like a
match scrutinee. Selfhost cgen inlines the slot resolution
because the wwstage cgen drops sign bits on `*i32` output
parameters in this position.
Renames `errors.is` -> `errors.equal` (the only naming collision;
the existing comment already noted it shared shape with
strings.equal/bytes.equal).
