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wcc: forrange bindings get a per-loop scope; dup binders reject

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The TODO(#11) silent-accept of `for (let (a, a) .. xs)` rested on a
stale premise -- resolvewalk has per-block scopes since #53 and IS
the live w6c_ww checker pass. Bindings now install in a per-LOOP
scope (the N_MCASE pattern), so a duplicate name within one pattern
errs "redeclared in same scope" (cstage parity via stamptuplebinds'
scopedefine-nil check) while sequential same-name loops stay legal.
kwtab restores its stated alphabetical order (`import` before `is`,
both stages, kinds swapped in lockstep with names).
This commit is contained in:
Hojun-Cho
2026-08-09 01:59:33 +09:00
parent 411515a83b
commit 999b110001
5 changed files with 45 additions and 20 deletions
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36
selfhost/cmd/wcc/check.ww
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@@ -443,7 +443,19 @@ fn stamptuplebinds(c: *checker, binds: *syntax.node, elems: *syntax.node,
let bnm: str = b.str;
if (bnm.len > 0) {
checkmoduleshadow(c, bnm, what);
syntax.scopedefine(c.cur, bnm, syntax.skind.SK_VAR, nil, b);
// first registration wins; a nil return is a
// same-scope duplicate — `let (a, a) = ..` /
// `for (let (a, a) .. xs)`. Mirrors cstage
// scope_define == NULL → "redeclared".
let ds: *syntax.sym = syntax.scopedefine(c.cur, bnm, syntax.skind.SK_VAR, nil, b);
if (ds == nil) {
cerr("error: ");
cerr(what);
cerr(" '");
cerr(bnm);
cerr("' redeclared in same scope\n");
c.errs += 1;
};
};
};
if (b.type_ == nil) {
@@ -550,17 +562,17 @@ fn resolvewalk(c: *checker, n: *syntax.node) void = {
// `for (let x .. slice) body` / `for (let (a, b) .. slice) body` —
// each binding name becomes a fresh local. Walk the slice expr first
// so its idents resolve before the bindings shadow anything, then
// install bindings and walk the body/else.
//
// TODO(#11): cstage check.c (post-#32) errors `binding '%s'
// redeclared in same scope` when the tuple-pattern lists the same
// name twice (`for (let (a, a) .. xs)`). Wwstage's resolvewalk has
// no per-block scope (see resolvefnbody's docstring) and is used
// only by wwdump_ww as a diagnostic, so silent-accept here avoids
// false-positives on legal cross-block shadow until #11 adds the
// scoping infrastructure.
// install bindings and walk the body/else. The bindings live in a
// per-LOOP scope (the N_MCASE pattern): sequential same-name loops
// each rebind fresh, and a duplicate name WITHIN one pattern
// (`for (let (a, a) .. xs)`) now errs via stamptuplebinds' dup
// check — the old TODO(#11) silent-accept rested on a stale
// premise (resolvewalk HAS block scopes since #53 and IS the live
// w6c_ww checker pass).
if (k == syntax.nkind.N_FORRANGE) {
if (n.lhs != nil) { resolvewalk(c, n.lhs); };
let frouter: *syntax.scope = c.cur;
c.cur = syntax.newscope(frouter);
if (n.list != nil) {
// Tuple destructure `for (let (a,b) .. xs)`: peel the
// iterable's element type and distribute its tuple
@@ -628,10 +640,12 @@ fn resolvewalk(c: *checker, n: *syntax.node) void = {
};
// `break`/`continue` in the body target this loop; the `else`
// block runs at normal cond-false exit (skipped by break) and
// targets an ENCLOSING loop. Mirrors cstage cmd/wcc/check.c:2494.
// targets an ENCLOSING loop — outside the loop scope, like
// cstage's saved-scope restore. Mirrors cmd/wcc/check.c:2494.
c.loops += 1;
if (n.body != nil) { resolvewalk(c, n.body); };
c.loops -= 1;
c.cur = frouter;
if (n.els != nil) { resolvewalk(c, n.els); };
return;
};