selfhost: port forrange — N_FORRANGE parser + cgen + tuple destructure

selfhost/cmd/wcc/cgendecl.ww

@@ -92,6 +92,33 @@ fn scanlocals(c: *cgen, n: *node) i32 = {
 	// ".sw_<labelseq>" at cgen time — unique per switch — so it must
 	// not dedup. Count it here so the frame SUBQ matches.
 	if (n.kind == nkind.N_SWITCH) { total += 8; };
+	// `for (let x .. s)` allocates two 8B scratch slots — `.rgi_<seq>`
+	// (counter) and `.rgl_<seq>` (length) — plus one slot per binding.
+	// Per-binding sz defaults to 8 (covers scalar primitives + ptrs).
+	// `str` tuple-fields would need 16 — selfhost doesn't yet emit
+	// those, so the simple count tracks C cgen for current fixtures.
+	if (n.kind == nkind.N_FORRANGE) {
+		total += 16;	// .rgi + .rgl scratch
+		if (n.list != nil) {
+			let m: *node = n.list;
+			for (m != nil) {
+				let bnm: str = m.str;
+				if (bnm.len == 0) {
+					total += 8;	// discard binding still gets a slot
+				} else { if (!scanseenmark(c, bnm)) {
+					total += 8;
+				};};
+				m = m.next;
+			};
+		} else {
+			let bnm: str = n.str;
+			if (bnm.len == 0) {
+				total += 8;
+			} else { if (!scanseenmark(c, bnm)) {
+				total += 8;
+			};};
+		};
+	};
 	// Match-arm binding (`case let v: T => ...`) gets a slot too.
 	// Crucially we do NOT dedup these against c.locals: C cgen
 	// handles a match as an expression with a by-value locals copy,