ww: hare-feature batch (_, const, [_]T, ..., size/offset, assert, for-else)

selfhost/cmd/wcc/cgenutil.ww

@@ -619,6 +619,52 @@ fn primsize(name: str) i32 = {
 	return 0;
 };
 
+// letslotsize — slot size for a `let` binding. Like slotsize, but
+// detects `[_]T = arrlit;` (the type-AST has rhs == nil as the
+// length-inferred sentinel) and computes count × element-size from
+// the initialiser. Used by both scanlocals (prologue sizing) and
+// cglet (slot alloc) so they agree on the frame layout.
+export fn letslotsize(c: *cgen, n: *node) i32 = {
+	// `[_]T = arrlit;` — inferred-length array. slotsize would
+	// return elem_size * 1 (treating missing length as 1); intercept
+	// and compute the real count first.
+	if (n.lhs != nil) {
+		if (n.lhs.kind == N_TARRAY) {
+			if (n.lhs.rhs == nil) {
+				if (n.rhs != nil) {
+					if (n.rhs.kind == N_ARRLIT) {
+						let elemn: *node = n.lhs.lhs;
+						let esz: i32 = 8;
+						if (elemn != nil) {
+							if (elemn.kind == N_TNAME) {
+								let ps: i32 = primsize(elemn.str);
+								if (ps > 0) { esz = ps; };
+							};
+						};
+						let cnt: i32 = 0;
+						let e: *node = n.rhs.list;
+						for (e != nil) {
+							let adv: bool = true;
+							if (e.kind == N_FIELD) {
+								if (streq(e.str, "...")) {
+									e = nil;
+									adv = false;
+								};
+							};
+							if (adv) {
+								cnt += 1;
+								e = e.next;
+							};
+						};
+						return esz * cnt;
+					};
+				};
+			};
+		};
+	};
+	return slotsize(c, n.lhs);
+};
+
 fn slotsize(c: *cgen, typn: *node) i32 = {
 	if (typn == nil) { return 8; };
 	let k: i32 = typn.kind;