Alias should `push()` extra stack space for blocks.
@@ -2583,7 +2583,8 @@ codegen(codegen_scope *s, node *tree, int val)
genop(s, MKOP_ABx(OP_LOADSYM, cursp(), b));
push();
genop(s, MKOP_A(OP_LOADNIL, cursp()));
- pop_n(3);
+ push();
+ pop_n(4);
genop(s, MKOP_ABC(OP_SEND, cursp(), c, 2));
if (val) {
push();
