int plus(int x, int y) {
  return x + y;
}

int main(void) {
  return plus(3, 4);
}

if (equal(tok, "return")) {
    Node *node = new_node(ND_RETURN, tok);
    if (consume(rest, tok->next, ";"))
      return node;

    Node *exp = expr(&tok, tok->next);
    *rest = skip(tok, ";");

    node->lhs = exp;
    return node;
  }

if (tok->kind == TK_IDENT) {
    VarScope *sc = find_var(tok);

    return new_var_node(sc->var, tok);
  }
static Node *new_var_node(Obj *var, Token *tok) {
  Node *node = new_node(ND_VAR, tok);
  node->var = var;
  return node;
}

if (equal(tok, "(")) {
      node = funcall(&tok, tok->next, node);
}
if (ty->kind != TY_STRUCT && ty->kind != TY_UNION)
  exp = new_cast(exp, current_fn->ty->return_ty);

node->lhs = exp;
return node;

Node head = {};
　Node *cur = &head;

while (!equal(tok, ")")) {
    if (cur != &head)
      tok = skip(tok, ",");

    Node *arg = assign(&tok, tok);if (param_ty) {
      if (param_ty->kind != TY_STRUCT && param_ty->kind != TY_UNION)
        arg = new_cast(arg, param_ty);
      param_ty = param_ty->next;
    } else if (arg->ty->kind == TY_FLOAT) {
      // If parameter type is omitted (e.g. in "..."), float
      // arguments are promoted to double.
      arg = new_cast(arg, ty_double);
    }

    cur = cur->next = arg;
}

*rest = skip(tok, ")");

Node *node = new_unary(ND_FUNCALL, fn, tok);
node->func_ty = ty;
node->ty = ty->return_ty; node->args = head.next;

return node;

Node *new_cast(Node *expr, Type *ty) {
  add_type(expr);

  Node *node = calloc(1, sizeof(Node));
  node->kind = ND_CAST;
  node->tok = expr->tok;
  node->lhs = expr;
  node->ty = copy_type(ty);
  return node;
}

static void gen_stmt(Node *node) {
switch (node->kind) {
case ND_RETURN:
    if (node->lhs) {
      gen_expr(node->lhs);
    }　　 println("? jmp .L.return.%s", current_fn->name);
...
}

static void gen_expr(Node *node) {
  switch (node->kind) {
  case ND_FUNCALL: {    int stack_args = push_args(node);
    gen_expr(node->lhs);    for (Node *arg = node->args; arg; arg = arg->next) {　　 　　pop(argreg64[gp++]);
? ? ? println(" mov %%rax, %%r10");? ? ? println("  call *%%r10");
? ? ? println("? add $%d, %%rsp", stack_args * 8);
  }
  case ND_VAR:
    gen_addr(node);return;

  case ND_CAST:
    gen_expr(node->lhs);
    cast(node->lhs->ty, node->ty);
    return;
...
  }
...