stage1 整理代码 修复错误

stage1/spl_stmt.c

@@ -991,7 +991,20 @@ void spl_parse_stmt(spl_comp_t *ctx) {
     case TOK_LINE_COMMENT:
         advance(ctx);
         break;
-    case TOK_AT:    /* @extern(...) */
+    case TOK_AT: { /* @extern(...) or @dbg/@@sizeof expression */
+        usize saved = ctx->tok_idx;
+        advance(ctx); /* @ */
+        skip_nl(ctx);
+        spl_tok_t *t = peek(ctx);
+        if (t && t->type == KW_EXTERN) {
+            ctx->tok_idx = saved;
+            parse_extern_decl(ctx);
+        } else {
+            ctx->tok_idx = saved;
+            parse_expr_stmt(ctx);
+        }
+        break;
+    }
     case TOK_SHARP: /* #[extern(...)] (legacy) */
         parse_extern_decl(ctx);
         break;