导入typescript模块提示 TS2306:File 'XXXX/xxxx/xxxx' is not a module

错误提示：
TS2306:File '/Users/user1/xxxx/pages/repomarket/mod1.ts' is not a module.

代码片段如下：

//page1.vue  
<script lang="ts">  
    import Vue from 'vue';  
    import {test1, test2} from './mod1';  
    export default Vue.extend({  
        data() {  
            return {  
                title: 'product-list',  
            };  
        }  
    })  
</script>

同目录下mod1.vue

function test1 (num: number): number{  
    return num + 1;  
}  

function test2(name: string): string{  
    return 'hello ' + name;   
}  

export {  
    test1,  
    test2  
}