Q:

VSCode cannot treat TS file type informations which imported by a short path

import MyClass form '@/MyClass'

Where MyClass.ts is in /User/my/workspace/src/ and @ is a shorthand of /User/my/workspace/src/ in vue-cli 3.0 generated project. 
import MyClass from './MyClass'

was worked fine. 
I think VSCode can't treat '@' in the path, but '@' is a good practice instead of using relative path when the path is long. 

A:

There are many folders in my VSCode workspace inspector, and VSCode may only use the first folder's tsconfig.json.  If your tsconfig.json is not in the first folder, drag the folder to the first and try it again, it worked for me.