package.exports.types field is not working

I made a simple example to test package.exports.types field and the settings read as follow

  "exports": {
    ".": {
      "import": "./build/index.js",
      "require": "./build/index.js",
      "default": "./build/index.js",
      "types": "./build/index.d.ts"
    },
    "./foo": {
      "import": "./build/foo.js",
      "require": "./build/foo.js",
      "default": "./build/foo.js",
      "types": "./build/foo.d.ts"
    },
    "./package.json": "./package.json"
  },

However, when I import this package in the another project, it says

error TS2307: Cannot find module 'exports-test/foo' or its corresponding type declarations.

1 import * as a from 'exports-test/foo'

And it seems that the typescript compiler can't find the type definition file for foo. My typescript version is 4.6.3. And I think I followed every instruction stated in the official document.

What is wrong with my settings? It'd be very helpful if you can share the repository of a working example.