TypeScript Version: [email protected]

Search Terms: function arguments grouped union type

Code

I notice that if a union type is grouped with ( and ) it works as a return type but not as an argument type. For example, this does not work:

/**
 * @typedef {function((string|undefined)): (string|undefined)} SomeType
 */

While this does work:

/**
 * @typedef {function(string|undefined): (string|undefined)} SomeType
 */

Expected behavior:

With this tsconfig.json:

{
  "compilerOptions": {
    "target": "ES2017",
    "allowJs": true,
    "checkJs": true,
    "noEmit": true,
    "strict": false,
  },
  "include": [
    "src/**/*.js"
  ]
}

I expected tsc to succeed.

Actual behavior:

src/main.js:2:23 - error TS1138: Parameter declaration expected.

2  * @typedef {function((string|undefined)): (string|undefined)} SomeType
                        ~

src/main.js:2:41 - error TS1005: '}' expected.

2  * @typedef {function((string|undefined)): (string|undefined)} SomeType
                                          ~

Perhaps this is a known limitation. I can remove the parens. But I thought it might also be a parsing bug.