TypeScript Version: nightly (2.5.0-dev.20170615)

Code

(not legal JSDoc syntax, but that shouldn't matter in TypeScript code)

/**
 * @type {{foo: (function(string, string): string)}}
 */
const x = { foo: (a, b) => a + b };

Expected behavior:

No error.

Actual behavior:

src/a.ts(2,27): error TS2300: Duplicate identifier 'string'.
src/a.ts(2,35): error TS2300: Duplicate identifier 'string'.