**TypeScript Version:** master **Code** ``` ts function f<T extends string[] | {}>(a: T) { if (a instanceof Array) { a = a; } } ``` **Expected behavior:** ``` $ node built/local/tsc.js index.ts ``` **Actual behavior:** ``` $ node built/local/tsc.js index.ts index.ts(3,5): error TS2322: Type 'any[]' is not assignable to type 'T'. ```