Closed

Description
TypeScript Version: nightly (2.5.0-dev.20170707)
Code
const x: ReadonlyArray<number> = [0];
x.concat(x);
Expected behavior:
No error.
Actual behavior:
src/a.ts(2,10): error TS2345: Argument of type 'ReadonlyArray<number>' is not assignable to parameter of type 'number | number[]'.
Type 'ReadonlyArray<number>' is not assignable to type 'number[]'.
Property 'push' is missing in type 'ReadonlyArray<number>'.