TypeScript Version: 3.2.0-dev.20181101
Code
const isMutable = false;
isMutable = true;
Expected behavior:
Cannot assign to 'isMutable' because it is a constant.
Actual behavior:
Cannot assign to 'isMutable' because it is a constant or a read-only property. It's obviously not a property, and the compiler should be able to tell this. Note this is more tricky with namespace N { export const x = 0; }, which is also a property, but I think calling it just "a constant" in that case is fine.