Can't merge const enum with namespace

TypeScript Version: nightly (2.5.0-dev.20170628)

Code

enum E {}
namespace E {}

const enum C {}
namespace C {}

Expected behavior:

No error.

Actual behavior:

src/a.ts(5,11): error TS2473: Enum declarations must all be const or non-const.

[ajafff]

If the namespace contains any statement you get another error: Duplicate identifier 'C'.

const enum C {}
namespace C {;}

FWIW I think the behavior is correct in both cases.

[mhegazy]

Duplicate of #17372