return when desugaring to closures

[Waldemar Horwat]

Brendan Eich wrote:
> The agreement from the May TC39 meeting was that the declarations  
> implicit (:*) and explicit annotations must normalize to the same  
> type, or there's an error.

That was back when the language had lots of requirements for compile-time expressions, including on all types.  We agreed that that's not part of ES-Harmony, and this condition doesn't make sense when type expressions are evaluated at run time.

    Waldemar