Is there any good reason why C++ namespaces are "closed" in D?

[Jim Balter]

On Sunday, 29 July 2018 at 03:20:29 UTC, Walter Bright wrote:
> On 7/28/2018 11:18 AM, Manu wrote:
>> Make a PR that implements namespace as a string... I will use 
>> that fork of D forever.
>
> 1. Look how it is mangled on the C++ side. (Use "grep" on the 
> object file.)
>
> 2. Use:
>
>    pragma(mangle, "the mangled name")

People are trying to read C++ header files and convert the 
declarations ... how is that supposed to work? Even if they were 
manually adding declarations, this doesn't sound like a feasible 
approach.