Adding pure to a function type

[jmh530]

On Thursday, 26 October 2017 at 16:06:28 UTC, jmh530 wrote:
> On Thursday, 26 October 2017 at 15:47:03 UTC, Andrei 
> Alexandrescu wrote:
>>
>> s/less hideous/even more awesome/
>>
>> No need to be testy :o).
>>
>> I noticed there's no way to say "just leave linkage as is". I 
>> tried SetFunctionAttributes!(typeof(&impl), null, 
>> FunctionAttribute.pure_) and 
>> SetFunctionAttributes!(typeof(&impl), "", 
>> FunctionAttribute.pure_) but neither worked. Should I file a 
>> bug?
>>
>>
>> Andrei
>
> How about:
>
> SetFunctionAttributes!(typeof(&impl), functionLinkage!(&impl), 
> FunctionAttribute.pure_)

Or we can just add in additional overloads like:

template SetFunctionAttributes(T, uint attrs)
     if (isFunctionPointer!T || isDelegate!T)
{
     alias SetFunctionAttributes = 
FunctionTypeOf!(SetFunctionAttributes!(T, functionLinkage!T, 
attrs));
}

template SetFunctionAttributes(T, uint attrs)
     if (is(T == function))
{
     alias SetFunctionAttributes = 
FunctionTypeOf!(SetFunctionAttributes!(T*, attrs));
}

template SetFunctionAttributes(T, string linkage)
     if (isFunctionPointer!T || isDelegate!T)
{
     alias SetFunctionAttributes = 
FunctionTypeOf!(SetFunctionAttributes!(T, linkage, 
functionAttributes!T));
}

template SetFunctionAttributes(T, string linkage)
     if (is(T == function))
{
     alias SetFunctionAttributes = 
FunctionTypeOf!(SetFunctionAttributes!(T*, linkage));
}