Template argument deduction not working with template specialization

[Steven Schveighoffer]

On 1/17/21 11:22 AM, Paul wrote:
> While trying to use template specializations I noticed the argument 
> deductions do not yield the same version as the ones yielded when being 
> explicit.
> Example:
> 
>> uint a = 1;
>> uint[] b = [2];
>> TFoo(a);
>> TFoo!(uint[])(b);
> 
>> void TFoo(T)(T a) {
>>     pragma(msg, "T: " ~ T.stringof);
>> }
>>
>> void TFoo(T : T[])(T[] a) {
>>     pragma(msg, "T[]: " ~ T.stringof);
>> }
> 
> I noticed that an automatically deduced TFoo call always yields the 
> first, while TFoo!(uint[]) yields the array version if present, and 
> defaults to the first elsewise.
> 
> Am I incorrect in expecting the same behavior when (ab)using argument 
> deduction or does my usage make sense? I tried searching for this 
> combination (deduction & specialization) but couldn't find another forum 
> post / documentation example.

I've always hated that aspect of specialization. I don't really 
understand why it's valid (how can T be T[]?)

This works:

void TFoo(T : U[], U)(T a)

-Steve