Mysterious identifier in std.traits.ParameterStorageClassTuple

[Jens]

On Tuesday, 24 July 2018 at 21:34:34 UTC, arturg wrote:
> On Tuesday, 24 July 2018 at 21:05:05 UTC, Jean-Louis Leroy 
> wrote:
>> What is `PT` here: 
>> https://github.com/dlang/phobos/blob/master/std/traits.d#L1224
>> Where does it come from?
>
> https://dlang.org/spec/expression.html#is_expression
>
> look for
> 6. is ( Type Identifier == TypeSpecialization )

Yes, 6 is right. I was wrong with 7. And 6 also says for 
`__parameters: the parameter sequence of a function, delegate, or 
function pointer. This includes the parameter types, names, and 
default values.` So `PT` refers to the parameter sequence. So not 
only the parameter types.

Jens