Template constraints should introduce identifiers inside their scopes

[HuskyNator]

On Wednesday, 21 September 2022 at 12:18:19 UTC, Quirin Schroll 
wrote:
> They are not semantically the same. The first can be 
> instantiated with any type and conditionally makes an output 
> (it is empty otherwise), the other says it cannot be 
> instantiated unless the arguments have specific properties.

I am aware of the differences when the if statement fails, though 
the intent remains the same.

> There are better ways than a string `mixin` to do this.
I am aware, this is merely an example.

> You want identifiers defined in a constraint to be visible in 
> the body of the template. This is possible in simple cases like 
> yours, but what if the `is` check is nested or negated?

I would presume it to work identically to its behavior inside a 
static if statement.