[Issue 24688] Parameter by-value keeps const (only in templates)

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24688

--- Comment #5 from Dominikus Dittes Scherkl <dominikus at scherkl.de> ---
of course I meant 'cast(T)x', as there is no parameter 'n'.
This is not only boilerplate, you also have to be careful with the parameter
names, as this now occurs three times instead of one time.
Really, I hate this.

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