Making AssertError a singleton

[Stefan Koch via Digitalmars-d]

On Tuesday, 13 December 2016 at 18:52:05 UTC, Andrei Alexandrescu 
wrote:
> * People have noticed that certain simple uses of D trigger 
> calls into druntime that are not quite justified. For example, 
> assigning an array of int to another array of int issues a call 
> into a function that uses dynamic introspection (!) to copy any 
> array into any other array. A template present in object.d 
> would trivially do this using introspection to boil down to 
> memcpy.

I am in favor of templatizing more of druntime.
But please keep those templates simple.
I have noticed severe code-bloat at ctfe, and worse when 
ctfe-codegen miscompiles those templates,
there in way to know why!

It will work fine if the bodys are
- very simple (C-subset of D)
- use static if moderately
- please minimize the use of constraints they are wired when it 
comes to ctfe interaction