Uncallable delegates

[Walter Bright]

I've already acknowledged and filed a bug report with `pure` on delegates:

https://github.com/dlang/dmd/issues/23125

If the `pure` is necessary for your example issue, then that is the problem. If 
it is not necessary, why is it there?

P.S. Fixes to the compile go in the compiler test suite. Use of phobos is not 
allowed in the compiler test suite, as that is both unnecessary and makes it 
unduly difficult to develop the compiler.