[Issue 5995] string append negative integer causes segfault

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=5995

--- Comment #12 from Steven Schveighoffer <schveiguy at yahoo.com> ---
(In reply to hsteoh from comment #11)
> Should appending invalid codepoints append the Unicode replacement character
> instead?

I think implicit casting of int to dchar should be invalid altogether. See my
2011 comment.

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