[Issue 23607] ICE caused by an invalid pipeline involving std.conv.to!string

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23607

--- Comment #2 from Basile-z <b2.temp at gmx.com> ---
caused by https://github.com/dlang/dmd/pull/13946. 

The PR removed error messages that are expected to be output in
src/dmd/typesem.d:321.
If not output, an assertion fails.

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