"Error: `TypeInfo` cannot be used with -betterC" on a CTFE function

[Liam McGillivray]

On Sunday, 7 April 2024 at 08:59:55 UTC, Richard (Rikki) Andrew 
Cattermole wrote:
> Unfortunately runtime and CTFE are the same target in the 
> compiler.
>
> So that function is being used for both, and hence uses GC 
> (appending).

Are you sure that string appending was really the problem that 
caused the "TypeInfo" build error? I forgot about this, but I had 
already had a working CTFE function with string appending before 
adding the new one that lead to this error. The symbols that it 
generates could be used in the program compiled with `betterC`.

```
string EnumPrefixes(T)(string oldName, string prefix) {
     string result = "enum " ~ oldName ~ " {\n";
     static foreach(member; __traits(allMembers, T)) {
         result ~= "    " ~ prefix ~ member ~ " = " ~ 
__traits(getMember, T, member).to!int.to!string ~ ",\n";
     }
     return result ~ "}\n";
}
```

The purpose of this was that the enums used by the C library were 
too verbose. I had changed them from things like 
`KeyboardKey.KEY_C` to `Key.C`. I wanted to leave the new enums 
written directly in the module since these were recommended for 
use, but then generate the old ones with CTFE for backwards 
compatibility. The function above was used like 
`mixin(EnumPrefixes!Key("KeyboardKey", "KEY_"));`, and the 
compiler would allow it even when building with `betterC`.