who start by @, but I can't color them.

The Rust lexer does not detect them as identifiers, its identifier code is:

```c++ static bool IsIdentifierStart(int ch) { return (IsASCII(ch) && (isalpha(ch) || ch == '_')) || !IsASCII(ch); }

/* This isn't quite right for Unicode identifiers */ static bool IsIdentifierContinue(int ch) { return (IsASCII(ch) && (isalnum(ch) || ch == '_')) || !IsASCII(ch); } ```

That is because Rust doesn't allow identifiers to start with `@`

And also, is it possible to define a coloration for every u or i followed by a number ?

That matches the definition of identifier above, so any that exist in one of the keyword lists will be styled for that list, but not any u or i followed by a random number.

but with Rust lexer and tag parser, maybe a ctag problem ?

You are running into the problem with custom types, lexers and tag parsers are intended for a specific language and will only work for a custom type to the extent that your language is the same. Colouring is not a ctags problem, but symbols in the sidebar will be.

Thanks for your very clear answer. So, if I want to color correctly Zig, I have to write a specific lexer. Because it is not a bug but just me who want to do what I can't do, I close it.