Compile time lowercasing/etc of stringify!d idents.

[Manishearth]

In this macro for Servo (PR), I'm taking in an ident, using it as a method name, and later stringify!ing it. Unfortunately, the method name needs to be title case, but the string version needs to be lowercase. I currently get around this by using stringify!($attr).to_ascii_lower().as_slice() but this executes at runtime which is slightly inefficient.

Could we have variants of stringify! that work at compile time?

[Manishearth]

I'm willing to work on this myself, it should be easy enough to add a stringify_lower! and stringify_upper!, or whatever else we need here and here

[SimonSapin]

Rather than special-purpose macros like stringify_lower!(), it may be preferable to have simpler but composable macros: to_ascii_lower!(stringify!()) so that we don’t have to anticipate all possible combinations.

[kmcallister]

We would also use this in the compiler's lint_initializer! macro instead of calling to_ascii_lower.

[Manishearth]

Ah, nice. I'll do that then.

to_ascii_lower!, to_ascii_upper! should be enough, right? Any other macros we may want? I'll try my hand at this tomorrow.

[steveklabnik]

Adding macros would require an RFC nowadays, so I'm giving this a close.

[kmcallister]

Yeah, I think this could be a plugin library.