stringify! space adds strange space before :tt symbol

[stevenroose]

Ok sorry for the strange title at first, that was my search query entered in a wrong text box.

So I'm trying to use a macro to use a string and prefix it for usage in a build tag.

But the issue is quite well summed up in this code snippet:

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=9905252de14993fa6a31b3c73c5d0a01

The result is prefix_ doe. Note the space.

Seems to be related to #55658. But in his example he does some much more complex things.

[ExpHP]

Yes. You stringified two identifiers, so the output deliberately contains a space to ensure it contains two identifiers.

If you need to concatenate identifiers, look at the paste crate.

Alternatively, since you're already stringifying:

concat!("prefix_", stringify!($symbol))