This is different though. Async colors functions, so once you’ve got something that has an async interface, you either go async too, or have to do shenigans to

This is different though. Async colors functions, so once you’ve got something that has an async interface, you either go async too, or have to do shenigans to use it in a blocking way. GATs will just let library authors make more flexible interfaces. If there’s anything to worry about then that may be compile times of complex codebases. I haven’t measured anything but just as a rule of thumb more generic code means longer compile times in Rust-land.