An immediate issue which could be addressed with further complexity is that for loop desugaring is done very early in Rust's compilation pipeline, way before ty

An immediate issue which could be addressed with further complexity is that for loop desugaring is done very early in Rust's compilation pipeline, way before typing is actually performed. This would also be weird in the case that you have a for loop over some generic iterator, the monomorphized code could vary quite a bit based on what trait your type implements.