MemoryAllocator, MemorySubAllocator, etc should not have inherent Debug bounds.

[Lymia]

Though it is good practice in libraries to have Debug impls, applications that define their own allocators may not always want to.

[derekdreery]

You can always to a blank impl of Debug

impl Debug for Something {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "Something")
    }
}

[zakarumych]

I think @Lymia is right. We should not require Debug implementation in traits. But provide it for all structures.