ices/54108.rs: fixed with errors

=== stdout ===
=== stderr ===
error[E0277]: cannot add `<T as SubEncoder>::ActualSize` to `<T as SubEncoder>::ActualSize`
  --> /home/runner/work/glacier/glacier/ices/54108.rs:16:2
   |
4  |     type Size: Add<Output = Self::Size>;
   |                ------------------------ required by this bound in `Encoder::Size`
...
16 |     type Size = <Self as SubEncoder>::ActualSize;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `<T as SubEncoder>::ActualSize + <T as SubEncoder>::ActualSize`
   |
   = help: the trait `Add` is not implemented for `<T as SubEncoder>::ActualSize`
help: consider further restricting the associated type
   |
15 | impl<T> Encoder for T where T: SubEncoder, <T as SubEncoder>::ActualSize: Add {
   |                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
==============

Author: rustbot