error: unconstrained generic constant
  --> $DIR/issue-51892.rs:14:17
   |
LL |     type Type = [u8; std::mem::size_of::<<T as Trait>::Type>()];
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: try adding a `where` bound using this expression: `where [(); std::mem::size_of::<<T as Trait>::Type>()]:`

error: aborting due to previous error