compiler/rustc_error_codes/src/error_codes/E0741.md

   1 A non-structural-match type was used as the type of a const generic parameter.
   2
   3 Erroneous code example:
   4
   5 ```compile_fail,E0741
   6 #![feature(const_generics)]
   7
   8 struct A;
   9
  10 struct B<const X: A>; // error!
  11 ```
  12
  13 Only structural-match types (that is, types that derive `PartialEq` and `Eq`)
  14 may be used as the types of const generic parameters.
  15
  16 To fix the previous code example, we derive `PartialEq` and `Eq`:
  17
  18 ```
  19 #![feature(const_generics)]
  20
  21 #[derive(PartialEq, Eq)] // We derive both traits here.
  22 struct A;
  23
  24 struct B<const X: A>; // ok!
  25 ```