-Only structural-match types (that is, types that derive `PartialEq` and `Eq`)
-may be used as the types of const generic parameters.
+A non-structural-match type was used as the type of a const generic parameter.
+
+Erroneous code example:
```compile_fail,E0741
#![feature(const_generics)]
struct B<const X: A>; // error!
```
-To fix this example, we derive `PartialEq` and `Eq`.
+Only structural-match types (that is, types that derive `PartialEq` and `Eq`)
+may be used as the types of const generic parameters.
+
+To fix the previous code example, we derive `PartialEq` and `Eq`:
```
#![feature(const_generics)]
-#[derive(PartialEq, Eq)]
+#[derive(PartialEq, Eq)] // We derive both traits here.
struct A;
struct B<const X: A>; // ok!