error[E0277]: the trait bound `u32: ~const Plus` is not satisfied
  --> $DIR/call-const-trait-method-fail.rs:27:5
   |
LL |     a.plus(b)
   |     ^ the trait `Plus` is not implemented for `u32`
   |
note: required by a bound in `Plus::plus`
  --> $DIR/call-const-trait-method-fail.rs:5:1
   |
LL | #[const_trait]
   | ^^^^^^^^^^^^^^ required by this bound in `Plus::plus`
LL | pub trait Plus {
LL |     fn plus(self, rhs: Self) -> Self;
   |        ---- required by a bound in this associated function
help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
   |
LL | pub const fn add_u32(a: u32, b: u32) -> u32 where u32: Plus {
   |                                             +++++++++++++++

error: aborting due to 1 previous error

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