error[E0599]: no method named `get_a` found for reference `&Self` in the current scope
  --> $DIR/constrain-trait.rs:16:31
   |
LL |         println!("{:?}", self.get_a());
   |                               ^^^^^ method not found in `&Self`
   |
   = help: items from traits can only be used if the type parameter is bounded by the trait
help: the following trait defines an item `get_a`, perhaps you need to add another supertrait for it:
   |
LL | trait UseString: std::fmt::Debug + GetString {
   |                                  +++++++++++

error[E0599]: no method named `get_a` found for reference `&Self` in the current scope
  --> $DIR/constrain-trait.rs:22:31
   |
LL |         println!("{:?}", self.get_a());
   |                               ^^^^^ method not found in `&Self`
   |
   = help: items from traits can only be used if the type parameter is bounded by the trait
help: the following trait defines an item `get_a`, perhaps you need to add a supertrait for it:
   |
LL | trait UseString2: GetString {
   |                 +++++++++++

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0599`.