error[E0277]: the trait bound `i32: Tr` is not satisfied
  --> $DIR/issue-84973-2.rs:11:9
   |
LL | fn foo<T: Tr>(i: T) {}
   |           -- required by this bound in `foo`
...
LL |     foo(a);
   |         ^
   |         |
   |         expected an implementor of trait `Tr`
   |         help: consider mutably borrowing here: `&mut a`

error: aborting due to previous error

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