Account for non-overlapping unmet trait bounds in suggestion

When a method not found on a type parameter could have been provided by any
of multiple traits, suggest each trait individually, instead of a single
suggestion to restrict the type parameter with *all* of them.

Before:

```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
  --> $DIR/method-on-unbounded-type-param.rs:5:10
   |
LL |     (&a).cmp(&b)
   |          ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `T: Ord`
           which is required by `&T: Ord`
           `&T: Iterator`
           which is required by `&mut &T: Iterator`
           `T: Iterator`
           which is required by `&mut T: Iterator`
help: consider restricting the type parameters to satisfy the trait bounds
   |
LL | fn g<T>(a: T, b: T) -> std::cmp::Ordering where T: Iterator, T: Ord {
   |                                           +++++++++++++++++++++++++
```

After:

```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
  --> $DIR/method-on-unbounded-type-param.rs:5:10
   |
LL |     (&a).cmp(&b)
   |          ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `T: Ord`
           which is required by `&T: Ord`
           `&T: Iterator`
           which is required by `&mut &T: Iterator`
           `T: Iterator`
           which is required by `&mut T: Iterator`
   = help: items from traits can only be used if the type parameter is bounded by the trait
help: the following traits define an item `cmp`, perhaps you need to restrict type parameter `T` with one of them:
   |
LL | fn g<T: Ord>(a: T, b: T) -> std::cmp::Ordering {
   |       +++++
LL | fn g<T: Iterator>(a: T, b: T) -> std::cmp::Ordering {
   |       ++++++++++
```

Fix #108428.

2 files changed, 3 insertions, 3 deletions

diff --git a/tests/ui/box/unit/unique-object-noncopyable.stderr b/tests/ui/box/unit/unique-object-noncopyable.stderr
index 49547872d1a..8ea6edb48a7 100644
--- a/tests/ui/box/unit/unique-object-noncopyable.stderr
+++ b/tests/ui/box/unit/unique-object-noncopyable.stderr
@@ -12,6 +12,9 @@ LL |     let _z = y.clone();
            which is required by `Box<dyn Foo>: Clone`
            `dyn Foo: Clone`
            which is required by `Box<dyn Foo>: Clone`
+   = help: items from traits can only be used if the trait is implemented and in scope
+   = note: the following trait defines an item `clone`, perhaps you need to implement it:
+           candidate #1: `Clone`
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/box/unit/unique-pinned-nocopy.stderr b/tests/ui/box/unit/unique-pinned-nocopy.stderr
index d2bf72249c4..69428604b19 100644
--- a/tests/ui/box/unit/unique-pinned-nocopy.stderr
+++ b/tests/ui/box/unit/unique-pinned-nocopy.stderr
@@ -10,9 +10,6 @@ LL |     let _j = i.clone();
    = note: the following trait bounds were not satisfied:
            `R: Clone`
            which is required by `Box<R>: Clone`
-   = help: items from traits can only be used if the trait is implemented and in scope
-   = note: the following trait defines an item `clone`, perhaps you need to implement it:
-           candidate #1: `Clone`
 help: consider annotating `R` with `#[derive(Clone)]`
    |
 LL + #[derive(Clone)]