This includes a change to the way lifetime names are generated. Say we
figure that `[#0, 'a, 'b]` have to be the same lifetimes, then instead
of just generating a new lifetime `'c` like before to replace them, we
would reuse `'a`. This is done so that when the lifetime name comes
from an impl, we don't give something that's completely off, and we
don't have to do much work to figure out where the name came from. For
example, for the following code snippet:
```rust
struct Baz<'x> {
bar: &'x int
}
impl<'x> Baz<'x> {
fn baz1(&self) -> &int {
self.bar
}
}
```
`[#1, 'x]` (where `#1` is BrAnon(1) and refers to lifetime of `&int`)
have to be marked the same lifetime. With the old method, we would
generate a new lifetime `'a` and suggest `fn baz1(&self) -> &'a int`
or `fn baz1<'a>(&self) -> &'a int`, both of which are wrong.
Some types of error are caused by missing lifetime parameter on function
or method declaration. In such cases, this commit generates some
suggestion about what the function declaration could be. This does not
support method declaration yet.
