Auto merge of #86965 - sexxi-goose:rfc2229-improve-lint, r=nikomatsakis,lqd

Improves migrations lint for RFC2229

This PR improves the current disjoint capture migration lint by providing more information on why drop order or auto trait implementation for a closure is impacted by the use of the new feature.

The drop order migration lint will now look something like this:
```
error: changes to closure capture in Rust 2021 will affect drop order
  --> $DIR/significant_drop.rs:163:21
   |
LL |             let c = || {
   |                     ^^
...
LL |                 tuple.0;
   |                 ------- in Rust 2018, closure captures all of `tuple`, but in Rust 2021, it only captures `tuple.0`
...
LL |         }
   |         - in Rust 2018, `tuple` would be dropped here, but in Rust 2021, only `tuple.0` would be dropped here alongside the closure
```

The auto trait migration lint will now look something like this:
```
error: changes to closure capture in Rust 2021 will affect `Send` trait implementation for closure
  --> $DIR/auto_traits.rs:14:19
   |
LL |     thread::spawn(move || unsafe {
   |                   ^^^^^^^^^^^^^^ in Rust 2018, this closure would implement `Send` as `fptr` implements `Send`, but in Rust 2021, this closure would no longer implement `Send` as `fptr.0` does not implement `Send`
...
LL |         *fptr.0 = 20;
   |         ------- in Rust 2018, closure captures all of `fptr`, but in Rust 2021, it only captures `fptr.0`
```

r? `@nikomatsakis`

Closes https://github.com/rust-lang/project-rfc-2229/issues/54

0 files changed, 0 insertions, 0 deletions