Remove unwrap from get_vtable

This avoids ICE on issue rust-lang#97381 I think the bug is a bit deeper though, it compiles fine when `v` is `&v` which makes me think `Deref` is causing some issue with borrowck but it's fine I guess since this thing crashes since `nightly-2020-09-17` 😅

…s, r=RalfJung,JakobDegen

Preserve unused pointer to address casts

Fixes rust-lang#97421.

cc `@RalfJung`

…ywiser

Recover `import` instead of `use` in item

When we definitely don't have a macro invocation (i.e. when we don't have `import ::`), then it's more productive to parse `import` as if it was incorrectly mistaken for `use`.

Not sure if this needs to be a verbose suggestion, but it renders strangely when it's not verbose:
```
error: expected item, found `import`
 --> /home/michael/test.rs:1:1
  |
1 | import std::{io::{self, Write}, rc::Rc};
  | ^^^^^^ help: items are imported using the `use` keyword: `use`
```

Happy to change it to `span_suggestion` instead of `span_suggestion_verbose` though.

Fixes rust-lang#97788

…-arm, r=estebank

Recover missing comma after match arm

If we're missing a comma after a match arm expression, try parsing another pattern and a following `=>`. If we find both of those, then recover by suggesting to insert a `,`.

Fixes rust-lang#80112

Use repr(C) when depending on struct layout in ptr tests

The test depends on the layout of this struct `Pair`, so it should use `repr(C)` instead of the default `repr(Rust)`.