…uggestion

…ercion

But do continue to warn for trait methods.

* Add to 2021 compatibility group
* Set default to Allow

And add tests for some corner cases we have to consider.

Before:

![rustdoc-intra-doc-link-summary-before](https://user-images.githubusercontent.com/1593513/122623069-9d995e80-d04f-11eb-8d46-ec2ec126bb5e.png)

After:

![rustdoc-intra-doc-link-summary](https://user-images.githubusercontent.com/1593513/122623076-a4c06c80-d04f-11eb-967a-f5916871c34b.png)

It's much more complicated than just going through the TyCtxt.

This makes it consistent with rustc_session::Options.

Implement printing of stack traces on LLVM segfaults and aborts

Implement rust-lang#79153

Based on discussion, try to extend the rust_backtrace=1 feature to handle segfault or aborts in the llvm backend

…_lint, r=nikomatsakis

Add `future_prelude_collision` lint

Implements rust-lang#84863. (RFC rust-lang/rfcs#3114 ([rendered](https://github.com/rust-lang/rfcs/blob/master/text/3114-prelude-2021.md))) Not entirely complete but wanted to have my progress decently available while I finish off the last little bits.

Things left to implement:

* [x] UI tests for lints
* [x] Only emit lint for 2015 and 2018 editions
* [ ] Lint name/message bikeshedding
* [x] Implement for `FromIterator` (from best I can tell, the current approach as mentioned from [this comment](rust-lang#84863 (comment)) won't work due to `FromIterator` instances not using dot-call syntax, but if I'm correct about this then that would also need to be fixed for `TryFrom`/`TryInto`)*
* [x] Add to `rust-2021-migration` group? (See rust-lang#85512) (added to `rust-2021-compatibility` group)
* [ ] Link to edition guide in lint docs

*edit: looked into it, `lookup_method` will also not be hit for `TryFrom`/`TryInto` for non-dotcall syntax. If anyone who is more familiar with typecheck knows the equivalent for looking up associated functions, feel free to chime in.

Specify the kind of the item for E0121

Fixes rust-lang#86005

…ark-Simulacrum

Add regression test for issue rust-lang#37508

Add regression test for issue rust-lang#37508

Closes rust-lang#37508

Took this test from rust-lang#37508 and updated the panic handler to the modern standard.

r? `@Mark-Simulacrum`

Mark, I hope you don't me tagging you here. You were involved in the original issue and I hope you might be more comfortable reviewing this.

…oc-link-summary, r=CraftSpider

Resolve intra-doc links in summary desc

Before:

![rustdoc-intra-doc-link-summary-before](https://user-images.githubusercontent.com/1593513/122623069-9d995e80-d04f-11eb-8d46-ec2ec126bb5e.png)

After:

![rustdoc-intra-doc-link-summary](https://user-images.githubusercontent.com/1593513/122623076-a4c06c80-d04f-11eb-967a-f5916871c34b.png)

Cleanup handling of `crate_name` for doctests

- Remove unnecessary reallocation
- Remove unnecessary messing around with `queries` for the crate name; it's simpler and faster to go through the TyCtxt instead
- Rename `cratename` -> `crate_name` for consistency with the rest of the compiler

…eSeulArtichaut

Fix `unused_unsafe` around `await`

Enables `unused_unsafe` lint for `unsafe { future.await }`.

The existing test for this is `unsafe { println!() }`, so I assume that `println!` used to contain compiler-generated unsafe but this is no longer true, and so the existing test is broken. I replaced the test with `unsafe { ...await }`. I believe `await` is currently the only instance of compiler-generated unsafe.

Reverts some parts of rust-lang#85421, but the issue predates that PR.