Properly calculate best failure in macro matching
Previously, we used spans. This was not good. Sometimes, the span of the token that failed to match may come from a position later in the file which has been transcribed into a token stream way earlier in the file. If precisely this token fails to match, we think that it was the best match because its span is so high, even though other arms might have gotten further in the token stream.
We now try to properly use the location in the token stream.
This needs a little cleanup as the `best_failure` field is getting out of hand but it should be mostly good to go. I hope I didn't violate too many abstraction boundaries..
Previously, it only checked whether there was _a_ literal at the span of
the first argument, not whether the literal actually matched up. This
caused issues when a proc macro was generating a different literal with
the same span.
This requires an annoying special case for literals ending in `\n`
because otherwise `println` wouldn't give detailed diagnostics anymore
which would be bad.
docs/test: add UI test and long-form error docs for `E0461`
Might take a couple of tries to pass CI. The UI test is x86-linux only; I'm not sure how to generalize it to other architectures.
r? ``@GuillaumeGomez``
Some `compare_method` tweaks
1. Make some of the comparison functions' names more regular
2. Reduce pub scope of some of the things in `compare_method`
~3. Remove some unnecessary opaque type handling code -- `InferCtxt` already is in a mode that doesn't define opaque types~
* moved to a different PR
4. Bubble up `ErrorGuaranteed` for region constraint errors in `compare_method` - Improves a redundant error message in one unit test.
5. Move the `compare_method` module to have a more general name, since it's more like `compare_impl_item` :)
6. Rename `collect_trait_impl_trait_tys`
Remove some totally duplicated files in `rustc_infer`
I have no idea why or how I duplicated these files from `compiler/rustc_infer/src/infer/error_reporting/note.rs`, but I did by accident, and nothing caught it 🤦
Implement allow-by-default `multiple_supertrait_upcastable` lint
The lint detects when an object-safe trait has multiple supertraits.
Enabled in libcore and liballoc as they are low-level enough that many embedded programs will use them.
r? `@nikomatsakis`
Account for `match` expr in single line
When encountering `match Some(42) { Some(x) => x, None => "" };`, output
```
error[E0308]: `match` arms have incompatible types
--> f53.rs:2:52
|
2 | let _ = match Some(42) { Some(x) => x, None => "" };
| -------------- - ^^ expected integer, found `&str`
| | |
| | this is found to be of type `{integer}`
| `match` arms have incompatible types
```
