Show more information when multiple impls apply

[estebank]

• When there are impls without type params, show only those (to avoid showing overly generic impls).

error[E0283]: type annotations needed
  --> $DIR/multiple-impl-apply.rs:34:9
   |
LL |     let y = x.into();
   |         ^     ---- type must be known at this point
   |
note: multiple `impl`s satisfying `_: From<Baz>` found
  --> $DIR/multiple-impl-apply.rs:14:1
   |
LL | impl From<Baz> for Bar {
   | ^^^^^^^^^^^^^^^^^^^^^^
...
LL | impl From<Baz> for Foo {
   | ^^^^^^^^^^^^^^^^^^^^^^
   = note: required for `Baz` to implement `Into<_>`
help: consider giving `y` an explicit type
   |
LL |     let y: /* Type */ = x.into();
   |          ++++++++++++

• Lower the importance of T: Sized, T: WellFormed and coercion errors, to prioritize more relevant errors. The pre-existing deduplication logic deals with hiding redundant errors better that way, and we show errors with more metadata that is useful to the user.

• Show <SelfTy as Trait>::assoc_fn suggestion in more cases.

error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
  --> $DIR/cross-return-site-inference.rs:38:16
   |
LL |     return Err(From::from("foo"));
   |                ^^^^^^^^^^ cannot call associated function of trait
   |
help: use a fully-qualified path to a specific available implementation
   |
LL |     return Err(</* self type */ as From>::from("foo"));
   |                +++++++++++++++++++     +

Fix #88284.

[rustbot]

r? @wesleywiser

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Some changes occurred in engine.rs, potentially modifying the public API of ObligationCtxt.

cc @lcnr, @compiler-errors

Some changes occurred in need_type_info.rs

cc @lcnr

Can you fix up the history of this PR as well? Some of the intermediate changes like formatting and rebase fallout can probably be squashed down into the PRs that they're most closely related to.

Can you find a better representative for E0282? This is trivially ambiguous, but I think this error should have a more descriptive example.

Also, the description below doesn't match this example.

☔ The latest upstream changes (presumably #115897) made this pull request unmergeable. Please resolve the merge conflicts.

Needs rebase

tidy error: /checkout/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs: too many lines (3023) (add // ignore-tidy-filelength to the file to suppress this error)

r=me when CI is green 🙂

Split the file instead.

@bors r=wesleywiser

📌 Commit b3eec8b has been approved by wesleywiser

It is now in the queue for this repository.

⌛ Testing commit b3eec8b with merge 883fa79...

This better work or I'm gonna pull what remains of my hair out.

@bors r=wesleywiser

📌 Commit 4483ac2 has been approved by wesleywiser

It is now in the queue for this repository.

⌛ Testing commit 4483ac2 with merge 94bc9c7...

☀️ Test successful - checks-actions
Approved by: wesleywiser
Pushing 94bc9c7 to master...

Thank you @estebank!

Finished benchmarking commit (94bc9c7): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	3.2%	[3.2%, 3.2%]	1
Regressions ❌ (secondary)	4.3%	[4.3%, 4.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.3%	[-1.3%, -1.3%]	1
All ❌✅ (primary)	3.2%	[3.2%, 3.2%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 623.951s -> 623.472s (-0.08%)
Artifact size: 270.64 MiB -> 270.63 MiB (-0.00%)