Fix depth check in ProofTreeVisitor.

[gavinleroy]

The hack to cutoff overflows and cycles in the new trait solver was incorrect. We want to inspect everything with depth [0..10].

This fix exposed a previously unseen bug, which caused the compiler to ICE when invoking trait_ref on a non-assoc type projection. I simply added the guard in the AmbiguityCausesVisitor, and updated the expected output for the auto-trait-coherence test which now includes the extra note:

   |
   = note: upstream crates may add a new impl of trait `std::marker::Send` for type `OpaqueType` in future versions

r? @lcnr

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @lcnr (or someone else) soon.

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[rustbot]

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

[rustbot]

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

[lcnr]

thanks 👍

@bors r+ rollup

[bors]

📌 Commit caae1e0 has been approved by lcnr

It is now in the queue for this repository.

[bors]

⌛ Testing commit caae1e0 with merge 6b771f6...

[bors]

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 6b771f6 to master...

[rust-timer]

Finished benchmarking commit (6b771f6): 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)	0.7%	[0.5%, 1.0%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.5%	[-1.5%, -1.5%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.0%	[-1.5%, 1.0%]	3

Cycles

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)	0.5%	[0.5%, 0.5%]	3
Regressions ❌ (secondary)	1.2%	[1.2%, 1.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[0.5%, 0.5%]	3

Binary size

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

Bootstrap: 675.256s -> 674.719s (-0.08%)
Artifact size: 311.08 MiB -> 311.08 MiB (0.00%)