Fast path for stalled obligations on self ty

[compiler-errors]

If we see that the self type of a goal is an infer var, then don't try to compute the goal at all, since we know that it'll be forced ambiguous.

This is currently only implemented when there are no opaques in the environment. We could extend it to check that the self type is not related to any already defined opaques via subtyping, but I'll leave that as a follow-up.

---

Also stall coerce and subtype predicates if both of their vars are not resolved to concrete types.

---

Also, we don't care if the goal is higher-ranked for the sized and copy/clone fast path. pulling this out into another PR.

r? lcnr

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit fb285af with merge fa369e6...

[bors]

☀️ Try build successful - checks-actions
Build commit: fa369e6 (fa369e6ddc2f81c31d5ded57f79518262940b5d6)

[rust-timer]

Finished benchmarking commit (fa369e6): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.5%	[0.5%, 0.5%]	1
Improvements ✅ (primary)	-0.2%	[-0.3%, -0.1%]	6
Improvements ✅ (secondary)	-7.8%	[-29.0%, -0.1%]	15
All ❌✅ (primary)	-0.2%	[-0.3%, -0.1%]	6

Max RSS (memory usage)

Results (primary -1.0%, secondary -3.8%)

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
Regressions ❌ (secondary)	1.8%	[1.3%, 2.3%]	2
Improvements ✅ (primary)	-1.0%	[-1.0%, -1.0%]	1
Improvements ✅ (secondary)	-5.7%	[-8.7%, -4.7%]	6
All ❌✅ (primary)	-1.0%	[-1.0%, -1.0%]	1

Cycles

Results (secondary -12.3%)

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-12.3%	[-25.0%, -2.1%]	7
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 778.889s -> 779.678s (0.10%)
Artifact size: 368.42 MiB -> 366.35 MiB (-0.56%)

[rustbot]

Some changes occurred to the core trait solver

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

[bors]

☔ The latest upstream changes (presumably #141731) made this pull request unmergeable. Please resolve the merge conflicts.

[compiler-errors]

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit 9899464 with merge 039888f…

[rust-bors]

☀️ Try build successful (CI)
Build commit: 039888f (039888fc2fe51ca95ed23c75d554793192d536e0)

[rust-timer]

Finished benchmarking commit (039888f): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	3
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	3
Improvements ✅ (secondary)	-9.0%	[-50.3%, -0.2%]	20
All ❌✅ (primary)	-0.2%	[-0.2%, -0.2%]	3

Max RSS (memory usage)

Results (secondary 0.7%)

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
Regressions ❌ (secondary)	0.9%	[0.4%, 1.6%]	13
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.4%	[-0.5%, -0.4%]	3
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -7.9%)

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
Regressions ❌ (secondary)	1.2%	[0.7%, 1.7%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-9.1%	[-43.1%, -0.4%]	16
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 743.192s -> 742.766s (-0.06%)
Artifact size: 372.27 MiB -> 372.37 MiB (0.03%)

[lcnr]

@bors r+

[bors]

📌 Commit 9899464 has been approved by lcnr

It is now in the queue for this repository.