Register normalization obligations instead of immediately normalizing in opaque type instantiation

[oli-obk]

For lazy TAIT we will need to instantiate opaque types from within rustc_infer, which cannot invoke normalization methods (they are in rustc_trait_resolution). So before we move the logic over to rustc_infer, we need make sure no normalization happens anymore. This PR resolves that by just registering normalization obligations and continuing.

This PR is best reviewed commit by commit

I also included f7ad36e which is just an independent cleanup that touches the same code and reduces diagnostics noise a bit

r? @nikomatsakis cc @spastorino

[nikomatsakis]

Comment please =) What is the purpose of this function?

[nikomatsakis]

r=me once comment is added

[oli-obk]

@bors r=nikomatsakis

[bors]

📌 Commit fc75914ae52f86e856bb32079caf75dde704bda7 has been approved by nikomatsakis

[bors]

☔ The latest upstream changes (presumably #88980) made this pull request unmergeable. Please resolve the merge conflicts.

[oli-obk]

@bors try @rust-timer queue

[bors]

🙅 Please do not try after a pull request has been r+ed. If you need to try, unapprove (r-) it first.

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[oli-obk]

@bors r-

[oli-obk]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

🔒 Merge conflict

This pull request and the master branch diverged in a way that cannot be automatically merged. Please rebase on top of the latest master branch, and let the reviewer approve again.

How do I rebase?

Assuming self is your fork and upstream is this repository, you can resolve the conflict following these steps:

1. git checkout lazy_normalization_in_opaque_types (switch to your branch)
2. git fetch upstream master (retrieve the latest master)
3. git rebase upstream/master -p (rebase on top of it)
4. Follow the on-screen instruction to resolve conflicts (check git status if you got lost).
5. git push self lazy_normalization_in_opaque_types --force-with-lease (update this PR)

You may also read Git Rebasing to Resolve Conflicts by Drew Blessing for a short tutorial.

Please avoid the "Resolve conflicts" button on GitHub. It uses git merge instead of git rebase which makes the PR commit history more difficult to read.

Sometimes step 4 will complete without asking for resolution. This is usually due to difference between how Cargo.lock conflict is handled during merge and rebase. This is normal, and you should still perform step 5 to update this PR.

Error message

Auto-merging compiler/rustc_trait_selection/src/opaque_types.rs
CONFLICT (content): Merge conflict in compiler/rustc_trait_selection/src/opaque_types.rs
Automatic merge failed; fix conflicts and then commit the result.

[oli-obk]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit afb7472 with merge e5e1870d75756ab1996687c3b9ebe7af4122c036...

[bors]

☀️ Try build successful - checks-actions
Build commit: e5e1870d75756ab1996687c3b9ebe7af4122c036 (e5e1870d75756ab1996687c3b9ebe7af4122c036)

[rust-timer]

Queued e5e1870d75756ab1996687c3b9ebe7af4122c036 with parent db1fb85, future comparison URL.

[rust-timer]

Finished benchmarking commit (e5e1870d75756ab1996687c3b9ebe7af4122c036): comparison url.

Summary: This change led to small relevant mixed results 🤷 in compiler performance.

• Small improvement in instruction counts (up to -0.5% on full builds of coercions)
• Small regression in instruction counts (up to 0.4% on incr-full builds of ctfe-stress-4)

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

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 led 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-review -S-waiting-on-perf +perf-regression

[oli-obk]

looks like codegen noise to me, and this PR should not affect codegen at all, it's purely in the type system

@rustbot label: +perf-regression-triaged

@bors r=nikomatsakis

[bors]

📌 Commit afb7472 has been approved by nikomatsakis

[bors]

⌛ Testing commit afb7472 with merge dda2a0e...

[bors]

☀️ Test successful - checks-actions
Approved by: nikomatsakis
Pushing dda2a0e to master...

[rust-timer]

Finished benchmarking commit (dda2a0e): comparison url.

Summary: This benchmark run did not return any relevant changes.

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression