EarlyBinder prevent misuse

[lcnr]

folding a type before substituting is pretty much always wrong and could happen by accident, e.g. see #99798 (comment)

this PR removes the TypeFoldable and TypeVisitable impl from EarlyBinder.

r? types cc @jackh726

[rustbot]

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[lcnr]

e.g. this was wrong in that it could result in unnormalized types, we should be able to write a testcase for this 🤷 but that seems like effort, so i am not going to do it

[lcnr]

and woops, wrong param env xd

[lcnr]

ok, it feels wrong but polymorphization breaks with this change, ah whatever.

[jackh726]

Any idea of a "proper" solution for polymorphism?

[lcnr]

well, two ideas:

1. don't normalize while computing whether we may polymorphize
2. only use the normalized types after polymorphization

thinking about this, it would be correct to normalize twice here: once to get to the state assumed by polymorphization, and then once after the subst call to actually have a fully normalized type.

Actually, the result of fn_sig_for_fn_abi is only used by fn_abi_new_uncached which does the following 😁

        let sig = self.tcx.normalize_erasing_late_bound_regions(self.param_env, sig);

so we don't have to normalize here at all, except to deal with 2. added a comment mentioning this.

[bors]

☔ The latest upstream changes (presumably #98588) made this pull request unmergeable. Please resolve the merge conflicts.

[compiler-errors]

I think this is fine to land now, since the polymorphism thing is already labeled with a // HACK comment.

r=me once rebased

[jackh726]

I would like at least some idea of what the plan to fix polymorphism might look like though.

(Though, I really do like the goal of this PR)

[lcnr]

@bors r=compiler-errors

[bors]

📌 Commit 0c3e01d has been approved by compiler-errors

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0c3e01d with merge 11bb80a...

[bors]

☀️ Test successful - checks-actions
Approved by: compiler-errors
Pushing 11bb80a to master...

[rust-highfive]

📣 Toolstate changed by #101901!

Tested on commit 11bb80a.
Direct link to PR: #101901

💔 miri on windows: test-fail → build-fail (cc @oli-obk @RalfJung).
💔 miri on linux: test-fail → build-fail (cc @oli-obk @RalfJung).

[rust-timer]

Finished benchmarking commit (11bb80a): 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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.1%	[-4.1%, -4.1%]	1
All ❌✅ (primary)	-	-	0

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.

	mean1	range	count2
Regressions ❌ (primary)	2.1%	[2.1%, 2.1%]	1
Regressions ❌ (secondary)	2.0%	[2.0%, 2.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.1%	[-2.1%, -2.1%]	1
All ❌✅ (primary)	2.1%	[2.1%, 2.1%]	1

Footnotes

1. the arithmetic mean of the percent change ↩ ↩²

2. number of relevant changes ↩ ↩²