fix fn/const items implied bounds and wf check (rebase)

[lcnr]

A rebase of #104098, see that PR for discussion. This is pretty much entirely the work of @aliemjay. I received his permission for this rebase.

---

These are two distinct changes (edit: actually three, see below):

1. Wf-check all fn item args. This is a soundness fix.
   Fixes function type params are not checked for well-formedness #104005

2. Use implied bounds from impl header in borrowck of associated functions/consts. This strictly accepts more code and helps to mitigate the impact of other breaking changes.
   Fixes implied bounds from impl header are not used in associated functions/consts #98852
   Fixes Generic param requires bounds on call to function that is already required for calls to the caller #102611

The first is a breaking change and will likely have a big impact without the the second one. See the first commit for how it breaks libstd.

Landing the second one without the first will allow more incorrect code to pass. For example an exploit of #104005 would be as simple as:

use core::fmt::Display;

trait ExtendLt<Witness> {
    fn extend(self) -> Box<dyn Display>;
}

impl<T: Display> ExtendLt<&'static T> for T {
    fn extend(self) -> Box<dyn Display> {
        Box::new(self)
    }
}

fn main() {
    let val = (&String::new()).extend();
    println!("{val}");
}

The third change is to to check WF of user type annotations before normalizing them (fixes #104764, fixes #104763). It is mutually dependent on the second change above: an attempt to land it separately in #104746 caused several crater regressions that can all be mitigated by using the implied from the impl header. It is also necessary for the soundness of associated consts that use the implied bounds of impl header. See #104763 and how the third commit fixes the soundness issue in tests/ui/wf/wf-associated-const.rs that was introduces by the previous commit.

r? types

[lcnr]

@bors rollup=never

I've added a new known-bug test for #84591 in my rebase and removed tests/ui/wf/wf-in-fn-type-implicit.rs, given that this is the same test as tests/ui/borrowck/fn-item-check-type-params.rs.

All other changes were already reviewed by me in #104098. This change has been FCP'd in #104098 (comment) and will probably cause a minor perf regression #104098 (comment). This is expected as it does strictly more work

[BoxyUwU]

@bors r+ rollup=never

[bors]

📌 Commit 66090ef has been approved by BoxyUwU

It is now in the queue for this repository.

[bors]

⌛ Testing commit 66090ef with merge 6bf600b...

[bors]

☀️ Test successful - checks-actions
Approved by: BoxyUwU
Pushing 6bf600b to master...

[rust-timer]

Finished benchmarking commit (6bf600b): comparison URL.

Overall result: ❌ regressions - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.3%	[0.2%, 0.5%]	26
Regressions ❌ (secondary)	1.3%	[0.3%, 1.6%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[0.2%, 0.5%]	26

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
Regressions ❌ (secondary)	1.7%	[0.7%, 4.4%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.0%	[-6.0%, -6.0%]	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.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.2%	[2.2%, 2.2%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 663.655s -> 665.541s (0.28%)
Artifact size: 308.29 MiB -> 308.32 MiB (0.01%)

[Kobzol]

This was a fix that had an expected performance regression, marking as triaged.

@rustbot label: +perf-regression-triaged