Pretty print Fn traits in rustc_on_unimplemented

[compiler-errors]

I don't think that users really ever should need to think about Fn* traits' tupled args for a simple trait error.

r? diagnostics

[davidtwco]

Apologies for the delay in getting to this, LGTM.

[davidtwco]

r=me after rebasing

[compiler-errors]

@bors r=davidtwco

[bors]

📌 Commit c83f642 has been approved by davidtwco

It is now in the queue for this repository.

[bors]

⌛ Testing commit c83f642 with merge 1d6f05f...

[bors]

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing 1d6f05f to master...

[rust-timer]

Finished benchmarking commit (1d6f05f): 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)	2.7%	[0.8%, 3.6%]	4
Regressions ❌ (secondary)	3.3%	[2.0%, 4.6%]	2
Improvements ✅ (primary)	-1.6%	[-1.6%, -1.6%]	1
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	1.8%	[-1.6%, 3.6%]	5

Cycles

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

Binary size

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)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	3
All ❌✅ (primary)	-	-	0

Bootstrap: 636.121s -> 637.374s (0.20%)
Artifact size: 304.58 MiB -> 304.45 MiB (-0.04%)