Add annotations to the graphviz region graph on region origins

[amandasystems]

This adds

• (ex<'e>) for regions whose origin is existential, with name if one exists,
• (for<'p>) for regions whose origin is a placeholder, with name if one exists

For any region whose name we don't know, use '_.

This has helped my debugging and it doesn't create too bad clutter, I feel.

The change iswas ridiculously small, but I turned it into a separate PR so we can bikeshed the format.

The following snippet:

struct Co<'a>(&'a ());
struct Contra<'a>(fn(&'a ()));

// `exists<'e> forall<'p> 'p: 'e` -> ERROR
fn p_outlives_e(
    x: for<'e> fn(for<'p> fn(fn(fn(Contra<'e>, Co<'p>)))),
) -> fn(fn(fn(for<'unify> fn(Contra<'unify>, Co<'unify>)))) {
    x

Gives this graph:

[rustbot]

r? @matthewjasper

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[lcnr]

👍 on adding this to the graph in some form

maybe even

(for<'p>) (and for<'_>) [and (ex<'e>)], feel like it's not that much clutter (and I don#t have to lookup what p means :3 it's also helpful to know the name of existential hr regions 🤔 I guess we currently don't track the bound region for existential hr regions... I feel like we should :3

[lcnr]

I guess I don't know whether using for<T> for both universals in general and for instantiated universals (i.e. either assumed existential quantification or to prove universal quantification) is more confusing than not. It feels fairly natural for me, but I am a bad person to ask here :>

[amandasystems]

Nice, just the discussion I wanted to have!

[amandasystems]

👍 on adding this to the graph in some form

maybe even

(for<'p>) (and for<'_>) [and (ex<'e>)], feel like it's not that much clutter (and I don#t have to lookup what p means :3 it's also helpful to know the name of existential hr regions 🤔

Yeah, not having to look up what sigils means is... a good idea. I'll make that change!

[amandasystems]

...and now the names for existentials are in there too, if we have them!

[lcnr]

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit 648e3fc with merge ad601d7…

To cancel the try build, run the command @bors try cancel.

[rust-bors]

☀️ Try build successful (CI)
Build commit: ad601d7 (ad601d7b50bab72680f28b6b4d8830c0c0a5fece, parent: 61cb1e97fcf954c37d0a457a8084ed9ad8b3cb82)

[rust-timer]

Finished benchmarking commit (ad601d7): comparison URL.

Overall result: ❌ regressions - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.5%	[0.5%, 0.5%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary 3.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	3.9%	[3.9%, 3.9%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.9%	[3.9%, 3.9%]	1

Cycles

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

Binary size

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

Bootstrap: 464.27s -> 466.698s (0.52%)
Artifact size: 377.42 MiB -> 377.41 MiB (-0.00%)

[lcnr]

fun fact, entirely ignoring from_forall does not change anything, see #145091

@bors r+

[bors]

📌 Commit 648e3fc has been approved by lcnr

It is now in the queue for this repository.

[lcnr]

@bors rollup

the only perf change looks spurious to me

[jieyouxu]

Hi bors this already merged
@bors r-

[jieyouxu]

@rustbot label: -S-waiting-on-author +S-waiting-on-bors +merged-by-bors