Double check that hidden types match the expected hidden type #113661

oli-obk · 2023-07-13T16:26:29Z

Fixes #113278 specifically, but I left a TODO for where we should also add some hardening.

It feels a bit like papering over the issue, but at least this way we don't get unsoundness, but just surprising errors. Errors will be improved and given spans before this PR lands.

r? @compiler-errors @lcnr

rustbot · 2023-07-13T16:26:38Z

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rustbot · 2023-07-13T16:26:42Z

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

compiler/rustc_hir_analysis/src/check/check.rs

lcnr · 2023-07-17T09:10:11Z

compiler/rustc_const_eval/src/util/compare_types.rs

+            "{}, {}",
+            tcx.type_of(key.def_id).subst(tcx, key.substs),
+            ty.hidden_type.ty
+        );


I feel like we should hit this bug? 🤔 or do we avoid it because we have OpaqueCast everywhere we would assign to/from opaques?

I was surprised, too, but I didn't debug it.

do we run the validator before optimizations by default 😅 iirc we only do it with -Zvalidate-mir 🤔

compiler/rustc_hir_analysis/src/check/check.rs

tests/ui/type-alias-impl-trait/nested-rpit-with-lifetimes.rs

compiler/rustc_hir_analysis/src/check/check.rs

lcnr · 2023-07-24T15:01:58Z

compiler/rustc_hir_analysis/src/check/check.rs

+/// // desugared to
+///
+/// // hidden type is `&'bDup ()`
+/// // During wfcheck the hidden type of `Inner` is `&'a ()`, but


Suggested change

/// // During wfcheck the hidden type of `Inner` is `&'a ()`, but

/// // During wfcheck the hidden type of `Inner` is `&'b ()`, but

i feel like it is a bit weird to talk about 'bDup if it is unclear where 'b comes from. I prefer using 'a and 'aDup everywhere

well... unless I double confused myself, your diff is wrong, so it's good that I made it explicit 😆

how can the inner type in wf check be 'a if we wf check in the scope of the opaque type which does not have a 'a in scope? 😅

also, "During wfcheck of Outer ...", would make this clearer I think

because RPITs aren't desugerable currently (ok I guess that's what you meant by "unclear where 'b comes from"), they only work by construction and are cheating. I rewrote the example to be more like how it actually works, is that clearer?

lcnr

r=me after final comment nits

lcnr

accurately documenting the desugaring is messy (because the desugaring is messy :3)

because RPITs aren't desugerable currently (ok I guess that's what you meant by "unclear where 'b comes from"), they only work by construction and are cheating. I rewrote the example to be more like how it actually works, is that clearer?

idk 😅 i don't know how much of my nits are "the actual impl is a mess" and how much is "the comment is wrong/incomplete"

lcnr · 2023-07-25T07:55:35Z

compiler/rustc_hir_analysis/src/check/check.rs

@@ -545,17 +545,23 @@ fn sanity_check_found_hidden_type<'tcx>(
 /// }
 /// fn func<'a>(x: &'a ()) -> impl Id<Assoc = impl Sized + 'a> { x }
 /// // desugared to
+/// fn func<'a>(x: &'a () -> Outer<'a, Assoc = Inner<'a>> {


Suggested change

/// fn func<'a>(x: &'a () -> Outer<'a, Assoc = Inner<'a>> {

/// fn func<'a>(x: &'a () -> Outer<'a, 'a> {

? 🤔

yea... I don't know how to represent the fact that we walk the item bounds of Outer

lcnr · 2023-07-25T07:55:59Z

compiler/rustc_hir_analysis/src/check/check.rs

-/// // hidden type is `&'cDup ()`
-/// type Inner<'c, 'cDup> = impl Sized + 'cDup;
-/// fn func<'a>(x: &'a () -> Outer<'static, 'a> { x }
+///     // hidden type is `&'aDupOuter ()`


This feels wrong, if the hidden type of Outer is &'aDupOuter (), shouldn't wf check of Outer define the hidden type of Inner to be <&'aDupOuter () as Id>::Assoc which is &'aDupOuter (), so this should worK?

No, because we figure out the hidden type of Inner anew during wf check of Outer, we don't get it from type_of. We get the hidden type of Outer, which is &'a (), so the id projection is also &'a ()

lcnr · 2023-07-25T07:56:21Z

compiler/rustc_hir_analysis/src/check/check.rs

+///     // So we walk the signature of `func` to find the use of `Inner<'a>`
+///     // and then use that to replace the lifetimes in the hidden type, obtaining
+///     // `&'a ()`.
+///     type Outer<'aDupOuter> = impl Id<Assoc = Inner<'aDupOuter>>;


is the 'a param of Inner 'a or 'aDupOuter here?

'a, it is inherited from the function.

oli-obk · 2023-07-25T13:43:38Z

@bors r=lcnr

bors · 2023-07-25T13:43:40Z

📌 Commit df4bfd9 has been approved by lcnr

It is now in the queue for this repository.

bors · 2023-07-25T16:18:28Z

⌛ Testing commit df4bfd9 with merge 50bb51b2201e3aa6ca651a9446f62088ca32d9f0...

bors · 2023-07-25T16:53:00Z

💔 Test failed - checks-actions

rust-log-analyzer · 2023-07-25T16:54:02Z

A job failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

oli-obk · 2023-07-25T17:04:31Z

@bors retry nothing failed? Not sure what happened

…iaskrgr Rollup of 5 pull requests Successful merges: - rust-lang#112995 (Check for `<&NotClone as Clone>::clone()` calls and suggest to add Clone trait appropriately) - rust-lang#113578 (Don't say that a type is uncallable if its fn signature has errors in it) - rust-lang#113661 (Double check that hidden types match the expected hidden type) - rust-lang#114044 (factor out more stable impls) - rust-lang#114062 (CI: split nested GHA groups instead of panicking) r? `@ghost` `@rustbot` modify labels: rollup

… r=jackh726 Paper over an accidental regression r? types cc rust-lang#115781 (do not close issue until beta backport has been performed) The PR reasons are explained with comments in the source. In order to keep the diff simple, this PR effectively reverts rust-lang#113661, but only for RPITs. I will submit a follow up PR that fixes this correctly instead of just disabling the newly added check for RPITs. This PR should be significantly easier to review for beta backport

Rollup merge of rust-lang#115844 - oli-obk:opaque_lifetime_ambiguity, r=jackh726 Paper over an accidental regression r? types cc rust-lang#115781 (do not close issue until beta backport has been performed) The PR reasons are explained with comments in the source. In order to keep the diff simple, this PR effectively reverts rust-lang#113661, but only for RPITs. I will submit a follow up PR that fixes this correctly instead of just disabling the newly added check for RPITs. This PR should be significantly easier to review for beta backport

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oli-obk commented Jul 14, 2023

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Double check that hidden types match the expected hidden type

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Explain what the heck is going on with this lifetime remapping business

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Some documentation nits

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Explain RPITs in the way they actually work

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Try explaining where Inner is in the signature better

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matthiaskrgr mentioned this pull request Jul 25, 2023

Rollup of 5 pull requests #114076

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bors merged commit 0b13deb into rust-lang:master Jul 26, 2023

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matthiaskrgr mentioned this pull request Jul 27, 2023

ICE: compiler/rustc_const_eval/src/util/compare_types.rs #114121

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oli-obk deleted the tait_wtf branch July 27, 2023 08:13

lqd mentioned this pull request Jul 31, 2023

ICE: Region parameter out of range when substituting in region #114285

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oli-obk mentioned this pull request Aug 7, 2023

Stop using identity args for RPIT wf checks #114574

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Nashenas88 mentioned this pull request Aug 7, 2023

Two conflicting concrete types for the same opaque type #114597

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apiraino mentioned this pull request Sep 14, 2023

regression: concrete type differs from previous defining opaque type use #115781

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oli-obk mentioned this pull request Sep 14, 2023

Paper over an accidental regression #115844

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aliemjay mentioned this pull request Mar 24, 2024

TAITs with different args incorrectly assumed to be equal #122876

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Double check that hidden types match the expected hidden type #113661

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	/// // During wfcheck the hidden type of `Inner` is `&'a ()`, but
	/// // During wfcheck the hidden type of `Inner` is `&'b ()`, but

	/// fn func<'a>(x: &'a () -> Outer<'a, Assoc = Inner<'a>> {
	/// fn func<'a>(x: &'a () -> Outer<'a, 'a> {

Double check that hidden types match the expected hidden type #113661

Double check that hidden types match the expected hidden type #113661

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