Fix an ICE on an invalid `binding @ ...` in a tuple struct pattern #74557

jakubadamw · 2020-07-20T13:19:03Z

rust-highfive · 2020-07-20T13:19:06Z

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jakubadamw · 2020-07-20T13:24:59Z

@JohnTitor, oh, I see in #74539 (comment) that you have a better idea than this? 🙂

@jakubadamw Great! You should tweak src/librustc_ast_lowering/pat.rs not losing diags.

What do you mean by “not losing diags”? The thing is that AST lowering runs after name resolution. 🤔 How else could it “poison” that particular invalid binding? Sorry, I don't know the compiler very well, it's been years. 🙂

src/librustc_resolve/late.rs

nagisa · 2020-07-20T13:43:57Z

@bors r+

bors · 2020-07-20T13:43:59Z

📌 Commit db77a9e516ad37a730c19e3c008c7279b5767aa7 has been approved by nagisa

JohnTitor · 2020-07-20T13:46:29Z

src/test/ui/issues/issue-74539.rs

+    let e = E::A(2, 3);
+    match e {
+        E::A(x @ ..) => {  //~ ERROR `x @` is not allowed in a tuple
+            x //~ ERROR cannot find value `x` in this scope


Hmm, x should be found here?

@JohnTitor, this is a consequence of the nature of the fix. But I think you're right, this should be done differently.

jakubadamw · 2020-07-20T13:52:33Z

@JohnTitor, okay, I have now pushed a second commit with an alternate, simpler approach. But it leads to diagnostics that are, in my opinion, degraded compared to the status quo.

error: `x @` is not allowed in a tuple struct
  --> $DIR/issue-74539.rs:9:13
   |
LL |             x @ ..
   |             ^^^^^^ this is only allowed in slice patterns
   |
   = help: remove this and bind each tuple field independently
help: if you don't need to use the contents of x, discard the tuple's remaining fields
   |
LL |             ..
   |             ^^

error: `..` patterns are not allowed here
  --> $DIR/issue-74539.rs:9:17
   |
LL |             x @ ..
   |                 ^^
   |
   = note: only allowed in tuple, tuple struct, and slice patterns

error[E0023]: this pattern has 1 field, but the corresponding tuple variant has 2 fields
  --> $DIR/issue-74539.rs:8:9
   |
LL |       A(u8, u8),
   |       --------- tuple variant defined here
...
LL | /         E::A(
LL | |             x @ ..
LL | |         ) => { x }
   | |_________^ expected 2 fields, found 1

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0023`.

We end up with two extra diagnostics that do not contribute anything new.

Which solution seems better in your opinion?

JohnTitor · 2020-07-20T13:58:31Z

@jakubadamw Thanks for investigating more! I like the later diagnostics but let's hear opinion from @nagisa or someone from T-compiler.

nagisa · 2020-07-20T14:06:40Z

I personally like the former slightly more because its not as redundant (and x not being found is fine given that its a variable introduced by an error), but ultimately either error seems fine to me as either approach fixes the significantly more important problem – the ICE.

In the end the decision on diagnostics is something that @rust-lang/wg-diagnostics is responsible for and the diagnostics themselves can be iterated further in a separate PR that does not target a backport to beta or stable. If we want this to be backportable it needs to be as simple and obviously correct as it can possibly get.

jakubadamw · 2020-07-20T14:09:40Z

@nagisa, thank you. Looks like I stepped on your toes by pushing after your r+, sorry! 🙂 Yeah, I agree the first solution gives nicer results (although implementation wise it's not as simple as the second one). Should we await input from @rust-lang/wg-diagnostics or go ahead with the first approach? If the latter, then I can take back the redundant commits.

src/librustc_ast_lowering/pat.rs

jakubadamw · 2020-07-20T15:07:37Z

@nagisa, okay, I brought back the initial version. 🙂

nagisa · 2020-07-20T15:10:40Z

@bors r+

bors · 2020-07-20T15:10:41Z

📌 Commit 77a2fbb86e9a0cddc18722390d939e9bcd874c64 has been approved by nagisa

jakubadamw · 2020-07-20T17:36:26Z

@nagisa, pardon, this will need one more r+, as I had to tidy up the style per the failed build. 🙂

davidtwco · 2020-07-20T17:37:17Z

@bors r=nagisa

bors · 2020-07-20T17:37:18Z

📌 Commit f5e5eb6 has been approved by nagisa

estebank · 2020-07-20T18:38:00Z

src/librustc_resolve/late.rs

+                // In tuple struct patterns ignore the invalid `ident @ ...`.
+                // It will be handled as an error by the AST lowering.
+                PatKind::Ident(bmode, ident, ref sub)
+                    if !(is_tuple_struct_pat && sub.as_ref().filter(|p| p.is_rest()).is_some()) =>
+                {


This PR can be merged as is, but I think we could also add another branch that detects the case with PatKind::Ident(..) where .. is present and record it with a PartialRes::new(Res::Err), which should eliminate the second unnecessary error that complains about x not being defined. (Haven't looked at this deeply enough to be sure.)

@ghost

…arth Rollup of 13 pull requests Successful merges: - rust-lang#72714 (Fix debug assertion in typeck) - rust-lang#73197 (Impl Default for ranges) - rust-lang#73323 (wf: check foreign fn decls for well-formedness) - rust-lang#74051 (disallow non-static lifetimes in const generics) - rust-lang#74376 (test caching opt_const_param_of on disc) - rust-lang#74501 (Ayu theme: Use different background color for Run button) - rust-lang#74505 (Fix search input focus in ayu theme) - rust-lang#74522 (Update sanitizer docs) - rust-lang#74546 (Fix duplicate maybe_uninit_extra attribute) - rust-lang#74552 (Stabilize TAU constant.) - rust-lang#74555 (Improve "important traits" popup display on mobile) - rust-lang#74557 (Fix an ICE on an invalid `binding @ ...` in a tuple struct pattern) - rust-lang#74561 (update backtrace-rs) Failed merges: r? @ghost

pnkfelix · 2020-07-23T18:08:42Z

The beta nomination was discussed at weekly T-compiler meeting.

The stable nomination was also discussed at that same meeting.

At the end of both discussions, I noted (and @Mark-Simulacrum agreed) that we'd be more comfortable backporting this if it guarded against the scenario where this guard fires but the AST-lowering code, for whatever reason, doesn't signal an error.

In particular, we think that should be implementable via a delay_span_bug invocation.

Having said that, adding a delay_span_bug invocation is not a strict prerequisite for the backport; it is merely something we see as a "nice to have" since it would give us confidence that this change cannot cause a miscompilation down the road.

Having said that: beta backport approved, and stable backport approved.

@pnkfelix

delay_span_bug instead of silent ignore This is a follow-up to rust-lang#74557. r? @pnkfelix

@pnkfelix

delay_span_bug instead of silent ignore This is a follow-up to rust-lang#74557. r? @pnkfelix

Fix ICEs with `@ ..` binding This reverts rust-lang#74557 and introduces an alternative fix while ensuring that rust-lang#74954 is not broken. The diagnostics are verbose though, it fixes three related issues. cc rust-lang#74954, rust-lang#74539, and rust-lang#74702

cuviper · 2020-08-04T15:21:13Z

I've removed the beta backport labels. This was already backported to stable for 1.45.1, then reverted in 1.45.2 due to #74954. We'll let this release naturally with the follow-up fix in #74963.

rust-highfive assigned oli-obk Jul 20, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 20, 2020

nagisa reviewed Jul 20, 2020

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src/librustc_resolve/late.rs Outdated Show resolved Hide resolved

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 20, 2020

nagisa added stable-nominated Nominated for backporting to the compiler in the stable channel. beta-nominated Nominated for backporting to the compiler in the beta channel. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jul 20, 2020

JohnTitor reviewed Jul 20, 2020

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nagisa requested changes Jul 20, 2020

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src/librustc_ast_lowering/pat.rs Outdated Show resolved Hide resolved

Fix an ICE on an invalid binding @ ... in a tuple struct pattern

f5e5eb6

estebank reviewed Jul 20, 2020

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Manishearth mentioned this pull request Jul 20, 2020

Rollup of 13 pull requests #74569

Merged

bors merged commit 6bbf82d into rust-lang:master Jul 21, 2020

LeSeulArtichaut mentioned this pull request Jul 21, 2020

[stable] 1.45.1 release #74574

Merged

JohnTitor mentioned this pull request Jul 22, 2020

Improve diagnostics for an invalid binding in a tuple struct pattern #74641

Closed

pnkfelix added beta-accepted Accepted for backporting to the compiler in the beta channel. stable-accepted Accepted for backporting to the compiler in the stable channel. labels Jul 23, 2020

Mark-Simulacrum removed the stable-nominated Nominated for backporting to the compiler in the stable channel. label Jul 23, 2020

Mark-Simulacrum mentioned this pull request Jul 23, 2020

delay_span_bug instead of silent ignore #74692

Merged

petrochenkov mentioned this pull request Jul 24, 2020

ICE with the (foo @ ..,) pattern #74702

Closed

Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Jul 24, 2020

Rollup merge of rust-lang#74692 - Mark-Simulacrum:delay-bug, r=pnkfelix

7d545ed

delay_span_bug instead of silent ignore This is a follow-up to rust-lang#74557. r? @pnkfelix

Manishearth added a commit to Manishearth/rust that referenced this pull request Jul 24, 2020

Rollup merge of rust-lang#74692 - Mark-Simulacrum:delay-bug, r=pnkfelix

db83a21

delay_span_bug instead of silent ignore This is a follow-up to rust-lang#74557. r? @pnkfelix

cuviper mentioned this pull request Jul 30, 2020

Pattern matching regression 1.45.0 -> 1.45.1 (+nightly) #74954

Closed

JohnTitor mentioned this pull request Jul 30, 2020

Fix ICEs with @ .. binding #74963

Merged

cuviper removed beta-accepted Accepted for backporting to the compiler in the beta channel. beta-nominated Nominated for backporting to the compiler in the beta channel. labels Aug 4, 2020

JohnTitor mentioned this pull request Aug 4, 2020

ICE with the @ .. binding pattern #74539

Closed

cuviper added this to the 1.47.0 milestone May 2, 2024

Fix an ICE on an invalid binding @ ... in a tuple struct pattern #74557

Fix an ICE on an invalid binding @ ... in a tuple struct pattern #74557

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Fix an ICE on an invalid `binding @ ...` in a tuple struct pattern #74557

Fix an ICE on an invalid `binding @ ...` in a tuple struct pattern #74557

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