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Improve handling of expr->field errors #124200

Merged
merged 1 commit into from
Apr 23, 2024
Merged

Improve handling of expr->field errors #124200

merged 1 commit into from
Apr 23, 2024

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scrabsha
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@scrabsha scrabsha commented Apr 20, 2024 •
edited by fmease
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The current message for "-> used for field access" is the following:

error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `->`
 --> src/main.rs:2:6
  |
2 |     a->b;
  |      ^^ expected one of 8 possible tokens

(playground link)

This PR tries to address this by adding a dedicated error message and recovery. The proposed error message is:

error: `->` used for field access or method call
 --> ./tiny_test.rs:2:6
  |
2 |     a->b;
  |      ^^ help: try using `.` instead
  |
  = help: the `.` operator will dereference the value if needed

(feel free to bikeshed it as much as necessary)

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rustbot commented Apr 20, 2024

r? @wesleywiser

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Apr 20, 2024
compiler-errors
compiler-errors reviewed Apr 20, 2024
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compiler/rustc_parse/src/parser/expr.rs Outdated
Comment on lines 987 to 989
// We make sure the `expr` and `->` are adjacent because we don't want to trigger the
// recovery for function signature.
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Why would this happen?

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Removing this makes issue-118530-ice.rs fail. I tried hard to understand this test. My understanding is that line 5 is a function signature, but I'd love to be corrected.

While avoiding this failure by checking the spans is not ideal, this indeed works and is consistent with how people space their -> in function prototypes and don't space their -> when accessing fields.

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i feel pretty strongly that we shouldn't be using token connectedness to do this recovery -- if that test ICEs, it would be useful to understand why that happens and fix the recovery rather than just paper it over.

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@compiler-errors compiler-errors Apr 20, 2024 •
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Also, i feel like removing the spaces around the -> in that test example should cause it to still ICE?

if so, this PR still introduces new bugs, and those should be fixed.

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also pls squash this into one commit

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also pls squash this into one commit

@compiler-errors ah, sorry. I thought making multiple was helpful for the review. This won't happen again.

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It's literally nbd!

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fmease commented Apr 20, 2024

If I'm not mistaken, this PR regresses the following artificial code snippet:

Wait, no it shouldn't 🤦

@fmease fmease assigned compiler-errors and fmease and unassigned wesleywiser Apr 20, 2024
@compiler-errors compiler-errors removed their assignment Apr 21, 2024
@fmease fmease added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 21, 2024
@scrabsha
Improve handling of expr->field errors
98332c1 
The current message for "`->` used for field access" is the following:

```rust
error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `->`
 --> src/main.rs:2:6
  |
2 |     a->b;
  |      ^^ expected one of 8 possible tokens
```

(playground link[1])

This PR tries to address this by adding a dedicated error message and recovery. The proposed error message is:

```
error: `->` used for field access or method call
 --> ./tiny_test.rs:2:6
  |
2 |     a->b;
  |      ^^ help: try using `.` instead
  |
  = help: the `.` operator will dereference the value if needed
```

(feel free to bikeshed it as much as necessary)

[1]: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=7f8b6f4433aa7866124123575456f54e

Signed-off-by: Sasha Pourcelot <[email protected]>
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@rustbot label -S-waiting-on-author +S-waiting-on-review

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 22, 2024
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👍 thanks for dealing w/ the back and forth

@bors r=compiler-errors,fmease

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bors commented Apr 22, 2024

📌 Commit 98332c1 has been approved by compiler-errors,fmease

It is now in the queue for this repository.

@bors 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 Apr 22, 2024
@matthiaskrgr matthiaskrgr mentioned this pull request Apr 23, 2024
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Apr 23, 2024
@bors
Auto merge of rust-lang#124277 - matthiaskrgr:rollup-zdb93i4, r=matth…
c672773 
…iaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#123680 (Deny gen keyword in `edition_2024_compat` lints)
 - rust-lang#124057 (Fix ICE when ADT tail has type error)
 - rust-lang#124168 (Use `DefiningOpaqueTypes::Yes` in rustdoc, where the `InferCtxt` is guaranteed to have no opaque types it can define)
 - rust-lang#124197 (Move duplicated code in functions in `tests/rustdoc-gui/notable-trait.goml`)
 - rust-lang#124200 (Improve handling of expr->field errors)
 - rust-lang#124220 (Miri: detect wrong vtables in wide pointers)
 - rust-lang#124266 (remove an unused type from the reentrant lock tests)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 5800e2a into rust-lang:master Apr 23, 2024
12 checks passed
@rustbot rustbot added this to the 1.79.0 milestone Apr 23, 2024
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Apr 23, 2024
@rust-timer
Unrolled build for rust-lang#124200
fc10cb0 
Rollup merge of rust-lang#124200 - scrabsha:sasha/->, r=compiler-errors,fmease

Improve handling of expr->field errors

The current message for "`->` used for field access" is the following:

```rust
error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, `}`, or an operator, found `->`
 --> src/main.rs:2:6
  |
2 |     a->b;
  |      ^^ expected one of 8 possible tokens
```

([playground link](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=7f8b6f4433aa7866124123575456f54e))

This PR tries to address this by adding a dedicated error message and recovery. The proposed error message is:

```
error: `->` used for field access or method call
 --> ./tiny_test.rs:2:6
  |
2 |     a->b;
  |      ^^ help: try using `.` instead
  |
  = help: the `.` operator will dereference the value if needed
```

(feel free to bikeshed it as much as necessary)
@scrabsha scrabsha deleted the sasha/-> branch April 23, 2024 10:54
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