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Improve diagnostics for functions in struct definitions #76808

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merged 3 commits into from
May 8, 2021

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LeSeulArtichaut
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Tries to implement #76421.
This is probably going to need unit tests, but I wanted to hear from review all the cases tests should cover.

I'd like to follow up with the "mechanically applicable suggestion here that adds an impl block" step, but I'd need guidance. My idea for now would be to try to parse a function, and if that succeeds, create a dummy ast::Item impl block to then format it using pprust. Would that be a viable approach? Is there a better alternative?

r? @matklad cc @estebank

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 16, 2020
@jyn514 jyn514 added A-diagnostics Area: Messages for errors, warnings, and lints T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 16, 2020
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jyn514 commented Sep 16, 2020

It would be helpful to add a UI test for the example in #76421 - even if it doesn't hit all the cases, it helps show that the diagnostic looks roughly right.

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LeSeulArtichaut commented Sep 17, 2020

@jyn514 I pushed the test

@crlf0710 crlf0710 added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 8, 2020
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@matklad any updates?

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r? @estebank

@rust-highfive rust-highfive assigned estebank and unassigned matklad Jan 31, 2021
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bors commented Mar 17, 2021

☔ The latest upstream changes (presumably #83188) made this pull request unmergeable. Please resolve the merge conflicts.

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@LeSeulArtichaut Do you want to just try to get the the current suggestion merged and then make a followup PR with an even better error? If so, then r=me on this, with or without an additional comment on the test.

In future PRs, I would like to see tests for unions or enums too. Or feel free to add that to this PR if it works.

compiler/rustc_parse/src/parser/item.rs Show resolved Hide resolved
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jackh726 commented May 3, 2021

r? @jackh726

@rust-highfive rust-highfive assigned jackh726 and unassigned estebank May 3, 2021
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jackh726 commented May 3, 2021

@bors delegate+

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bors commented May 3, 2021

✌️ @LeSeulArtichaut can now approve this pull request

@LeSeulArtichaut LeSeulArtichaut 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 May 5, 2021
@LeSeulArtichaut LeSeulArtichaut force-pushed the diagnose-functions-struct branch from 644975f to 6717f81 Compare May 7, 2021 20:50
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jackh726 commented May 7, 2021

@bors r+

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bors commented May 7, 2021

📌 Commit 6717f81 has been approved by jackh726

@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 May 7, 2021
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LeSeulArtichaut commented May 7, 2021

@jackh726 Enums did not work, I added a new commit to this PR. I also added a better test description as you requested.

Do you want to just try to get the the current suggestion merged and then make a followup PR with an even better error?

What would an "even better error" look like? Do you mean a machine-applicable suggestion that extracts the function to an impl block, as estebank suggested? If so I'd prefer that to be in a follow-up PR.

PS: you're too fast


let struct_def = if this.check(&token::OpenDelim(token::Brace)) {
// Parse a struct variant.
let (fields, recovered) = this.parse_record_struct_body()?;
let (fields, recovered) = this.parse_record_struct_body("struct")?;
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Note that this can give some slightly ankward results:

enum Foo {
    Variant {
        fn bar() {}
    }
}
error: functions are not allowed in struct definitions
 --> test.rs:5:9
  |
5 |         fn bar() {}
  |         ^^^^^^^^^^^
  |
  = help: unlike in C++, Java, and C#, functions are declared in `impl` blocks
  = help: see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information

Doesn't seem very important to me however

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Hmm, I see. If it comes up, a fairly easy fix might be to add a struct flag that is true in an actual struct and false in a enum variant.

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jackh726 commented May 7, 2021

What would an "even better error" look like? Do you mean a machine-applicable suggestion that extracts the function to an impl block, as estebank suggested? If so I'd prefer that to be in a follow-up PR.

Yeah, the machine-applicable suggestion.

PS: you're too fast

Only sometimes :)

bors added a commit to rust-lang-ci/rust that referenced this pull request May 8, 2021
Rollup of 6 pull requests

Successful merges:

 - rust-lang#76808 (Improve diagnostics for functions in `struct` definitions)
 - rust-lang#84887 (Remove SpanInterner::get)
 - rust-lang#85034 (fix null pointer error messages)
 - rust-lang#85038 (Don't stop running rustdoc-gui tests at first failure)
 - rust-lang#85044 (Use `path.exists()` instead of `fs::metadata(path).is_ok()`)
 - rust-lang#85052 (rustdoc: Link to the docs on namespaces when an unknown disambiguator is found)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit eb36bc6 into rust-lang:master May 8, 2021
@rustbot rustbot added this to the 1.54.0 milestone May 8, 2021
@LeSeulArtichaut LeSeulArtichaut deleted the diagnose-functions-struct branch May 8, 2021 10:54
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