Suggest using an appropriate keyword for `struct` and `enum` #94996

TaKO8Ki · 2022-03-16T09:36:50Z

rust-highfive · 2022-03-16T09:36:53Z

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nagisa · 2022-03-20T15:02:48Z

src/test/ui/proc-macro/derive-bad.stderr

+help: consider using `enum` instead of `struct`
+   |
+LL | #[derive(enum)]
+   |          ~~~~


Seems like this shouldn't happen, the suggested replacement has 0 chance to work at all.

I fixed it.

nagisa · 2022-03-20T15:10:19Z

src/test/ui/suggestions/suggest-using-appropriate-keyword-for-struct-and-enum.stderr

+help: consider using `enum` instead of `struct`
+   |
+LL | pub enum NotStruct {
+   |     ~~~~


I'm not entirely sure if we should be as trigger happy as proposed here about suggesting a different ADT type. I feel like it is much more likely that an ADT body will contain mistakes compared to user having specified a wrong kind of ADT.

Here it feels like the user was much more likely to just have forgetten to specify a type : _ for whatever reason. Though I could still see us making a suggestion as proposed here if there was at least one variant with data. That is in cases like these:

pub struct NotStruct { Variant, Variant2(u8), }

I agree with nagisa's comment. I think that for a case as ambiguous as these we might be better served by pointing at all the relevant places and let the user figure what they wanted. That could be done for cases like this one by adding a label to the struct keyword saying "while parsing this struct".

The comment above is still valid. I would prefer to simplify the logic and "just" add a span_label pointing at the item type being parsed. The likelihood of false positives is too high as it is.

nagisa · 2022-03-20T15:12:27Z

compiler/rustc_parse/src/parser/item.rs

@@ -1176,13 +1178,14 @@ impl<'a> Parser<'a> {
    }

    /// Parses an enum declaration.
-    fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
+    fn parse_item_enum(&mut self, start_span: Span) -> PResult<'a, ItemInfo> {


start_span seems a little misnomer here, given that the span begins at the enum or struct keyword, rather than covering the entire item (i.e. including the qualifiers such as pub). Maybe something like keyword_span would work better?

nagisa · 2022-03-20T15:18:45Z

compiler/rustc_parse/src/parser/item.rs

+                        Ok(_) => {
+                            let mut err = this.struct_span_err(
+                                enum_field_start_span.to(this.prev_token.span),
+                                "the enum cannot have a struct field declaration",


Diagnostics in parser largely follow a “expected ...” style of messages. The suggested wording would likely be more consistent with the rest of the diagnostics coming from the parser.

Suggested change

"the enum cannot have a struct field declaration",

"expected an `enum` variant, found a field",

nagisa · 2022-03-20T15:23:22Z

compiler/rustc_parse/src/parser/item.rs

+            let (fields, recovered) = self.parse_record_struct_body(
+                "union",
+                generics.where_clause.has_where_token,
+                None,


If we're handling structs, we should also handle unions.

nagisa · 2022-03-20T15:29:49Z

compiler/rustc_parse/src/parser/item.rs

+                            );
+                            err.span_suggestion_verbose(
+                                start_span,
+                                "consider using `struct` instead of `enum`",


Hm, an union could also make sense here, wouldn't it? While it is comparatively much rarer, looking to define an enum like this may very well be thinking of an union in the first place.

Suggested change

"consider using `struct` instead of `enum`",

"consider defining a `struct` or an `union` instead of an `enum`",

Not entirely sure how or if span_suggestion can provide multiple alternative replacements, though.

It might very well be that this suggestion is largely superfluous with the improved error message.

nagisa · 2022-03-20T15:31:56Z

I'm going to pass this on to @estebank for a further review, since they have a better grasp over the overall direction of diagnostics in Rust.

nagisa · 2022-03-20T15:32:03Z

r? @estebank

estebank · 2022-03-22T01:32:36Z

Let's make sure we have tests to avoid regressing on knock down errors (let's have a struct and enum with multiple variants and fields to see that we only emit a single error for them).

TaKO8Ki · 2022-03-22T03:16:01Z

@estebank
Ok! I am going to improve it.

apiraino · 2022-04-07T10:11:29Z

Switching review labels until PR is ready again for review, thanks!

@rustbot author

bors · 2022-04-28T22:23:08Z

☔ The latest upstream changes (presumably #96528) made this pull request unmergeable. Please resolve the merge conflicts.

…nion-ident, r=estebank Add a label to struct/enum/union ident name Based on rust-lang#94996 (comment) cc: ``@estebank``

…on-ident, r=estebank Add a label to struct/enum/union ident name Based on rust-lang#94996 (comment) cc: `@estebank`

rust-highfive assigned nagisa Mar 16, 2022

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Mar 16, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 16, 2022

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TaKO8Ki changed the title ~~Suggest using a appropriate keyword for struct and enum~~ Suggest using an appropriate keyword for struct and enum Mar 16, 2022

nagisa reviewed Mar 20, 2022

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rust-highfive assigned estebank and unassigned nagisa Mar 20, 2022

rustbot 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 7, 2022

TaKO8Ki added 3 commits April 10, 2022 11:47

suggest using a appropriate keyword for struct and enum

eff6598

fix derive-bad.stderr

f50da2e

not suggest if span originates in a derive-macro's expansion

f49601d

TaKO8Ki force-pushed the suggest-using-appropriate-keyword-for-struct-and-enum branch from c0d2c11 to f49601d Compare April 10, 2022 02:48

Dylan-DPC 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 Jul 18, 2022

TaKO8Ki mentioned this pull request Sep 26, 2022

Add a label to struct/enum/union ident name #102314

Merged

notriddle added a commit to notriddle/rust that referenced this pull request Sep 26, 2022

Rollup merge of rust-lang#102314 - TaKO8Ki:add-label-to-struct-enum-u…

c455dac

…nion-ident, r=estebank Add a label to struct/enum/union ident name Based on rust-lang#94996 (comment) cc: ``@estebank``

bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 27, 2022

Auto merge of rust-lang#102314 - TaKO8Ki:add-label-to-struct-enum-uni…

d9297d2

…on-ident, r=estebank Add a label to struct/enum/union ident name Based on rust-lang#94996 (comment) cc: `@estebank`

TaKO8Ki closed this Sep 27, 2022

TaKO8Ki deleted the suggest-using-appropriate-keyword-for-struct-and-enum branch September 27, 2022 10:47

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Suggest using an appropriate keyword for `struct` and `enum` #94996

Suggest using an appropriate keyword for `struct` and `enum` #94996

TaKO8Ki commented Mar 16, 2022

rust-highfive commented Mar 16, 2022

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nagisa Mar 20, 2022

TaKO8Ki Mar 20, 2022

nagisa Mar 20, 2022

estebank Mar 22, 2022

estebank Aug 25, 2022

nagisa Mar 20, 2022

nagisa Mar 20, 2022

nagisa Mar 20, 2022

nagisa Mar 20, 2022

nagisa Mar 20, 2022

nagisa commented Mar 20, 2022

nagisa commented Mar 20, 2022

estebank commented Mar 22, 2022

TaKO8Ki commented Mar 22, 2022

apiraino commented Apr 7, 2022

bors commented Apr 28, 2022

	"the enum cannot have a struct field declaration",
	"expected an `enum` variant, found a field",

	"consider using `struct` instead of `enum`",
	"consider defining a `struct` or an `union` instead of an `enum`",

Suggest using an appropriate keyword for struct and enum #94996

Suggest using an appropriate keyword for struct and enum #94996

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TaKO8Ki commented Mar 16, 2022

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nagisa commented Mar 20, 2022

nagisa commented Mar 20, 2022

estebank commented Mar 22, 2022

TaKO8Ki commented Mar 22, 2022

apiraino commented Apr 7, 2022

bors commented Apr 28, 2022

Suggest using an appropriate keyword for `struct` and `enum` #94996

Suggest using an appropriate keyword for `struct` and `enum` #94996