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Rollup merge of #87775 - Kobzol:single-associated-item-hint, r=oli-obk
Add hint for unresolved associated trait items if the trait has a single item This PR introduces a special-cased hint for unresolved trait items paths. It is shown if: - the path was not resolved to any existing trait item - and no existing trait item's name was reasonably close with regard to edit distance - and the trait only has a single item in the corresponding namespace I didn't know where I should put tests, therefore so far I just managed to bless two existing tests. I would be glad for hints where should tests for a hint like this be created, how should they be named (with reference to the original issue?) and what tests should I create (is it enough to test it just for types? or create separate tests also for functions and constants?). It could also be turned into a machine applicable suggestion I suppose. This is my first `rustc` PR, so please go easy on me :) Fixes: #87638
2 parents 3b0e797 + d0d4947 commit 8ee962f

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‎compiler/rustc_resolve/src/diagnostics.rs

Lines changed: 43 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -38,14 +38,25 @@ crate type Suggestion = (Vec<(Span, String)>, String, Applicability);
3838
/// similarly named label and whether or not it is reachable.
3939
crate type LabelSuggestion = (Ident, bool);
4040

41+
crate enum SuggestionTarget {
42+
/// The target has a similar name as the name used by the programmer (probably a typo)
43+
SimilarlyNamed,
44+
/// The target is the only valid item that can be used in the corresponding context
45+
SingleItem,
46+
}
47+
4148
crate struct TypoSuggestion {
4249
pub candidate: Symbol,
4350
pub res: Res,
51+
pub target: SuggestionTarget,
4452
}
4553

4654
impl TypoSuggestion {
47-
crate fn from_res(candidate: Symbol, res: Res) -> TypoSuggestion {
48-
TypoSuggestion { candidate, res }
55+
crate fn typo_from_res(candidate: Symbol, res: Res) -> TypoSuggestion {
56+
Self { candidate, res, target: SuggestionTarget::SimilarlyNamed }
57+
}
58+
crate fn single_item_from_res(candidate: Symbol, res: Res) -> TypoSuggestion {
59+
Self { candidate, res, target: SuggestionTarget::SingleItem }
4960
}
5061
}
5162

@@ -80,7 +91,7 @@ impl<'a> Resolver<'a> {
8091
if let Some(binding) = resolution.borrow().binding {
8192
let res = binding.res();
8293
if filter_fn(res) {
83-
names.push(TypoSuggestion::from_res(key.ident.name, res));
94+
names.push(TypoSuggestion::typo_from_res(key.ident.name, res));
8495
}
8596
}
8697
}
@@ -623,7 +634,7 @@ impl<'a> Resolver<'a> {
623634
.get(&expn_id)
624635
.into_iter()
625636
.flatten()
626-
.map(|ident| TypoSuggestion::from_res(ident.name, res)),
637+
.map(|ident| TypoSuggestion::typo_from_res(ident.name, res)),
627638
);
628639
}
629640
}
@@ -642,7 +653,7 @@ impl<'a> Resolver<'a> {
642653
suggestions.extend(
643654
ext.helper_attrs
644655
.iter()
645-
.map(|name| TypoSuggestion::from_res(*name, res)),
656+
.map(|name| TypoSuggestion::typo_from_res(*name, res)),
646657
);
647658
}
648659
}
@@ -652,8 +663,10 @@ impl<'a> Resolver<'a> {
652663
if let MacroRulesScope::Binding(macro_rules_binding) = macro_rules_scope.get() {
653664
let res = macro_rules_binding.binding.res();
654665
if filter_fn(res) {
655-
suggestions
656-
.push(TypoSuggestion::from_res(macro_rules_binding.ident.name, res))
666+
suggestions.push(TypoSuggestion::typo_from_res(
667+
macro_rules_binding.ident.name,
668+
res,
669+
))
657670
}
658671
}
659672
}
@@ -671,15 +684,15 @@ impl<'a> Resolver<'a> {
671684
suggestions.extend(
672685
this.registered_attrs
673686
.iter()
674-
.map(|ident| TypoSuggestion::from_res(ident.name, res)),
687+
.map(|ident| TypoSuggestion::typo_from_res(ident.name, res)),
675688
);
676689
}
677690
}
678691
Scope::MacroUsePrelude => {
679692
suggestions.extend(this.macro_use_prelude.iter().filter_map(
680693
|(name, binding)| {
681694
let res = binding.res();
682-
filter_fn(res).then_some(TypoSuggestion::from_res(*name, res))
695+
filter_fn(res).then_some(TypoSuggestion::typo_from_res(*name, res))
683696
},
684697
));
685698
}
@@ -689,22 +702,22 @@ impl<'a> Resolver<'a> {
689702
suggestions.extend(
690703
BUILTIN_ATTRIBUTES
691704
.iter()
692-
.map(|(name, ..)| TypoSuggestion::from_res(*name, res)),
705+
.map(|(name, ..)| TypoSuggestion::typo_from_res(*name, res)),
693706
);
694707
}
695708
}
696709
Scope::ExternPrelude => {
697710
suggestions.extend(this.extern_prelude.iter().filter_map(|(ident, _)| {
698711
let res = Res::Def(DefKind::Mod, DefId::local(CRATE_DEF_INDEX));
699-
filter_fn(res).then_some(TypoSuggestion::from_res(ident.name, res))
712+
filter_fn(res).then_some(TypoSuggestion::typo_from_res(ident.name, res))
700713
}));
701714
}
702715
Scope::ToolPrelude => {
703716
let res = Res::NonMacroAttr(NonMacroAttrKind::Tool);
704717
suggestions.extend(
705718
this.registered_tools
706719
.iter()
707-
.map(|ident| TypoSuggestion::from_res(ident.name, res)),
720+
.map(|ident| TypoSuggestion::typo_from_res(ident.name, res)),
708721
);
709722
}
710723
Scope::StdLibPrelude => {
@@ -721,7 +734,7 @@ impl<'a> Resolver<'a> {
721734
Scope::BuiltinTypes => {
722735
suggestions.extend(PrimTy::ALL.iter().filter_map(|prim_ty| {
723736
let res = Res::PrimTy(*prim_ty);
724-
filter_fn(res).then_some(TypoSuggestion::from_res(prim_ty.name(), res))
737+
filter_fn(res).then_some(TypoSuggestion::typo_from_res(prim_ty.name(), res))
725738
}))
726739
}
727740
}
@@ -993,20 +1006,31 @@ impl<'a> Resolver<'a> {
9931006
// | ^
9941007
return false;
9951008
}
1009+
let prefix = match suggestion.target {
1010+
SuggestionTarget::SimilarlyNamed => "similarly named ",
1011+
SuggestionTarget::SingleItem => "",
1012+
};
1013+
9961014
err.span_label(
9971015
self.session.source_map().guess_head_span(def_span),
9981016
&format!(
999-
"similarly named {} `{}` defined here",
1017+
"{}{} `{}` defined here",
1018+
prefix,
10001019
suggestion.res.descr(),
10011020
suggestion.candidate.as_str(),
10021021
),
10031022
);
10041023
}
1005-
let msg = format!(
1006-
"{} {} with a similar name exists",
1007-
suggestion.res.article(),
1008-
suggestion.res.descr()
1009-
);
1024+
let msg = match suggestion.target {
1025+
SuggestionTarget::SimilarlyNamed => format!(
1026+
"{} {} with a similar name exists",
1027+
suggestion.res.article(),
1028+
suggestion.res.descr()
1029+
),
1030+
SuggestionTarget::SingleItem => {
1031+
format!("maybe you meant this {}", suggestion.res.descr())
1032+
}
1033+
};
10101034
err.span_suggestion(
10111035
span,
10121036
&msg,

‎compiler/rustc_resolve/src/late/diagnostics.rs

Lines changed: 45 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -541,6 +541,10 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
541541
}
542542
_ => {}
543543
}
544+
545+
// If the trait has a single item (which wasn't matched by Levenshtein), suggest it
546+
let suggestion = self.get_single_associated_item(&path, span, &source, is_expected);
547+
self.r.add_typo_suggestion(&mut err, suggestion, ident_span);
544548
}
545549
if fallback {
546550
// Fallback label.
@@ -585,6 +589,40 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
585589
(err, candidates)
586590
}
587591

592+
fn get_single_associated_item(
593+
&mut self,
594+
path: &[Segment],
595+
span: Span,
596+
source: &PathSource<'_>,
597+
filter_fn: &impl Fn(Res) -> bool,
598+
) -> Option<TypoSuggestion> {
599+
if let crate::PathSource::TraitItem(_) = source {
600+
let mod_path = &path[..path.len() - 1];
601+
if let PathResult::Module(ModuleOrUniformRoot::Module(module)) =
602+
self.resolve_path(mod_path, None, false, span, CrateLint::No)
603+
{
604+
let resolutions = self.r.resolutions(module).borrow();
605+
let targets: Vec<_> =
606+
resolutions
607+
.iter()
608+
.filter_map(|(key, resolution)| {
609+
resolution.borrow().binding.map(|binding| binding.res()).and_then(
610+
|res| if filter_fn(res) { Some((key, res)) } else { None },
611+
)
612+
})
613+
.collect();
614+
if targets.len() == 1 {
615+
let target = targets[0];
616+
return Some(TypoSuggestion::single_item_from_res(
617+
target.0.ident.name,
618+
target.1,
619+
));
620+
}
621+
}
622+
}
623+
None
624+
}
625+
588626
/// Given `where <T as Bar>::Baz: String`, suggest `where T: Bar<Baz = String>`.
589627
fn restrict_assoc_type_in_where_clause(
590628
&mut self,
@@ -1208,7 +1246,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
12081246
// Locals and type parameters
12091247
for (ident, &res) in &rib.bindings {
12101248
if filter_fn(res) {
1211-
names.push(TypoSuggestion::from_res(ident.name, res));
1249+
names.push(TypoSuggestion::typo_from_res(ident.name, res));
12121250
}
12131251
}
12141252
// Items in scope
@@ -1231,7 +1269,9 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
12311269
);
12321270

12331271
if filter_fn(crate_mod) {
1234-
Some(TypoSuggestion::from_res(ident.name, crate_mod))
1272+
Some(TypoSuggestion::typo_from_res(
1273+
ident.name, crate_mod,
1274+
))
12351275
} else {
12361276
None
12371277
}
@@ -1249,11 +1289,9 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
12491289
}
12501290
// Add primitive types to the mix
12511291
if filter_fn(Res::PrimTy(PrimTy::Bool)) {
1252-
names.extend(
1253-
PrimTy::ALL.iter().map(|prim_ty| {
1254-
TypoSuggestion::from_res(prim_ty.name(), Res::PrimTy(*prim_ty))
1255-
}),
1256-
)
1292+
names.extend(PrimTy::ALL.iter().map(|prim_ty| {
1293+
TypoSuggestion::typo_from_res(prim_ty.name(), Res::PrimTy(*prim_ty))
1294+
}))
12571295
}
12581296
} else {
12591297
// Search in module.

‎src/test/ui/associated-item/issue-87638.fixed

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,22 @@
1+
// run-rustfix
2+
3+
trait Trait {
4+
const FOO: usize;
5+
6+
type Target;
7+
}
8+
9+
struct S;
10+
11+
impl Trait for S {
12+
const FOO: usize = 0;
13+
type Target = ();
14+
}
15+
16+
fn main() {
17+
let _: <S as Trait>::Target; //~ ERROR cannot find associated type `Output` in trait `Trait`
18+
//~^ HELP maybe you meant this associated type
19+
20+
let _ = <S as Trait>::FOO; //~ ERROR cannot find method or associated constant `BAR` in trait `Trait`
21+
//~^ HELP maybe you meant this associated constant
22+
}

‎src/test/ui/associated-item/issue-87638.rs

Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,22 @@
1+
// run-rustfix
2+
3+
trait Trait {
4+
const FOO: usize;
5+
6+
type Target;
7+
}
8+
9+
struct S;
10+
11+
impl Trait for S {
12+
const FOO: usize = 0;
13+
type Target = ();
14+
}
15+
16+
fn main() {
17+
let _: <S as Trait>::Output; //~ ERROR cannot find associated type `Output` in trait `Trait`
18+
//~^ HELP maybe you meant this associated type
19+
20+
let _ = <S as Trait>::BAR; //~ ERROR cannot find method or associated constant `BAR` in trait `Trait`
21+
//~^ HELP maybe you meant this associated constant
22+
}

‎src/test/ui/associated-item/issue-87638.stderr

Lines changed: 27 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,27 @@
1+
error[E0576]: cannot find associated type `Output` in trait `Trait`
2+
--> $DIR/issue-87638.rs:17:26
3+
|
4+
LL | type Target;
5+
| ------------ associated type `Target` defined here
6+
...
7+
LL | let _: <S as Trait>::Output;
8+
| ^^^^^^
9+
| |
10+
| not found in `Trait`
11+
| help: maybe you meant this associated type: `Target`
12+
13+
error[E0576]: cannot find method or associated constant `BAR` in trait `Trait`
14+
--> $DIR/issue-87638.rs:20:27
15+
|
16+
LL | const FOO: usize;
17+
| ----------------- associated constant `FOO` defined here
18+
...
19+
LL | let _ = <S as Trait>::BAR;
20+
| ^^^
21+
| |
22+
| not found in `Trait`
23+
| help: maybe you meant this associated constant: `FOO`
24+
25+
error: aborting due to 2 previous errors
26+
27+
For more information about this error, try `rustc --explain E0576`.

‎src/test/ui/associated-types/issue-22037.stderr

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,13 @@
11
error[E0576]: cannot find associated type `X` in trait `A`
22
--> $DIR/issue-22037.rs:3:33
33
|
4+
LL | type Output;
5+
| ------------ associated type `Output` defined here
46
LL | fn a(&self) -> <Self as A>::X;
5-
| ^ not found in `A`
7+
| ^
8+
| |
9+
| not found in `A`
10+
| help: maybe you meant this associated type: `Output`
611

712
error: aborting due to previous error
813

‎src/test/ui/issues/issue-19883.stderr

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,8 +1,14 @@
11
error[E0576]: cannot find associated type `Dst` in trait `From`
22
--> $DIR/issue-19883.rs:9:30
33
|
4+
LL | type Output;
5+
| ------------ associated type `Output` defined here
6+
...
47
LL | <Dst as From<Self>>::Dst
5-
| ^^^ not found in `From`
8+
| ^^^
9+
| |
10+
| not found in `From`
11+
| help: maybe you meant this associated type: `Output`
612

713
error: aborting due to previous error
814

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