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gurrygurry
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Emit suggestions when equality constraints are wrongly used
1 parent 76cf07d commit f7ebad4

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17 files changed

+707
-29
lines changed

17 files changed

+707
-29
lines changed

‎compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

+109-6
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,7 @@ use rustc_hir::def::{DefKind, Res};
1717
use rustc_hir::def_id::{DefId, LocalDefId};
1818
use rustc_infer::traits::FulfillmentError;
1919
use rustc_middle::query::Key;
20+
use rustc_middle::ty::GenericParamDefKind;
2021
use rustc_middle::ty::{self, suggest_constraining_type_param};
2122
use rustc_middle::ty::{AdtDef, Ty, TyCtxt, TypeVisitableExt};
2223
use rustc_middle::ty::{Binder, TraitRef};
@@ -1200,12 +1201,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
12001201
/// Emits an error regarding forbidden type binding associations
12011202
pub fn prohibit_assoc_item_binding(
12021203
tcx: TyCtxt<'_>,
1203-
span: Span,
1204-
segment: Option<(&hir::PathSegment<'_>, Span)>,
1204+
binding: &hir::TypeBinding<'_>,
1205+
segment: Option<(DefId, &hir::PathSegment<'_>, Span)>,
12051206
) -> ErrorGuaranteed {
1206-
tcx.dcx().emit_err(AssocTypeBindingNotAllowed {
1207-
span,
1208-
fn_trait_expansion: if let Some((segment, span)) = segment
1207+
let mut err = tcx.dcx().create_err(AssocTypeBindingNotAllowed {
1208+
span: binding.span,
1209+
fn_trait_expansion: if let Some((_, segment, span)) = segment
12091210
&& segment.args().parenthesized == hir::GenericArgsParentheses::ParenSugar
12101211
{
12111212
Some(ParenthesizedFnTraitExpansion {
@@ -1215,7 +1216,109 @@ pub fn prohibit_assoc_item_binding(
12151216
} else {
12161217
None
12171218
},
1218-
})
1219+
});
1220+
1221+
// Emit a suggestion to turn the assoc item binding into a generic arg
1222+
// if the relevant item has a generic param whose name matches the binding name;
1223+
// otherwise suggest the removal of the binding.
1224+
if let Some((def_id, segment, _)) = segment
1225+
&& segment.args().parenthesized == hir::GenericArgsParentheses::No
1226+
&& let hir::TypeBindingKind::Equality { term } = binding.kind
1227+
{
1228+
// Suggests removal of the offending binding
1229+
let suggest_removal = |e: &mut Diag<'_>| {
1230+
let bindings = segment.args().bindings;
1231+
let args = segment.args().args;
1232+
let binding_span = binding.span;
1233+
1234+
// Compute the span to remove based on the position
1235+
// of the binding. We do that as follows:
1236+
// 1. Find the index of the binding in the list of bindings
1237+
// 2. Locate the spans preceding and following the binding.
1238+
// If it's the first binding the preceding span would be
1239+
// that of the last arg
1240+
// 3. Using this information work out whether the span
1241+
// to remove will start from the end of the preceding span,
1242+
// the start of the next span or will simply be the
1243+
// span encomassing everything within the generics brackets
1244+
1245+
let Some(binding_index) = bindings.iter().position(|b| b.hir_id == binding.hir_id)
1246+
else {
1247+
bug!("a type binding exists but its HIR ID not found in generics");
1248+
};
1249+
1250+
let preceding_span = if binding_index > 0 {
1251+
Some(bindings[binding_index - 1].span)
1252+
} else {
1253+
args.last().map(|a| a.span())
1254+
};
1255+
1256+
let next_span = if binding_index < bindings.len() - 1 {
1257+
Some(bindings[binding_index + 1].span)
1258+
} else {
1259+
None
1260+
};
1261+
1262+
let removal_span = match (preceding_span, next_span) {
1263+
(Some(prec), _) => binding_span.with_lo(prec.hi()),
1264+
(None, Some(next)) => binding_span.with_hi(next.lo()),
1265+
(None, None) => {
1266+
let Some(generics_span) = segment.args().span_ext() else {
1267+
bug!("a type binding exists but generic span is empty");
1268+
};
1269+
1270+
generics_span
1271+
}
1272+
};
1273+
1274+
// Now emit the suggestion
1275+
if let Ok(suggestion) = tcx.sess.source_map().span_to_snippet(removal_span) {
1276+
e.span_suggestion_verbose(
1277+
removal_span,
1278+
"consider removing this type binding",
1279+
suggestion,
1280+
Applicability::MaybeIncorrect,
1281+
);
1282+
}
1283+
};
1284+
1285+
// Suggest replacing the associated item binding with a generic argument.
1286+
// i.e., replacing `<..., T = A, ...>` with `<..., A, ...>`.
1287+
let suggest_direct_use = |e: &mut Diag<'_>, sp: Span| {
1288+
if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(sp) {
1289+
e.span_suggestion_verbose(
1290+
binding.span,
1291+
format!("to use `{snippet}` as a generic argument specify it directly"),
1292+
snippet,
1293+
Applicability::MaybeIncorrect,
1294+
);
1295+
}
1296+
};
1297+
1298+
// Check if the type has a generic param with the
1299+
// same name as the assoc type name in type binding
1300+
let generics = tcx.generics_of(def_id);
1301+
let matching_param =
1302+
generics.params.iter().find(|p| p.name.as_str() == binding.ident.as_str());
1303+
1304+
// Now emit the appropriate suggestion
1305+
if let Some(matching_param) = matching_param {
1306+
match (&matching_param.kind, term) {
1307+
(GenericParamDefKind::Type { .. }, hir::Term::Ty(ty)) => {
1308+
suggest_direct_use(&mut err, ty.span);
1309+
}
1310+
(GenericParamDefKind::Const { .. }, hir::Term::Const(c)) => {
1311+
let span = tcx.hir().span(c.hir_id);
1312+
suggest_direct_use(&mut err, span);
1313+
}
1314+
_ => suggest_removal(&mut err),
1315+
}
1316+
} else {
1317+
suggest_removal(&mut err);
1318+
}
1319+
}
1320+
1321+
err.emit()
12191322
}
12201323

12211324
pub(crate) fn fn_trait_to_string(

‎compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -454,7 +454,7 @@ pub(crate) fn check_generic_arg_count(
454454
if gen_pos != GenericArgPosition::Type
455455
&& let Some(b) = gen_args.bindings.first()
456456
{
457-
prohibit_assoc_item_binding(tcx, b.span, None);
457+
prohibit_assoc_item_binding(tcx, b, None);
458458
}
459459

460460
let explicit_late_bound =

‎compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

+4-4
Original file line numberDiff line numberDiff line change
@@ -322,7 +322,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
322322
ty::BoundConstness::NotConst,
323323
);
324324
if let Some(b) = item_segment.args().bindings.first() {
325-
prohibit_assoc_item_binding(self.tcx(), b.span, Some((item_segment, span)));
325+
prohibit_assoc_item_binding(self.tcx(), b, Some((def_id, item_segment, span)));
326326
}
327327
args
328328
}
@@ -619,7 +619,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
619619
ty::BoundConstness::NotConst,
620620
);
621621
if let Some(b) = item_segment.args().bindings.first() {
622-
prohibit_assoc_item_binding(self.tcx(), b.span, Some((item_segment, span)));
622+
prohibit_assoc_item_binding(self.tcx(), b, Some((item_def_id, item_segment, span)));
623623
}
624624
args
625625
}
@@ -764,7 +764,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
764764
constness,
765765
);
766766
if let Some(b) = trait_segment.args().bindings.first() {
767-
prohibit_assoc_item_binding(self.tcx(), b.span, Some((trait_segment, span)));
767+
prohibit_assoc_item_binding(self.tcx(), b, Some((trait_def_id, trait_segment, span)));
768768
}
769769
ty::TraitRef::new(self.tcx(), trait_def_id, generic_args)
770770
}
@@ -1556,7 +1556,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
15561556
for segment in segments {
15571557
// Only emit the first error to avoid overloading the user with error messages.
15581558
if let Some(b) = segment.args().bindings.first() {
1559-
return Err(prohibit_assoc_item_binding(self.tcx(), b.span, None));
1559+
return Err(prohibit_assoc_item_binding(self.tcx(), b, None));
15601560
}
15611561
}
15621562

‎tests/rustdoc-ui/invalid_associated_const.stderr

+9
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,11 @@ error[E0229]: associated type bindings are not allowed here
33
|
44
LL | type A: S<C<X = 0i32> = 34>;
55
| ^^^^^^^^ associated type not allowed here
6+
|
7+
help: consider removing this type binding
8+
|
9+
LL | type A: S<C<X = 0i32> = 34>;
10+
| ~~~~~~~~~~
611

712
error[E0229]: associated type bindings are not allowed here
813
--> $DIR/invalid_associated_const.rs:4:17
@@ -11,6 +16,10 @@ LL | type A: S<C<X = 0i32> = 34>;
1116
| ^^^^^^^^ associated type not allowed here
1217
|
1318
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
19+
help: consider removing this type binding
20+
|
21+
LL | type A: S<C<X = 0i32> = 34>;
22+
| ~~~~~~~~~~
1423

1524
error: aborting due to 2 previous errors
1625

‎tests/rustdoc-ui/issue-102467.stderr

+9
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,11 @@ error[E0229]: associated type bindings are not allowed here
33
|
44
LL | type A: S<C<X = 0i32> = 34>;
55
| ^^^^^^^^ associated type not allowed here
6+
|
7+
help: consider removing this type binding
8+
|
9+
LL | type A: S<C<X = 0i32> = 34>;
10+
| ~~~~~~~~~~
611

712
error[E0229]: associated type bindings are not allowed here
813
--> $DIR/issue-102467.rs:7:17
@@ -11,6 +16,10 @@ LL | type A: S<C<X = 0i32> = 34>;
1116
| ^^^^^^^^ associated type not allowed here
1217
|
1318
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
19+
help: consider removing this type binding
20+
|
21+
LL | type A: S<C<X = 0i32> = 34>;
22+
| ~~~~~~~~~~
1423

1524
error: aborting due to 2 previous errors
1625

‎tests/ui/associated-consts/issue-102335-const.stderr

+9
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,11 @@ error[E0229]: associated type bindings are not allowed here
33
|
44
LL | type A: S<C<X = 0i32> = 34>;
55
| ^^^^^^^^ associated type not allowed here
6+
|
7+
help: consider removing this type binding
8+
|
9+
LL | type A: S<C<X = 0i32> = 34>;
10+
| ~~~~~~~~~~
611

712
error[E0229]: associated type bindings are not allowed here
813
--> $DIR/issue-102335-const.rs:4:17
@@ -11,6 +16,10 @@ LL | type A: S<C<X = 0i32> = 34>;
1116
| ^^^^^^^^ associated type not allowed here
1217
|
1318
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
19+
help: consider removing this type binding
20+
|
21+
LL | type A: S<C<X = 0i32> = 34>;
22+
| ~~~~~~~~~~
1423

1524
error: aborting due to 2 previous errors
1625

‎tests/ui/associated-type-bounds/issue-102335-ty.rs

+7-1
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,11 @@
11
trait T {
2-
type A: S<C<i32 = u32> = ()>;
2+
type A: S<C<i32 = u32> = ()>; // Just one erroneous equality constraint
3+
//~^ ERROR associated type bindings are not allowed here
4+
//~| ERROR associated type bindings are not allowed here
5+
}
6+
7+
trait T2 {
8+
type A: S<C<i32 = u32, X = i32> = ()>; // More than one erroneous equality constraints
39
//~^ ERROR associated type bindings are not allowed here
410
//~| ERROR associated type bindings are not allowed here
511
}

‎tests/ui/associated-type-bounds/issue-102335-ty.stderr

+35-3
Original file line numberDiff line numberDiff line change
@@ -1,17 +1,49 @@
11
error[E0229]: associated type bindings are not allowed here
22
--> $DIR/issue-102335-ty.rs:2:17
33
|
4-
LL | type A: S<C<i32 = u32> = ()>;
4+
LL | type A: S<C<i32 = u32> = ()>; // Just one erroneous equality constraint
55
| ^^^^^^^^^ associated type not allowed here
6+
|
7+
help: consider removing this type binding
8+
|
9+
LL | type A: S<C<i32 = u32> = ()>; // Just one erroneous equality constraint
10+
| ~~~~~~~~~~~
611

712
error[E0229]: associated type bindings are not allowed here
813
--> $DIR/issue-102335-ty.rs:2:17
914
|
10-
LL | type A: S<C<i32 = u32> = ()>;
15+
LL | type A: S<C<i32 = u32> = ()>; // Just one erroneous equality constraint
16+
| ^^^^^^^^^ associated type not allowed here
17+
|
18+
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
19+
help: consider removing this type binding
20+
|
21+
LL | type A: S<C<i32 = u32> = ()>; // Just one erroneous equality constraint
22+
| ~~~~~~~~~~~
23+
24+
error[E0229]: associated type bindings are not allowed here
25+
--> $DIR/issue-102335-ty.rs:8:17
26+
|
27+
LL | type A: S<C<i32 = u32, X = i32> = ()>; // More than one erroneous equality constraints
28+
| ^^^^^^^^^ associated type not allowed here
29+
|
30+
help: consider removing this type binding
31+
|
32+
LL | type A: S<C<i32 = u32, X = i32> = ()>; // More than one erroneous equality constraints
33+
| ~~~~~~~~~~
34+
35+
error[E0229]: associated type bindings are not allowed here
36+
--> $DIR/issue-102335-ty.rs:8:17
37+
|
38+
LL | type A: S<C<i32 = u32, X = i32> = ()>; // More than one erroneous equality constraints
1139
| ^^^^^^^^^ associated type not allowed here
1240
|
1341
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
42+
help: consider removing this type binding
43+
|
44+
LL | type A: S<C<i32 = u32, X = i32> = ()>; // More than one erroneous equality constraints
45+
| ~~~~~~~~~~
1446

15-
error: aborting due to 2 previous errors
47+
error: aborting due to 4 previous errors
1648

1749
For more information about this error, try `rustc --explain E0229`.

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