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Account for non-overlapping unmet trait bounds in suggestion

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When a method not found on a type parameter could have been provided by any
of multiple traits, suggest each trait individually, instead of a single
suggestion to restrict the type parameter with *all* of them.

Before:

```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
  --> $DIR/method-on-unbounded-type-param.rs:5:10
   |
LL |     (&a).cmp(&b)
   |          ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `T: Ord`
           which is required by `&T: Ord`
           `&T: Iterator`
           which is required by `&mut &T: Iterator`
           `T: Iterator`
           which is required by `&mut T: Iterator`
help: consider restricting the type parameters to satisfy the trait bounds
   |
LL | fn g<T>(a: T, b: T) -> std::cmp::Ordering where T: Iterator, T: Ord {
   |                                           +++++++++++++++++++++++++
```

After:

```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
  --> $DIR/method-on-unbounded-type-param.rs:5:10
   |
LL |     (&a).cmp(&b)
   |          ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
   |
   = note: the following trait bounds were not satisfied:
           `T: Ord`
           which is required by `&T: Ord`
           `&T: Iterator`
           which is required by `&mut &T: Iterator`
           `T: Iterator`
           which is required by `&mut T: Iterator`
   = help: items from traits can only be used if the type parameter is bounded by the trait
help: the following traits define an item `cmp`, perhaps you need to restrict type parameter `T` with one of them:
   |
LL | fn g<T: Ord>(a: T, b: T) -> std::cmp::Ordering {
   |       +++++
LL | fn g<T: Iterator>(a: T, b: T) -> std::cmp::Ordering {
   |       ++++++++++
```

Fix #108428.
This commit is contained in:
Esteban Küber 2024-01-30 18:10:12 +00:00
parent 9ccc77036a
commit 5c414094ac
9 changed files with 62 additions and 52 deletions
Download patch file Download diff file Expand all files Collapse all files

58
compiler/rustc_hir_typeck/src/method/suggest.rs
View file

@ -540,6 +540,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let mut bound_spans: SortedMap<Span, Vec<String>> = Default::default();
let mut restrict_type_params = false;
let mut suggested_derive = false;
let mut unsatisfied_bounds = false;
if item_name.name == sym::count && self.is_slice_ty(rcvr_ty, span) {
let msg = "consider using `len` instead";
@ -927,20 +928,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
.enumerate()
.collect::<Vec<(usize, String)>>();
for ((span, add_where_or_comma), obligations) in type_params.into_iter() {
restrict_type_params = true;
// #74886: Sort here so that the output is always the same.
let obligations = obligations.into_sorted_stable_ord();
err.span_suggestion_verbose(
span,
format!(
"consider restricting the type parameter{s} to satisfy the \
trait bound{s}",
s = pluralize!(obligations.len())
),
format!("{} {}", add_where_or_comma, obligations.join(", ")),
Applicability::MaybeIncorrect,
);
if !matches!(rcvr_ty.peel_refs().kind(), ty::Param(_)) {
for ((span, add_where_or_comma), obligations) in type_params.into_iter() {
restrict_type_params = true;
// #74886: Sort here so that the output is always the same.
let obligations = obligations.into_sorted_stable_ord();
err.span_suggestion_verbose(
span,
format!(
"consider restricting the type parameter{s} to satisfy the trait \
bound{s}",
s = pluralize!(obligations.len())
),
format!("{} {}", add_where_or_comma, obligations.join(", ")),
Applicability::MaybeIncorrect,
);
}
}
bound_list.sort_by(|(_, a), (_, b)| a.cmp(b)); // Sort alphabetically.
@ -988,7 +991,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
"the following trait bounds were not satisfied:\n{bound_list}"
));
}
self.suggest_derive(&mut err, unsatisfied_predicates);
suggested_derive = self.suggest_derive(&mut err, unsatisfied_predicates);
unsatisfied_bounds = true;
}
@ -1211,7 +1214,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
);
}
if rcvr_ty.is_numeric() && rcvr_ty.is_fresh() || restrict_type_params {
if rcvr_ty.is_numeric() && rcvr_ty.is_fresh() || restrict_type_params || suggested_derive {
} else {
self.suggest_traits_to_import(
&mut err,
@ -1221,7 +1224,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
args.map(|args| args.len() + 1),
source,
no_match_data.out_of_scope_traits.clone(),
unsatisfied_predicates,
static_candidates,
unsatisfied_bounds,
expected.only_has_type(self),
@ -2481,7 +2483,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
Option<ty::Predicate<'tcx>>,
Option<ObligationCause<'tcx>>,
)],
) {
) -> bool {
let mut derives = self.note_predicate_source_and_get_derives(err, unsatisfied_predicates);
derives.sort();
derives.dedup();
@ -2506,6 +2508,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
Applicability::MaybeIncorrect,
);
}
!derives_grouped.is_empty()
}
fn note_derefed_ty_has_method(
@ -2708,11 +2711,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
inputs_len: Option<usize>,
source: SelfSource<'tcx>,
valid_out_of_scope_traits: Vec<DefId>,
unsatisfied_predicates: &[(
ty::Predicate<'tcx>,
Option<ty::Predicate<'tcx>>,
Option<ObligationCause<'tcx>>,
)],
static_candidates: &[CandidateSource],
unsatisfied_bounds: bool,
return_type: Option<Ty<'tcx>>,
@ -2977,20 +2975,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
item.visibility(self.tcx).is_public() || info.def_id.is_local()
})
.is_some()
&& (matches!(rcvr_ty.kind(), ty::Param(_))
|| unsatisfied_predicates.iter().all(|(p, _, _)| {
match p.kind().skip_binder() {
// Hide traits if they are present in predicates as they can be fixed without
// having to implement them.
ty::PredicateKind::Clause(ty::ClauseKind::Trait(t)) => {
t.def_id() == info.def_id
}
ty::PredicateKind::Clause(ty::ClauseKind::Projection(p)) => {
p.projection_ty.def_id == info.def_id
}
_ => false,
}
}))
})
.collect::<Vec<_>>();
for span in &arbitrary_rcvr {