On E0308 caused by cloning a reference due to missing bounds, account for derive
On type errors where the difference is expecting an owned type and getting a reference, if the expression is a `.clone()` call and the type is annotated with `#[derive(Clone)]`, we now explain implicit bounds and suggest manually implementing `Clone`.
```
error[E0308]: mismatched types
--> $DIR/derive-implicit-bound-on-clone.rs:10:5
|
LL | fn clone_me<T, K>(x: &ContainsRc<T, K>) -> ContainsRc<T, K> {
| ---------------- expected `ContainsRc<T, K>` because of return type
LL | x.clone()
| ^^^^^^^^^ expected `ContainsRc<T, K>`, found `&ContainsRc<T, K>`
|
= note: expected struct `ContainsRc<_, _>`
found reference `&ContainsRc<_, _>`
note: `ContainsRc<T, K>` does not implement `Clone`, so `&ContainsRc<T, K>` was cloned instead
--> $DIR/derive-implicit-bound-on-clone.rs:10:5
|
LL | x.clone()
| ^
help: `Clone` is not implemented because the some trait bounds could not be satisfied
--> $DIR/derive-implicit-bound-on-clone.rs:5:19
|
LL | #[derive(Clone)]
| ----- in this derive macro expansion
LL | struct ContainsRc<T, K> {
| ^ ^ derive introduces an implicit unsatisfied trait bound `K: Clone`
| |
| derive introduces an implicit unsatisfied trait bound `T: Clone`
= help: consider manually implementing `Clone` to avoid the implict type parameter bounds
```
This commit is contained in:
Esteban Küber
parent
b88fb8a0b0
commit
085da0cee4
5 changed files with 166 additions and 14 deletions
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@ -1932,25 +1932,96 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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None,
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);
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} else {
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let mut suggest_derive = true;
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if let Some(errors) =
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self.type_implements_trait_shallow(clone_trait_did, expected_ty, self.param_env)
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{
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let manually_impl = "consider manually implementing `Clone` to avoid the \
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implict type parameter bounds";
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match &errors[..] {
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[] => {}
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[error] => {
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diag.help(format!(
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"`Clone` is not implemented because the trait bound `{}` is \
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not satisfied",
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error.obligation.predicate,
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));
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// diag.note("{error:#?}");
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// diag.note(format!("{:#?} {:#?} {:#?}", error.obligation, error.obligation.cause, error.obligation.cause.code()));
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let msg = "`Clone` is not implemented because a trait bound is not \
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satisfied";
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if let traits::ObligationCauseCode::ImplDerived(data) =
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error.obligation.cause.code()
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{
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let mut span: MultiSpan = data.span.into();
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if self.tcx.is_automatically_derived(data.impl_or_alias_def_id) {
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span.push_span_label(
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data.span,
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format!(
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"derive introduces an implicit `{}` bound",
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error.obligation.predicate
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),
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);
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}
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diag.span_help(span, msg);
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if self.tcx.is_automatically_derived(data.impl_or_alias_def_id)
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&& data.impl_or_alias_def_id.is_local()
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{
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diag.help(manually_impl);
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suggest_derive = false;
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}
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} else {
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diag.help(msg);
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}
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}
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_ => {
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diag.help(format!(
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"`Clone` is not implemented because the following trait bounds \
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could not be satisfied: {}",
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listify(&errors, |e| format!("`{}`", e.obligation.predicate))
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.unwrap(),
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));
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let unsatisfied_bounds: Vec<_> = errors
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.iter()
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.filter_map(|error| match error.obligation.cause.code() {
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traits::ObligationCauseCode::ImplDerived(data) => {
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let pre = if self
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.tcx
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.is_automatically_derived(data.impl_or_alias_def_id)
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{
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"derive introduces an implicit "
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} else {
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""
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};
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Some((
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data.span,
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format!(
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"{pre}unsatisfied trait bound `{}`",
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error.obligation.predicate
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),
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))
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}
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_ => None,
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})
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.collect();
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let msg = "`Clone` is not implemented because the some trait bounds \
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could not be satisfied";
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if errors.len() == unsatisfied_bounds.len() {
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let mut unsatisfied_bounds_spans: MultiSpan = unsatisfied_bounds
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.iter()
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.map(|(span, _)| *span)
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.collect::<Vec<Span>>()
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.into();
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for (span, label) in unsatisfied_bounds {
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unsatisfied_bounds_spans.push_span_label(span, label);
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}
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diag.span_help(unsatisfied_bounds_spans, msg);
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if errors.iter().all(|error| match error.obligation.cause.code() {
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traits::ObligationCauseCode::ImplDerived(data) => {
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self.tcx.is_automatically_derived(data.impl_or_alias_def_id)
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&& data.impl_or_alias_def_id.is_local()
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}
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_ => false,
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}) {
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diag.help(manually_impl);
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suggest_derive = false;
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}
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} else {
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diag.help(format!(
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"{msg}: {}",
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listify(&errors, |e| format!("`{}`", e.obligation.predicate))
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.unwrap(),
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));
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}
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}
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}
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for error in errors {
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@ -1968,7 +2039,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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}
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}
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}
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self.suggest_derive(diag, &vec![(trait_ref.upcast(self.tcx), None, None)]);
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if suggest_derive {
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self.suggest_derive(diag, &vec![(trait_ref.upcast(self.tcx), None, None)]);
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}
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}
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}
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}
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@ -13,7 +13,8 @@ note: `HashSet<Day>` does not implement `Clone`, so `&HashSet<Day>` was cloned i
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LL | let mut x: HashSet<Day> = v.clone();
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| ^
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= help: `Clone` is not implemented because the trait bound `Day: Clone` is not satisfied
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help: `Clone` is not implemented because a trait bound is not satisfied
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--> $SRC_DIR/std/src/collections/hash/set.rs:LL:COL
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help: consider annotating `Day` with `#[derive(Clone)]`
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LL + #[derive(Clone)]
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@ -13,7 +13,8 @@ note: `HashSet<Day>` does not implement `Clone`, so `&HashSet<Day>` was cloned i
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LL | let mut x: HashSet<Day> = v.clone();
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| ^
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= help: `Clone` is not implemented because the trait bound `Day: Clone` is not satisfied
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help: `Clone` is not implemented because a trait bound is not satisfied
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--> $SRC_DIR/std/src/collections/hash/set.rs:LL:COL
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help: consider annotating `Day` with `#[derive(Clone)]`
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LL + #[derive(Clone)]
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24
tests/ui/traits/derive-implicit-bound-on-clone.rs
Normal file
24
tests/ui/traits/derive-implicit-bound-on-clone.rs
Normal file
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@ -0,0 +1,24 @@
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// Issue #146515
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use std::rc::Rc;
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#[derive(Clone)]
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struct ContainsRc<T, K> { //~ HELP `Clone` is not implemented
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value: Rc<(T, K)>,
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}
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fn clone_me<T, K>(x: &ContainsRc<T, K>) -> ContainsRc<T, K> {
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x.clone() //~ ERROR E0308
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//~^ HELP consider manually implementing `Clone`
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}
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#[derive(Clone)]
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struct ContainsRcSingle<T> { //~ HELP `Clone` is not implemented
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value: Rc<T>,
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}
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fn clone_me_single<T>(x: &ContainsRcSingle<T>) -> ContainsRcSingle<T> {
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x.clone() //~ ERROR E0308
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//~^ HELP consider manually implementing `Clone`
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}
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fn main() {}
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53
tests/ui/traits/derive-implicit-bound-on-clone.stderr
Normal file
53
tests/ui/traits/derive-implicit-bound-on-clone.stderr
Normal file
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@ -0,0 +1,53 @@
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error[E0308]: mismatched types
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--> $DIR/derive-implicit-bound-on-clone.rs:10:5
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LL | fn clone_me<T, K>(x: &ContainsRc<T, K>) -> ContainsRc<T, K> {
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| ---------------- expected `ContainsRc<T, K>` because of return type
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LL | x.clone()
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| ^^^^^^^^^ expected `ContainsRc<T, K>`, found `&ContainsRc<T, K>`
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|
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= note: expected struct `ContainsRc<_, _>`
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found reference `&ContainsRc<_, _>`
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note: `ContainsRc<T, K>` does not implement `Clone`, so `&ContainsRc<T, K>` was cloned instead
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--> $DIR/derive-implicit-bound-on-clone.rs:10:5
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LL | x.clone()
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| ^
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help: `Clone` is not implemented because the some trait bounds could not be satisfied
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--> $DIR/derive-implicit-bound-on-clone.rs:5:19
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|
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LL | #[derive(Clone)]
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| ----- in this derive macro expansion
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LL | struct ContainsRc<T, K> {
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| ^ ^ derive introduces an implicit unsatisfied trait bound `K: Clone`
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| |
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| derive introduces an implicit unsatisfied trait bound `T: Clone`
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= help: consider manually implementing `Clone` to avoid the implict type parameter bounds
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error[E0308]: mismatched types
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--> $DIR/derive-implicit-bound-on-clone.rs:20:5
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LL | fn clone_me_single<T>(x: &ContainsRcSingle<T>) -> ContainsRcSingle<T> {
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| ------------------- expected `ContainsRcSingle<T>` because of return type
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LL | x.clone()
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| ^^^^^^^^^ expected `ContainsRcSingle<T>`, found `&ContainsRcSingle<T>`
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|
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= note: expected struct `ContainsRcSingle<_>`
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found reference `&ContainsRcSingle<_>`
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note: `ContainsRcSingle<T>` does not implement `Clone`, so `&ContainsRcSingle<T>` was cloned instead
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--> $DIR/derive-implicit-bound-on-clone.rs:20:5
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LL | x.clone()
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| ^
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help: `Clone` is not implemented because a trait bound is not satisfied
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--> $DIR/derive-implicit-bound-on-clone.rs:15:25
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|
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LL | #[derive(Clone)]
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| ----- in this derive macro expansion
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LL | struct ContainsRcSingle<T> {
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| ^ derive introduces an implicit `T: Clone` bound
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= help: consider manually implementing `Clone` to avoid the implict type parameter bounds
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0308`.
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