bjoernager/rust
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Mention when type parameter could be Clone

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```
error[E0382]: use of moved value: `t`
  --> $DIR/use_of_moved_value_copy_suggestions.rs:7:9
   |
LL | fn duplicate_t<T>(t: T) -> (T, T) {
   |                   - move occurs because `t` has type `T`, which does not implement the `Copy` trait
...
LL |     (t, t)
   |      -  ^ value used here after move
   |      |
   |      value moved here
   |
help: if `T` implemented `Clone`, you could clone the value
  --> $DIR/use_of_moved_value_copy_suggestions.rs:4:16
   |
LL | fn duplicate_t<T>(t: T) -> (T, T) {
   |                ^ consider constraining this type parameter with `Clone`
...
LL |     (t, t)
   |      - you could clone this value
help: consider restricting type parameter `T`
   |
LL | fn duplicate_t<T: Copy>(t: T) -> (T, T) {
   |                 ++++++
```

The `help` is new. On ADTs, we also extend the output with span labels:

```
error[E0507]: cannot move out of static item `FOO`
  --> $DIR/issue-17718-static-move.rs:6:14
   |
LL |     let _a = FOO;
   |              ^^^ move occurs because `FOO` has type `Foo`, which does not implement the `Copy` trait
   |
note: if `Foo` implemented `Clone`, you could clone the value
  --> $DIR/issue-17718-static-move.rs:1:1
   |
LL | struct Foo;
   | ^^^^^^^^^^ consider implementing `Clone` for this type
...
LL |     let _a = FOO;
   |              --- you could clone this value
help: consider borrowing here
   |
LL |     let _a = &FOO;
   |              +
```
This commit is contained in:
Esteban Küber 2024-04-18 22:18:19 +00:00
parent 4aba2c55e6
commit d68f2a6b71
51 changed files with 640 additions and 86 deletions
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47
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
View file

@ -347,7 +347,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
mpi: MovePathIndex,
err: &mut Diag<'tcx>,
in_pattern: &mut bool,
move_spans: UseSpans<'_>,
move_spans: UseSpans<'tcx>,
) {
let move_span = match move_spans {
UseSpans::ClosureUse { capture_kind_span, .. } => capture_kind_span,
@ -491,11 +491,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
..
} = move_spans
{
self.suggest_cloning(err, ty, expr, None);
self.suggest_cloning(err, ty, expr, None, Some(move_spans));
} else if self.suggest_hoisting_call_outside_loop(err, expr) {
// The place where the the type moves would be misleading to suggest clone.
// #121466
self.suggest_cloning(err, ty, expr, None);
self.suggest_cloning(err, ty, expr, None, Some(move_spans));
}
}
if let Some(pat) = finder.pat {
@ -1085,6 +1085,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
ty: Ty<'tcx>,
mut expr: &'cx hir::Expr<'cx>,
mut other_expr: Option<&'cx hir::Expr<'cx>>,
use_spans: Option<UseSpans<'tcx>>,
) {
if let hir::ExprKind::Struct(_, _, Some(_)) = expr.kind {
// We have `S { foo: val, ..base }`. In `check_aggregate_rvalue` we have a single
@ -1197,8 +1198,44 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
.all(|field| self.implements_clone(field.ty(self.infcx.tcx, args)))
})
{
let ty_span = self.infcx.tcx.def_span(def.did());
let mut span: MultiSpan = ty_span.into();
span.push_span_label(ty_span, "consider implementing `Clone` for this type");
span.push_span_label(expr.span, "you could clone this value");
err.span_note(
self.infcx.tcx.def_span(def.did()),
span,
format!("if `{ty}` implemented `Clone`, you could clone the value"),
);
} else if let ty::Param(param) = ty.kind()
&& let Some(_clone_trait_def) = self.infcx.tcx.lang_items().clone_trait()
&& let generics = self.infcx.tcx.generics_of(self.mir_def_id())
&& let generic_param = generics.type_param(*param, self.infcx.tcx)
&& let param_span = self.infcx.tcx.def_span(generic_param.def_id)
&& if let Some(UseSpans::FnSelfUse { kind, .. }) = use_spans
&& let CallKind::FnCall { fn_trait_id, self_ty } = kind
&& let ty::Param(_) = self_ty.kind()
&& ty == self_ty
&& [
self.infcx.tcx.lang_items().fn_once_trait(),
self.infcx.tcx.lang_items().fn_mut_trait(),
self.infcx.tcx.lang_items().fn_trait(),
]
.contains(&Some(fn_trait_id))
{
// Do not suggest `F: FnOnce() + Clone`.
false
} else {
true
}
{
let mut span: MultiSpan = param_span.into();
span.push_span_label(
param_span,
"consider constraining this type parameter with `Clone`",
);
span.push_span_label(expr.span, "you could clone this value");
err.span_help(
span,
format!("if `{ty}` implemented `Clone`, you could clone the value"),
);
}
@ -1403,7 +1440,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
if let Some(expr) = self.find_expr(borrow_span)
&& let Some(ty) = typeck_results.node_type_opt(expr.hir_id)
{
self.suggest_cloning(&mut err, ty, expr, self.find_expr(span));
self.suggest_cloning(&mut err, ty, expr, self.find_expr(span), Some(move_spans));
}
self.buffer_error(err);
}