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Rollup merge of #124599 - estebank:issue-41708, r=wesleywiser

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Suggest borrowing on fn argument that is `impl AsRef`

When encountering a move conflict, on an expression that is `!Copy` passed as an argument to an `fn` that is `impl AsRef`, suggest borrowing the expression.

```
error[E0382]: use of moved value: `bar`
  --> f204.rs:14:15
   |
12 |     let bar = Bar;
   |         --- move occurs because `bar` has type `Bar`, which does not implement the `Copy` trait
13 |     foo(bar);
   |         --- value moved here
14 |     let baa = bar;
   |               ^^^ value used here after move
   |
help: borrow the value to avoid moving it
   |
13 |     foo(&bar);
   |         +
```

Fix #41708
This commit is contained in:
Matthias Krüger 2024-07-11 17:01:36 +02:00 • committed by GitHub
commit 8de487fdbd
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5 changed files with 224 additions and 19 deletions
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89
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
View file

@ -445,6 +445,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
} else {
(None, &[][..], 0)
};
let mut can_suggest_clone = true;
if let Some(def_id) = def_id
&& let node = self.infcx.tcx.hir_node_by_def_id(def_id)
&& let Some(fn_sig) = node.fn_sig()
@ -452,24 +453,73 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
&& let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
&& let Some(arg) = fn_sig.decl.inputs.get(pos + offset)
{
let mut span: MultiSpan = arg.span.into();
span.push_span_label(
arg.span,
"this parameter takes ownership of the value".to_string(),
);
let descr = match node.fn_kind() {
Some(hir::intravisit::FnKind::ItemFn(..)) | None => "function",
Some(hir::intravisit::FnKind::Method(..)) => "method",
Some(hir::intravisit::FnKind::Closure) => "closure",
};
span.push_span_label(ident.span, format!("in this {descr}"));
err.span_note(
span,
format!(
"consider changing this parameter type in {descr} `{ident}` to borrow \
instead if owning the value isn't necessary",
),
);
let mut is_mut = false;
if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = arg.kind
&& let Res::Def(DefKind::TyParam, param_def_id) = path.res
&& self
.infcx
.tcx
.predicates_of(def_id)
.instantiate_identity(self.infcx.tcx)
.predicates
.into_iter()
.any(|pred| {
if let ty::ClauseKind::Trait(predicate) = pred.kind().skip_binder()
&& [
self.infcx.tcx.get_diagnostic_item(sym::AsRef),
self.infcx.tcx.get_diagnostic_item(sym::AsMut),
self.infcx.tcx.get_diagnostic_item(sym::Borrow),
self.infcx.tcx.get_diagnostic_item(sym::BorrowMut),
]
.contains(&Some(predicate.def_id()))
&& let ty::Param(param) = predicate.self_ty().kind()
&& let generics = self.infcx.tcx.generics_of(def_id)
&& let param = generics.type_param(*param, self.infcx.tcx)
&& param.def_id == param_def_id
{
if [
self.infcx.tcx.get_diagnostic_item(sym::AsMut),
self.infcx.tcx.get_diagnostic_item(sym::BorrowMut),
]
.contains(&Some(predicate.def_id()))
{
is_mut = true;
}
true
} else {
false
}
})
{
// The type of the argument corresponding to the expression that got moved
// is a type parameter `T`, which is has a `T: AsRef` obligation.
err.span_suggestion_verbose(
expr.span.shrink_to_lo(),
"borrow the value to avoid moving it",
format!("&{}", if is_mut { "mut " } else { "" }),
Applicability::MachineApplicable,
);
can_suggest_clone = is_mut;
} else {
let mut span: MultiSpan = arg.span.into();
span.push_span_label(
arg.span,
"this parameter takes ownership of the value".to_string(),
);
let descr = match node.fn_kind() {
Some(hir::intravisit::FnKind::ItemFn(..)) | None => "function",
Some(hir::intravisit::FnKind::Method(..)) => "method",
Some(hir::intravisit::FnKind::Closure) => "closure",
};
span.push_span_label(ident.span, format!("in this {descr}"));
err.span_note(
span,
format!(
"consider changing this parameter type in {descr} `{ident}` to \
borrow instead if owning the value isn't necessary",
),
);
}
}
let place = &self.move_data.move_paths[mpi].place;
let ty = place.ty(self.body, self.infcx.tcx).ty;
@ -487,9 +537,10 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
ClosureKind::Coroutine(CoroutineKind::Desugared(_, CoroutineSource::Block)),
..
} = move_spans
&& can_suggest_clone
{
self.suggest_cloning(err, ty, expr, None, Some(move_spans));
} else if self.suggest_hoisting_call_outside_loop(err, expr) {
} else if self.suggest_hoisting_call_outside_loop(err, expr) && can_suggest_clone {
// The place where the type moves would be misleading to suggest clone.
// #121466
self.suggest_cloning(err, ty, expr, None, Some(move_spans));