If the moved value is a mut reference, it is used in a generic function and it's type is a generic param, it can be reborrowed to avoid moving.

for example:

```rust
struct Y(u32);
// x's type is '& mut Y' and it is used in `fn generic<T>(x: T) {}`.
fn generic<T>(x: T) {}
```

fixes #127285
This commit is contained in:
surechen 2024-07-10 20:27:38 +08:00
parent 7d356ebde3
commit 4821b84b92
7 changed files with 128 additions and 41 deletions

View File

@ -205,9 +205,17 @@ pub(crate) fn report_use_of_moved_or_uninitialized(
is_loop_move = true;
}
let mut has_suggest_reborrow = false;
if !seen_spans.contains(&move_span) {
if !closure {
self.suggest_ref_or_clone(mpi, &mut err, &mut in_pattern, move_spans);
self.suggest_ref_or_clone(
mpi,
&mut err,
&mut in_pattern,
move_spans,
moved_place.as_ref(),
&mut has_suggest_reborrow,
);
}
let msg_opt = CapturedMessageOpt {
@ -215,6 +223,7 @@ pub(crate) fn report_use_of_moved_or_uninitialized(
is_loop_message,
is_move_msg,
is_loop_move,
has_suggest_reborrow,
maybe_reinitialized_locations_is_empty: maybe_reinitialized_locations
.is_empty(),
};
@ -259,17 +268,7 @@ pub(crate) fn report_use_of_moved_or_uninitialized(
if is_loop_move & !in_pattern && !matches!(use_spans, UseSpans::ClosureUse { .. }) {
if let ty::Ref(_, _, hir::Mutability::Mut) = ty.kind() {
// We have a `&mut` ref, we need to reborrow on each iteration (#62112).
err.span_suggestion_verbose(
span.shrink_to_lo(),
format!(
"consider creating a fresh reborrow of {} here",
self.describe_place(moved_place)
.map(|n| format!("`{n}`"))
.unwrap_or_else(|| "the mutable reference".to_string()),
),
"&mut *",
Applicability::MachineApplicable,
);
self.suggest_reborrow(&mut err, span, moved_place);
}
}
@ -346,6 +345,8 @@ fn suggest_ref_or_clone(
err: &mut Diag<'infcx>,
in_pattern: &mut bool,
move_spans: UseSpans<'tcx>,
moved_place: PlaceRef<'tcx>,
has_suggest_reborrow: &mut bool,
) {
let move_span = match move_spans {
UseSpans::ClosureUse { capture_kind_span, .. } => capture_kind_span,
@ -435,20 +436,44 @@ fn visit_pat(&mut self, p: &'hir hir::Pat<'hir>) {
let parent = self.infcx.tcx.parent_hir_node(expr.hir_id);
let (def_id, args, offset) = if let hir::Node::Expr(parent_expr) = parent
&& let hir::ExprKind::MethodCall(_, _, args, _) = parent_expr.kind
&& let Some(def_id) = typeck.type_dependent_def_id(parent_expr.hir_id)
{
(def_id.as_local(), args, 1)
(typeck.type_dependent_def_id(parent_expr.hir_id), args, 1)
} else if let hir::Node::Expr(parent_expr) = parent
&& let hir::ExprKind::Call(call, args) = parent_expr.kind
&& let ty::FnDef(def_id, _) = typeck.node_type(call.hir_id).kind()
{
(def_id.as_local(), args, 0)
(Some(*def_id), args, 0)
} else {
(None, &[][..], 0)
};
// If the moved value is a mut reference, it is used in a
// generic function and it's type is a generic param, it can be
// reborrowed to avoid moving.
// for example:
// struct Y(u32);
// x's type is '& mut Y' and it is used in `fn generic<T>(x: T) {}`.
if let Some(def_id) = def_id
&& self.infcx.tcx.def_kind(def_id).is_fn_like()
&& let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
&& let ty::Param(_) =
self.infcx.tcx.fn_sig(def_id).skip_binder().skip_binder().inputs()
[pos + offset]
.kind()
{
let place = &self.move_data.move_paths[mpi].place;
let ty = place.ty(self.body, self.infcx.tcx).ty;
if let ty::Ref(_, _, hir::Mutability::Mut) = ty.kind() {
*has_suggest_reborrow = true;
self.suggest_reborrow(err, expr.span, moved_place);
return;
}
}
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(local_def_id) = def_id.as_local()
&& let node = self.infcx.tcx.hir_node_by_def_id(local_def_id)
&& let Some(fn_sig) = node.fn_sig()
&& let Some(ident) = node.ident()
&& let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
@ -622,6 +647,25 @@ fn visit_expr(&mut self, e: &hir::Expr<'_>) {
}
}
pub fn suggest_reborrow(
&self,
err: &mut Diag<'infcx>,
span: Span,
moved_place: PlaceRef<'tcx>,
) {
err.span_suggestion_verbose(
span.shrink_to_lo(),
format!(
"consider creating a fresh reborrow of {} here",
self.describe_place(moved_place)
.map(|n| format!("`{n}`"))
.unwrap_or_else(|| "the mutable reference".to_string()),
),
"&mut *",
Applicability::MachineApplicable,
);
}
fn report_use_of_uninitialized(
&self,
mpi: MovePathIndex,

View File

@ -768,10 +768,11 @@ struct CapturedMessageOpt {
is_loop_message: bool,
is_move_msg: bool,
is_loop_move: bool,
has_suggest_reborrow: bool,
maybe_reinitialized_locations_is_empty: bool,
}
impl<'tcx> MirBorrowckCtxt<'_, '_, '_, 'tcx> {
impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
/// Finds the spans associated to a move or copy of move_place at location.
pub(super) fn move_spans(
&self,
@ -997,7 +998,7 @@ pub(super) fn retrieve_borrow_spans(&self, borrow: &BorrowData<'_>) -> UseSpans<
#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
fn explain_captures(
&mut self,
err: &mut Diag<'_>,
err: &mut Diag<'infcx>,
span: Span,
move_span: Span,
move_spans: UseSpans<'tcx>,
@ -1009,6 +1010,7 @@ fn explain_captures(
is_loop_message,
is_move_msg,
is_loop_move,
has_suggest_reborrow,
maybe_reinitialized_locations_is_empty,
} = msg_opt;
if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
@ -1182,18 +1184,15 @@ fn explain_captures(
if let ty::Ref(_, _, hir::Mutability::Mut) =
moved_place.ty(self.body, self.infcx.tcx).ty.kind()
{
// If we are in a loop this will be suggested later.
if !is_loop_move {
err.span_suggestion_verbose(
// Suggest `reborrow` in other place for following situations:
// 1. If we are in a loop this will be suggested later.
// 2. If the moved value is a mut reference, it is used in a
// generic function and the corresponding arg's type is generic param.
if !is_loop_move && !has_suggest_reborrow {
self.suggest_reborrow(
err,
move_span.shrink_to_lo(),
format!(
"consider creating a fresh reborrow of {} here",
self.describe_place(moved_place.as_ref())
.map(|n| format!("`{n}`"))
.unwrap_or_else(|| "the mutable reference".to_string()),
),
"&mut *",
Applicability::MachineApplicable,
moved_place.as_ref(),
);
}
}

View File

@ -554,6 +554,7 @@ fn report_cannot_move_from_borrowed_content(
is_loop_message: false,
is_move_msg: false,
is_loop_move: false,
has_suggest_reborrow: false,
maybe_reinitialized_locations_is_empty: true,
};
if let Some(use_spans) = use_spans {

View File

@ -0,0 +1,17 @@
//@ run-rustfix
#![allow(dead_code)]
struct X(u32);
impl X {
fn f(&mut self) {
generic(&mut *self);
self.0 += 1;
//~^ ERROR: use of moved value: `self` [E0382]
}
}
fn generic<T>(_x: T) {}
fn main() {}

View File

@ -0,0 +1,17 @@
//@ run-rustfix
#![allow(dead_code)]
struct X(u32);
impl X {
fn f(&mut self) {
generic(self);
self.0 += 1;
//~^ ERROR: use of moved value: `self` [E0382]
}
}
fn generic<T>(_x: T) {}
fn main() {}

View File

@ -0,0 +1,18 @@
error[E0382]: use of moved value: `self`
--> $DIR/moved-value-suggest-reborrow-issue-127285.rs:10:9
|
LL | fn f(&mut self) {
| --------- move occurs because `self` has type `&mut X`, which does not implement the `Copy` trait
LL | generic(self);
| ---- value moved here
LL | self.0 += 1;
| ^^^^^^^^^^^ value used here after move
|
help: consider creating a fresh reborrow of `self` here
|
LL | generic(&mut *self);
| ++++++
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0382`.

View File

@ -8,19 +8,10 @@ LL | for _ in 0..3 {
LL | Other::handle(value);
| ^^^^^ value moved here, in previous iteration of loop
|
note: consider changing this parameter type in function `handle` to borrow instead if owning the value isn't necessary
--> $DIR/mut-borrow-in-loop-2.rs:8:22
|
LL | fn handle(value: T) -> Self;
| ------ ^ this parameter takes ownership of the value
| |
| in this function
help: consider moving the expression out of the loop so it is only moved once
|
LL ~ let mut value = Other::handle(value);
LL ~ for _ in 0..3 {
LL ~ value;
help: consider creating a fresh reborrow of `value` here
|
LL | Other::handle(&mut *value);
| ++++++
help: consider creating a fresh reborrow of `value` here
|
LL | Other::handle(&mut *value);