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Peel off explicit (or implicit) deref before suggesting clone on move error in borrowck, remove some hacks #128244

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Aug 1, 2024
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Peel off explicit (or implicit) deref before suggesting clone on move error in borrowck, remove some hacks #128244

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92 changes: 24 additions & 68 deletions compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -570,11 +570,11 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
} = move_spans
&& can_suggest_clone
{
self.suggest_cloning(err, ty, expr, None, Some(move_spans));
self.suggest_cloning(err, ty, expr, Some(move_spans));
} 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));
self.suggest_cloning(err, ty, expr, Some(move_spans));
}
}

Expand Down Expand Up @@ -1236,8 +1236,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
&self,
err: &mut Diag<'_>,
ty: Ty<'tcx>,
mut expr: &'tcx hir::Expr<'tcx>,
mut other_expr: Option<&'tcx hir::Expr<'tcx>>,
expr: &'tcx hir::Expr<'tcx>,
use_spans: Option<UseSpans<'tcx>>,
) {
if let hir::ExprKind::Struct(_, _, Some(_)) = expr.kind {
Expand All @@ -1249,66 +1248,6 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
return;
}

if let Some(some_other_expr) = other_expr
&& let Some(parent_binop) =
self.infcx.tcx.hir().parent_iter(expr.hir_id).find_map(|n| {
if let (hir_id, hir::Node::Expr(e)) = n
&& let hir::ExprKind::AssignOp(_binop, target, _arg) = e.kind
&& target.hir_id == expr.hir_id
{
Some(hir_id)
} else {
None
}
})
&& let Some(other_parent_binop) =
self.infcx.tcx.hir().parent_iter(some_other_expr.hir_id).find_map(|n| {
if let (hir_id, hir::Node::Expr(expr)) = n
&& let hir::ExprKind::AssignOp(..) = expr.kind
{
Some(hir_id)
} else {
None
}
})
&& parent_binop == other_parent_binop
{
// Explicitly look for `expr += other_expr;` and avoid suggesting
// `expr.clone() += other_expr;`, instead suggesting `expr += other_expr.clone();`.
other_expr = Some(expr);
expr = some_other_expr;
}
'outer: {
if let ty::Ref(..) = ty.kind() {
// We check for either `let binding = foo(expr, other_expr);` or
// `foo(expr, other_expr);` and if so we don't suggest an incorrect
// `foo(expr, other_expr).clone()`
if let Some(other_expr) = other_expr
&& let Some(parent_let) =
self.infcx.tcx.hir().parent_iter(expr.hir_id).find_map(|n| {
if let (hir_id, hir::Node::LetStmt(_) | hir::Node::Stmt(_)) = n {
Some(hir_id)
} else {
None
}
})
&& let Some(other_parent_let) =
self.infcx.tcx.hir().parent_iter(other_expr.hir_id).find_map(|n| {
if let (hir_id, hir::Node::LetStmt(_) | hir::Node::Stmt(_)) = n {
Some(hir_id)
} else {
None
}
})
&& parent_let == other_parent_let
{
// Explicitly check that we don't have `foo(&*expr, other_expr)`, as cloning the
// result of `foo(...)` won't help.
break 'outer;
}
}
}
let ty = ty.peel_refs();
if self.implements_clone(ty) {
self.suggest_cloning_inner(err, ty, expr);
} else if let ty::Adt(def, args) = ty.kind()
Expand Down Expand Up @@ -1575,10 +1514,27 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
);
self.suggest_copy_for_type_in_cloned_ref(&mut err, place);
let typeck_results = self.infcx.tcx.typeck(self.mir_def_id());
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), Some(move_spans));
if let Some(expr) = self.find_expr(borrow_span) {
// This is a borrow span, so we want to suggest cloning the referent.
if let hir::ExprKind::AddrOf(_, _, borrowed_expr) = expr.kind
&& let Some(ty) = typeck_results.expr_ty_opt(borrowed_expr)
{
self.suggest_cloning(&mut err, ty, borrowed_expr, Some(move_spans));
} else if typeck_results.expr_adjustments(expr).first().is_some_and(|adj| {
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Implicit borrow, like in f() when f: impl FnMut.

matches!(
adj.kind,
ty::adjustment::Adjust::Borrow(ty::adjustment::AutoBorrow::Ref(
_,
ty::adjustment::AutoBorrowMutability::Not
| ty::adjustment::AutoBorrowMutability::Mut {
allow_two_phase_borrow: ty::adjustment::AllowTwoPhase::No
}
))
)
}) && let Some(ty) = typeck_results.expr_ty_opt(expr)
{
self.suggest_cloning(&mut err, ty, expr, Some(move_spans));
}
}
self.buffer_error(err);
}
Expand Down
16 changes: 4 additions & 12 deletions compiler/rustc_borrowck/src/diagnostics/move_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -565,9 +565,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {

fn add_move_hints(&self, error: GroupedMoveError<'tcx>, err: &mut Diag<'_>, span: Span) {
match error {
GroupedMoveError::MovesFromPlace {
mut binds_to, move_from, span: other_span, ..
} => {
GroupedMoveError::MovesFromPlace { mut binds_to, move_from, .. } => {
self.add_borrow_suggestions(err, span);
if binds_to.is_empty() {
let place_ty = move_from.ty(self.body, self.infcx.tcx).ty;
Expand All @@ -577,7 +575,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
};

if let Some(expr) = self.find_expr(span) {
self.suggest_cloning(err, place_ty, expr, self.find_expr(other_span), None);
self.suggest_cloning(err, place_ty, expr, None);
}

err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
Expand Down Expand Up @@ -609,13 +607,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
};

if let Some(expr) = self.find_expr(use_span) {
self.suggest_cloning(
err,
place_ty,
expr,
self.find_expr(span),
Some(use_spans),
);
self.suggest_cloning(err, place_ty, expr, Some(use_spans));
}

err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
Expand Down Expand Up @@ -740,7 +732,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
let place_desc = &format!("`{}`", self.local_names[*local].unwrap());

if let Some(expr) = self.find_expr(binding_span) {
self.suggest_cloning(err, bind_to.ty, expr, None, None);
self.suggest_cloning(err, bind_to.ty, expr, None);
}

err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/associated-types/associated-types-outlives.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ LL | pub fn free_and_use<T: for<'a> Foo<'a>,
| ^ consider constraining this type parameter with `Clone`
...
LL | 's: loop { y = denormalise(&x); break }
| -- you could clone this value
| - you could clone this value

error: aborting due to 1 previous error

Expand Down
1 change: 0 additions & 1 deletion tests/ui/augmented-assignments.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,6 @@ fn main() {
x;
//~^ ERROR cannot move out of `x` because it is borrowed
//~| move out of `x` occurs here
//~| HELP consider cloning

let y = Int(2);
//~^ HELP consider changing this to be mutable
Expand Down
7 changes: 1 addition & 6 deletions tests/ui/augmented-assignments.stderr
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Expand Up @@ -8,14 +8,9 @@ LL | x
...
LL | x;
| ^ move out of `x` occurs here
|
help: consider cloning the value if the performance cost is acceptable
|
LL | x.clone();
| ++++++++

error[E0596]: cannot borrow `y` as mutable, as it is not declared as mutable
--> $DIR/augmented-assignments.rs:25:5
--> $DIR/augmented-assignments.rs:24:5
|
LL | y
| ^ cannot borrow as mutable
Expand Down
4 changes: 2 additions & 2 deletions tests/ui/binop/binop-move-semantics.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,7 @@ help: if `T` implemented `Clone`, you could clone the value
LL | fn move_borrowed<T: Add<Output=()>>(x: T, mut y: T) {
| ^ consider constraining this type parameter with `Clone`
LL | let m = &x;
| -- you could clone this value
| - you could clone this value

error[E0505]: cannot move out of `y` because it is borrowed
--> $DIR/binop-move-semantics.rs:23:5
Expand All @@ -88,7 +88,7 @@ LL | fn move_borrowed<T: Add<Output=()>>(x: T, mut y: T) {
| ^ consider constraining this type parameter with `Clone`
LL | let m = &x;
LL | let n = &mut y;
| ------ you could clone this value
| - you could clone this value

error[E0507]: cannot move out of `*m` which is behind a mutable reference
--> $DIR/binop-move-semantics.rs:30:5
Expand Down
10 changes: 4 additions & 6 deletions tests/ui/borrowck/borrow-tuple-fields.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -13,9 +13,8 @@ LL | r.use_ref();
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let r = &x.0;
LL + let r = x.0.clone();
|
LL | let r = &x.0.clone();
| ++++++++

error[E0502]: cannot borrow `x.0` as mutable because it is also borrowed as immutable
--> $DIR/borrow-tuple-fields.rs:18:13
Expand Down Expand Up @@ -51,9 +50,8 @@ LL | r.use_ref();
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let r = &x.0;
LL + let r = x.0.clone();
|
LL | let r = &x.0.clone();
| ++++++++

error[E0502]: cannot borrow `x.0` as mutable because it is also borrowed as immutable
--> $DIR/borrow-tuple-fields.rs:33:13
Expand Down
4 changes: 2 additions & 2 deletions tests/ui/borrowck/borrowck-bad-nested-calls-move.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ LL | a);
help: consider cloning the value if the performance cost is acceptable
|
LL - &*a,
LL + a.clone(),
LL + &a.clone(),
|

error[E0505]: cannot move out of `a` because it is borrowed
Expand All @@ -32,7 +32,7 @@ LL | a);
help: consider cloning the value if the performance cost is acceptable
|
LL - &*a,
LL + a.clone(),
LL + &a.clone(),
|

error: aborting due to 2 previous errors
Expand Down
10 changes: 4 additions & 6 deletions tests/ui/borrowck/borrowck-field-sensitivity.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -52,9 +52,8 @@ LL | drop(**p);
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let p = &x.b;
LL + let p = x.b.clone();
|
LL | let p = &x.b.clone();
| ++++++++

error[E0505]: cannot move out of `x.b` because it is borrowed
--> $DIR/borrowck-field-sensitivity.rs:41:14
Expand All @@ -70,9 +69,8 @@ LL | drop(**p);
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let p = &x.b;
LL + let p = x.b.clone();
|
LL | let p = &x.b.clone();
| ++++++++

error[E0499]: cannot borrow `x.a` as mutable more than once at a time
--> $DIR/borrowck-field-sensitivity.rs:48:13
Expand Down
5 changes: 0 additions & 5 deletions tests/ui/borrowck/borrowck-issue-48962.stderr
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Expand Up @@ -17,11 +17,6 @@ LL | {src};
| --- value moved here
LL | src.0 = 66;
| ^^^^^^^^^^ value used here after move
|
help: consider cloning the value if the performance cost is acceptable
|
LL | {src.clone()};
| ++++++++

error: aborting due to 2 previous errors

Expand Down
10 changes: 4 additions & 6 deletions tests/ui/borrowck/borrowck-loan-blocks-move-cc.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -16,9 +16,8 @@ LL | w.use_ref();
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let w = &v;
LL + let w = v.clone();
|
LL | let w = &v.clone();
| ++++++++

error[E0505]: cannot move out of `v` because it is borrowed
--> $DIR/borrowck-loan-blocks-move-cc.rs:24:19
Expand All @@ -38,9 +37,8 @@ LL | w.use_ref();
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let w = &v;
LL + let w = v.clone();
|
LL | let w = &v.clone();
| ++++++++

error: aborting due to 2 previous errors

Expand Down
5 changes: 2 additions & 3 deletions tests/ui/borrowck/borrowck-loan-blocks-move.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -12,9 +12,8 @@ LL | w.use_ref();
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let w = &v;
LL + let w = v.clone();
|
LL | let w = &v.clone();
| ++++++++

error: aborting due to 1 previous error

Expand Down
5 changes: 2 additions & 3 deletions tests/ui/borrowck/borrowck-move-from-subpath-of-borrowed-path.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -13,9 +13,8 @@ LL | b.use_ref();
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let b = &a;
LL + let b = a.clone();
|
LL | let b = &a.clone();
| ++++++++

error: aborting due to 1 previous error

Expand Down
2 changes: 1 addition & 1 deletion tests/ui/borrowck/borrowck-move-mut-base-ptr.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ LL | p.use_ref();
help: consider cloning the value if the performance cost is acceptable
|
LL - let p: &isize = &*t0; // Freezes `*t0`
LL + let p: &isize = t0.clone(); // Freezes `*t0`
LL + let p: &isize = &t0.clone(); // Freezes `*t0`
|

error: aborting due to 1 previous error
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/borrowck/borrowck-move-subcomponent.stderr
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Expand Up @@ -17,7 +17,7 @@ LL | struct S {
| ^^^^^^^^ consider implementing `Clone` for this type
...
LL | let pb = &a;
| -- you could clone this value
| - you could clone this value

error: aborting due to 1 previous error

Expand Down
15 changes: 6 additions & 9 deletions tests/ui/borrowck/borrowck-multiple-captures.stderr
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Expand Up @@ -17,9 +17,8 @@ LL | borrow(&*p1);
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let p1 = &x1;
LL + let p1 = x1.clone();
|
LL | let p1 = &x1.clone();
| ++++++++

error[E0505]: cannot move out of `x2` because it is borrowed
--> $DIR/borrowck-multiple-captures.rs:12:19
Expand All @@ -39,9 +38,8 @@ LL | borrow(&*p2);
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let p2 = &x2;
LL + let p2 = x2.clone();
|
LL | let p2 = &x2.clone();
| ++++++++

error[E0382]: use of moved value: `x1`
--> $DIR/borrowck-multiple-captures.rs:27:19
Expand Down Expand Up @@ -108,9 +106,8 @@ LL | borrow(&*p);
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let p = &x;
LL + let p = x.clone();
|
LL | let p = &x.clone();
| ++++++++

error[E0382]: use of moved value: `x`
--> $DIR/borrowck-multiple-captures.rs:52:14
Expand Down
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