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merged 5 commits into from
Jul 25, 2025
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Tweak output for non-Clone values moved into closures #144200

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690ae52
Tweak borrowck label pointing at `!Copy` value moved into closure
estebank Jul 20, 2025
5082e6a
Generalize logic pointing at binding moved into closure
estebank Jul 20, 2025
8df93e6
Tweak spans when encountering multiline initializer in move error
estebank Jul 20, 2025
dafc9f9
Reduce comment verbosity
estebank Jul 21, 2025
6237e73
Point at the type that doesn't impl `Clone` in more cases beyond clos…
estebank Jul 21, 2025
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134 changes: 83 additions & 51 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 @@ -115,10 +115,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
fn append_to_grouped_errors(
&self,
grouped_errors: &mut Vec<GroupedMoveError<'tcx>>,
error: MoveError<'tcx>,
MoveError { place: original_path, location, kind }: MoveError<'tcx>,
) {
let MoveError { place: original_path, location, kind } = error;

// Note: that the only time we assign a place isn't a temporary
// to a user variable is when initializing it.
// If that ever stops being the case, then the ever initialized
Expand Down Expand Up @@ -251,54 +249,47 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
}

fn report(&mut self, error: GroupedMoveError<'tcx>) {
let (mut err, err_span) = {
let (span, use_spans, original_path, kind) = match error {
GroupedMoveError::MovesFromPlace { span, original_path, ref kind, .. }
| GroupedMoveError::MovesFromValue { span, original_path, ref kind, .. } => {
(span, None, original_path, kind)
}
GroupedMoveError::OtherIllegalMove { use_spans, original_path, ref kind } => {
(use_spans.args_or_use(), Some(use_spans), original_path, kind)
}
};
debug!(
"report: original_path={:?} span={:?}, kind={:?} \
original_path.is_upvar_field_projection={:?}",
original_path,
span,
kind,
self.is_upvar_field_projection(original_path.as_ref())
);
if self.has_ambiguous_copy(original_path.ty(self.body, self.infcx.tcx).ty) {
// If the type may implement Copy, skip the error.
// It's an error with the Copy implementation (e.g. duplicate Copy) rather than borrow check
self.dcx().span_delayed_bug(
let (span, use_spans, original_path, kind) = match error {
GroupedMoveError::MovesFromPlace { span, original_path, ref kind, .. }
| GroupedMoveError::MovesFromValue { span, original_path, ref kind, .. } => {
(span, None, original_path, kind)
}
GroupedMoveError::OtherIllegalMove { use_spans, original_path, ref kind } => {
(use_spans.args_or_use(), Some(use_spans), original_path, kind)
}
};
debug!(
"report: original_path={:?} span={:?}, kind={:?} \
original_path.is_upvar_field_projection={:?}",
original_path,
span,
kind,
self.is_upvar_field_projection(original_path.as_ref())
);
if self.has_ambiguous_copy(original_path.ty(self.body, self.infcx.tcx).ty) {
// If the type may implement Copy, skip the error.
// It's an error with the Copy implementation (e.g. duplicate Copy) rather than borrow check
self.dcx()
.span_delayed_bug(span, "Type may implement copy, but there is no other error.");
return;
}
let mut err = match kind {
&IllegalMoveOriginKind::BorrowedContent { target_place } => self
.report_cannot_move_from_borrowed_content(
original_path,
target_place,
span,
"Type may implement copy, but there is no other error.",
);
return;
use_spans,
),
&IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
self.cannot_move_out_of_interior_of_drop(span, ty)
}
&IllegalMoveOriginKind::InteriorOfSliceOrArray { ty, is_index } => {
self.cannot_move_out_of_interior_noncopy(span, ty, Some(is_index))
}
(
match kind {
&IllegalMoveOriginKind::BorrowedContent { target_place } => self
.report_cannot_move_from_borrowed_content(
original_path,
target_place,
span,
use_spans,
),
&IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
self.cannot_move_out_of_interior_of_drop(span, ty)
}
&IllegalMoveOriginKind::InteriorOfSliceOrArray { ty, is_index } => {
self.cannot_move_out_of_interior_noncopy(span, ty, Some(is_index))
}
},
span,
)
};

self.add_move_hints(error, &mut err, err_span);
self.add_move_hints(error, &mut err, span);
self.buffer_error(err);
}

Expand Down Expand Up @@ -482,7 +473,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
self.cannot_move_out_of_interior_noncopy(span, ty, None)
}
ty::Closure(def_id, closure_args)
if def_id.as_local() == Some(self.mir_def_id()) && upvar_field.is_some() =>
if def_id.as_local() == Some(self.mir_def_id())
&& let Some(upvar_field) = upvar_field =>
{
let closure_kind_ty = closure_args.as_closure().kind_ty();
let closure_kind = match closure_kind_ty.to_opt_closure_kind() {
Expand All @@ -495,7 +487,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
let capture_description =
format!("captured variable in an `{closure_kind}` closure");

let upvar = &self.upvars[upvar_field.unwrap().index()];
let upvar = &self.upvars[upvar_field.index()];
let upvar_hir_id = upvar.get_root_variable();
let upvar_name = upvar.to_string(tcx);
let upvar_span = tcx.hir_span(upvar_hir_id);
Expand Down Expand Up @@ -605,7 +597,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
}
// No binding. Nothing to suggest.
GroupedMoveError::OtherIllegalMove { ref original_path, use_spans, .. } => {
let use_span = use_spans.var_or_use();
let mut use_span = use_spans.var_or_use();
let place_ty = original_path.ty(self.body, self.infcx.tcx).ty;
let place_desc = match self.describe_place(original_path.as_ref()) {
Some(desc) => format!("`{desc}`"),
Expand All @@ -622,19 +614,59 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
);
}

if let Some(upvar_field) = self
.prefixes(original_path.as_ref(), PrefixSet::All)
.find_map(|p| self.is_upvar_field_projection(p))
{
// Look for the introduction of the original binding being moved.
let upvar = &self.upvars[upvar_field.index()];
let upvar_hir_id = upvar.get_root_variable();
use_span = match self.infcx.tcx.parent_hir_node(upvar_hir_id) {
hir::Node::Param(param) => {
// Instead of pointing at the path where we access the value within a
// closure, we point at the type of the outer `fn` argument.
param.ty_span
}
hir::Node::LetStmt(stmt) => match (stmt.ty, stmt.init) {
// We point at the type of the outer let-binding.
(Some(ty), _) => ty.span,
// We point at the initializer of the outer let-binding, but only if it
// isn't something that spans multiple lines, like a closure, as the
// ASCII art gets messy.
(None, Some(init))
if !self.infcx.tcx.sess.source_map().is_multiline(init.span) =>
{
init.span
}
_ => use_span,
},
_ => use_span,
};
}

err.subdiagnostic(crate::session_diagnostics::TypeNoCopy::Label {
is_partial_move: false,
ty: place_ty,
place: &place_desc,
span: use_span,
});

let mut pointed_at_span = false;
use_spans.args_subdiag(err, |args_span| {
if args_span == span || args_span == use_span {
pointed_at_span = true;
}
crate::session_diagnostics::CaptureArgLabel::MoveOutPlace {
place: place_desc,
place: place_desc.clone(),
args_span,
}
});
if !pointed_at_span && use_span != span {
err.subdiagnostic(crate::session_diagnostics::CaptureArgLabel::MoveOutPlace {
place: place_desc,
args_span: span,
});
}

self.add_note_for_packed_struct_derive(err, original_path.local);
}
Expand Down
7 changes: 3 additions & 4 deletions tests/ui/async-await/async-closures/closure-shim-borrowck-error.stderr
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Original file line number Diff line number Diff line change
@@ -1,14 +1,13 @@
error[E0507]: cannot move out of `x` which is behind a mutable reference
--> $DIR/closure-shim-borrowck-error.rs:11:18
|
LL | fn hello(x: Ty) {
| -- move occurs because `x` has type `Ty`, which does not implement the `Copy` trait
LL | needs_fn_mut(async || {
| ^^^^^^^^ `x` is moved here
LL |
LL | x.hello();
| -
| |
| variable moved due to use in coroutine
| move occurs because `x` has type `Ty`, which does not implement the `Copy` trait
| - variable moved due to use in coroutine
|
note: if `Ty` implemented `Clone`, you could clone the value
--> $DIR/closure-shim-borrowck-error.rs:17:1
Expand Down
5 changes: 4 additions & 1 deletion tests/ui/async-await/async-closures/move-out-of-ref.stderr
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Original file line number Diff line number Diff line change
@@ -1,8 +1,11 @@
error[E0507]: cannot move out of `*x` which is behind a shared reference
--> $DIR/move-out-of-ref.rs:9:9
|
LL | fn hello(x: &Ty) {
| --- move occurs because `*x` has type `Ty`, which does not implement the `Copy` trait
LL | let c = async || {
LL | *x;
| ^^ move occurs because `*x` has type `Ty`, which does not implement the `Copy` trait
| ^^ `*x` is moved here
|
note: if `Ty` implemented `Clone`, you could clone the value
--> $DIR/move-out-of-ref.rs:5:1
Expand Down
6 changes: 4 additions & 2 deletions tests/ui/borrowck/borrowck-in-static.stderr
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Expand Up @@ -2,9 +2,11 @@ error[E0507]: cannot move out of `x`, a captured variable in an `Fn` closure
--> $DIR/borrowck-in-static.rs:5:17
|
LL | let x = Box::new(0);
| - captured outer variable
| - ----------- move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
| |
| captured outer variable
LL | Box::new(|| x)
| -- ^ move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
| -- ^ `x` is moved here
| |
| captured by this `Fn` closure
|
Expand Down
10 changes: 5 additions & 5 deletions tests/ui/borrowck/borrowck-move-by-capture.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -2,14 +2,14 @@ error[E0507]: cannot move out of `bar`, a captured variable in an `FnMut` closur
--> $DIR/borrowck-move-by-capture.rs:9:29
|
LL | let bar: Box<_> = Box::new(3);
| --- captured outer variable
| --- ------ move occurs because `bar` has type `Box<isize>`, which does not implement the `Copy` trait
| |
| captured outer variable
LL | let _g = to_fn_mut(|| {
| -- captured by this `FnMut` closure
LL | let _h = to_fn_once(move || -> isize { *bar });
| ^^^^^^^^^^^^^^^^ ----
| | |
| | variable moved due to use in closure
| | move occurs because `bar` has type `Box<isize>`, which does not implement the `Copy` trait
| ^^^^^^^^^^^^^^^^ ---- variable moved due to use in closure
| |
| `bar` is moved here
|
help: consider cloning the value before moving it into the closure
Expand Down
7 changes: 5 additions & 2 deletions tests/ui/borrowck/issue-103624.stderr
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Expand Up @@ -2,13 +2,16 @@ error[E0507]: cannot move out of `self.b`, as `self` is a captured variable in a
--> $DIR/issue-103624.rs:16:13
|
LL | async fn foo(&self) {
| ----- captured outer variable
| -----
| |
| captured outer variable
| move occurs because `self.b` has type `StructB`, which does not implement the `Copy` trait
LL | let bar = self.b.bar().await;
LL | spawn_blocking(move || {
| ------- captured by this `Fn` closure
LL |
LL | self.b;
| ^^^^^^ move occurs because `self.b` has type `StructB`, which does not implement the `Copy` trait
| ^^^^^^ `self.b` is moved here
|
note: if `StructB` implemented `Clone`, you could clone the value
--> $DIR/issue-103624.rs:23:1
Expand Down
6 changes: 4 additions & 2 deletions tests/ui/issues/issue-4335.stderr
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Expand Up @@ -2,9 +2,11 @@ error[E0507]: cannot move out of `*v`, as `v` is a captured variable in an `FnMu
--> $DIR/issue-4335.rs:6:20
|
LL | fn f<'r, T>(v: &'r T) -> Box<dyn FnMut() -> T + 'r> {
| - captured outer variable
| - ----- move occurs because `*v` has type `T`, which does not implement the `Copy` trait
| |
| captured outer variable
LL | id(Box::new(|| *v))
| -- ^^ move occurs because `*v` has type `T`, which does not implement the `Copy` trait
| -- ^^ `*v` is moved here
| |
| captured by this `FnMut` closure
|
Expand Down
6 changes: 4 additions & 2 deletions tests/ui/moves/moves-based-on-type-move-out-of-closure-env-issue-1965.stderr
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Expand Up @@ -2,9 +2,11 @@ error[E0507]: cannot move out of `i`, a captured variable in an `Fn` closure
--> $DIR/moves-based-on-type-move-out-of-closure-env-issue-1965.rs:9:28
|
LL | let i = Box::new(3);
| - captured outer variable
| - ----------- move occurs because `i` has type `Box<usize>`, which does not implement the `Copy` trait
| |
| captured outer variable
LL | let _f = to_fn(|| test(i));
| -- ^ move occurs because `i` has type `Box<usize>`, which does not implement the `Copy` trait
| -- ^ `i` is moved here
| |
| captured by this `Fn` closure
|
Expand Down
6 changes: 4 additions & 2 deletions tests/ui/nll/issue-52663-span-decl-captured-variable.stderr
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Expand Up @@ -2,9 +2,11 @@ error[E0507]: cannot move out of `x.0`, as `x` is a captured variable in an `Fn`
--> $DIR/issue-52663-span-decl-captured-variable.rs:8:26
|
LL | let x = (vec![22], vec![44]);
| - captured outer variable
| - -------------------- move occurs because `x.0` has type `Vec<i32>`, which does not implement the `Copy` trait
| |
| captured outer variable
LL | expect_fn(|| drop(x.0));
| -- ^^^ move occurs because `x.0` has type `Vec<i32>`, which does not implement the `Copy` trait
| -- ^^^ `x.0` is moved here
| |
| captured by this `Fn` closure
|
Expand Down
18 changes: 8 additions & 10 deletions tests/ui/suggestions/option-content-move2.stderr
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Expand Up @@ -2,35 +2,33 @@ error[E0507]: cannot move out of `var`, a captured variable in an `FnMut` closur
--> $DIR/option-content-move2.rs:11:9
|
LL | let mut var = None;
| ------- captured outer variable
| ------- ---- move occurs because `var` has type `Option<NotCopyable>`, which does not implement the `Copy` trait
| |
| captured outer variable
LL | func(|| {
| -- captured by this `FnMut` closure
LL | // Shouldn't suggest `move ||.as_ref()` here
LL | move || {
| ^^^^^^^ `var` is moved here
LL |
LL | var = Some(NotCopyable);
| ---
| |
| variable moved due to use in closure
| move occurs because `var` has type `Option<NotCopyable>`, which does not implement the `Copy` trait
| --- variable moved due to use in closure

error[E0507]: cannot move out of `var`, a captured variable in an `FnMut` closure
--> $DIR/option-content-move2.rs:21:9
|
LL | let mut var = None;
| ------- captured outer variable
| ------- ---- move occurs because `var` has type `Option<NotCopyableButCloneable>`, which does not implement the `Copy` trait
| |
| captured outer variable
LL | func(|| {
| -- captured by this `FnMut` closure
LL | // Shouldn't suggest `move ||.as_ref()` nor to `clone()` here
LL | move || {
| ^^^^^^^ `var` is moved here
LL |
LL | var = Some(NotCopyableButCloneable);
| ---
| |
| variable moved due to use in closure
| move occurs because `var` has type `Option<NotCopyableButCloneable>`, which does not implement the `Copy` trait
| --- variable moved due to use in closure

error: aborting due to 2 previous errors

Expand Down
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