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Rollup merge of #144200 - estebank:dont-point-at-closure, r=lcnr

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Tweak output for non-`Clone` values moved into closures

When we encounter a non-`Clone` value being moved into a closure, try to find the corresponding type of the binding being moved, if it is a `let`-binding or a function parameter. If any of those cases, we point at them with the note explaining that the type is not `Copy`, instead of giving that label to the place where it is captured. When it is a `let`-binding with no explicit type, we point at the initializer (if it fits in a single line).

```
error[E0507]: cannot move out of `foo`, a captured variable in an `Fn` closure
  --> f111.rs:14:25
   |
13 | fn do_stuff(foo: Option<Foo>) {
   |             ---  ----------- move occurs because `foo` has type `Option<Foo>`, which does not implement the `Copy` trait
   |             |
   |             captured outer variable
14 |     require_fn_trait(|| async {
   |                      -- ^^^^^ `foo` is moved here
   |                      |
   |                      captured by this `Fn` closure
15 |         if foo.map_or(false, |f| f.foo()) {
   |            --- variable moved due to use in coroutine
```

instead of

```
error[E0507]: cannot move out of `foo`, a captured variable in an `Fn` closure
  --> f111.rs:14:25
   |
13 | fn do_stuff(foo: Option<Foo>) {
   |             --- captured outer variable
14 |     require_fn_trait(|| async {
   |                      -- ^^^^^ `foo` is moved here
   |                      |
   |                      captured by this `Fn` closure
15 |         if foo.map_or(false, |f| f.foo()) {
   |            ---
   |            |
   |            variable moved due to use in coroutine
   |            move occurs because `foo` has type `Option<Foo>`, which does not implement the `Copy` trait
```
This commit is contained in:
Matthias Krüger
2025-07-25 11:16:36 +02:00
committed by GitHub
parent dfbd0c4e5a 6237e735c4
commit 33a9e4f821
12 changed files with 149 additions and 100 deletions
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136
compiler/rustc_borrowck/src/diagnostics/move_errors.rs
View File

@@ -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
@@ -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(
span,
"Type may implement copy, but there is no other error.",
);
return;
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,
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);
}
@@ -483,7 +474,8 @@ 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() {
@@ -496,7 +488,7 @@ 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);
@@ -606,7 +598,7 @@ 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}`"),
@@ -623,6 +615,36 @@ 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,
@@ -630,12 +652,22 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
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);
}

7
tests/ui/async-await/async-closures/closure-shim-borrowck-error.stderr
View File

@@ -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

5
tests/ui/async-await/async-closures/move-out-of-ref.stderr
View File

@@ -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

6
tests/ui/borrowck/borrowck-in-static.stderr
View File

@@ -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
|

10
tests/ui/borrowck/borrowck-move-by-capture.stderr
View File

@@ -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

7
tests/ui/borrowck/issue-103624.stderr
View File

@@ -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

6
tests/ui/issues/issue-4335.stderr
View File

@@ -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
|

6
tests/ui/moves/moves-based-on-type-move-out-of-closure-env-issue-1965.stderr
View File

@@ -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
|

6
tests/ui/nll/issue-52663-span-decl-captured-variable.stderr
View File

@@ -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
|

18
tests/ui/suggestions/option-content-move2.stderr
View File

@@ -2,7 +2,9 @@ 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
@@ -10,16 +12,15 @@ 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
@@ -27,10 +28,7 @@ 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

18
tests/ui/suggestions/option-content-move3.stderr
View File

@@ -26,17 +26,16 @@ error[E0507]: cannot move out of `var`, a captured variable in an `FnMut` closur
--> $DIR/option-content-move3.rs:12:9
|
LL | let var = NotCopyable;
| --- captured outer variable
| --- ----------- move occurs because `var` has type `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 | let x = var;
| ---
| |
| variable moved due to use in closure
| move occurs because `var` has type `NotCopyable`, which does not implement the `Copy` trait
| --- variable moved due to use in closure
|
note: if `NotCopyable` implemented `Clone`, you could clone the value
--> $DIR/option-content-move3.rs:2:1
@@ -67,17 +66,16 @@ error[E0507]: cannot move out of `var`, a captured variable in an `FnMut` closur
--> $DIR/option-content-move3.rs:23:9
|
LL | let var = NotCopyableButCloneable;
| --- captured outer variable
| --- ----------------------- move occurs because `var` has type `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()` here
LL | move || {
| ^^^^^^^ `var` is moved here
LL | let x = var;
| ---
| |
| variable moved due to use in closure
| move occurs because `var` has type `NotCopyableButCloneable`, which does not implement the `Copy` trait
| --- variable moved due to use in closure
|
help: consider cloning the value before moving it into the closure
|

24
tests/ui/unboxed-closures/unboxed-closure-illegal-move.stderr
View File

@@ -2,9 +2,11 @@ error[E0507]: cannot move out of `x`, a captured variable in an `Fn` closure
--> $DIR/unboxed-closure-illegal-move.rs:15:31
|
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 | let f = to_fn(|| drop(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
|
@@ -17,9 +19,11 @@ error[E0507]: cannot move out of `x`, a captured variable in an `FnMut` closure
--> $DIR/unboxed-closure-illegal-move.rs:19:35
|
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 | let f = to_fn_mut(|| drop(x));
| -- ^ move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
| -- ^ `x` is moved here
| |
| captured by this `FnMut` closure
|
@@ -32,9 +36,11 @@ error[E0507]: cannot move out of `x`, a captured variable in an `Fn` closure
--> $DIR/unboxed-closure-illegal-move.rs:28:36
|
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 | let f = to_fn(move || drop(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
@@ -42,9 +48,11 @@ error[E0507]: cannot move out of `x`, a captured variable in an `FnMut` closure
--> $DIR/unboxed-closure-illegal-move.rs:32:40
|
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 | let f = to_fn_mut(move || drop(x));
| ------- ^ move occurs because `x` has type `Box<i32>`, which does not implement the `Copy` trait
| ------- ^ `x` is moved here
| |
| captured by this `FnMut` closure