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Don't suggest wrong snippet in closure #67247

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Dec 13, 2019
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16 changes: 12 additions & 4 deletions src/librustc_mir/borrow_check/diagnostics/move_errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -223,18 +223,24 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {

fn report(&mut self, error: GroupedMoveError<'tcx>) {
let (mut err, err_span) = {
let (span, original_path, kind): (Span, &Place<'tcx>, &IllegalMoveOriginKind<'_>) =
let (span, use_spans, original_path, kind,):
(
Span,
Option<UseSpans>,
&Place<'tcx>,
&IllegalMoveOriginKind<'_>,
) =
match error {
GroupedMoveError::MovesFromPlace { span, ref original_path, ref kind, .. } |
GroupedMoveError::MovesFromValue { span, ref original_path, ref kind, .. } => {
(span, original_path, kind)
(span, None, original_path, kind)
}
GroupedMoveError::OtherIllegalMove {
use_spans,
ref original_path,
ref kind
} => {
(use_spans.args_or_use(), original_path, kind)
(use_spans.args_or_use(), Some(use_spans), original_path, kind)
},
};
debug!("report: original_path={:?} span={:?}, kind={:?} \
Expand All @@ -250,6 +256,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
original_path,
target_place,
span,
use_spans,
)
}
IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
Expand Down Expand Up @@ -296,6 +303,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
move_place: &Place<'tcx>,
deref_target_place: &Place<'tcx>,
span: Span,
use_spans: Option<UseSpans>,
) -> DiagnosticBuilder<'a> {
// Inspect the type of the content behind the
// borrow to provide feedback about why this
Expand Down Expand Up @@ -416,7 +424,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
if let Ok(snippet) = self.infcx.tcx.sess.source_map().span_to_snippet(span) {
let is_option = move_ty.starts_with("std::option::Option");
let is_result = move_ty.starts_with("std::result::Result");
if is_option || is_result {
if (is_option || is_result) && use_spans.map_or(true, |v| !v.for_closure()) {
err.span_suggestion(
span,
&format!("consider borrowing the `{}`'s content", if is_option {
Expand Down
16 changes: 16 additions & 0 deletions src/test/ui/suggestions/option-content-move2.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
struct NotCopyable;

fn func<F: FnMut() -> H, H: FnMut()>(_: F) {}

fn parse() {
let mut var = None;
func(|| {
// Shouldn't suggest `move ||.as_ref()` here
move || {
//~^ ERROR: cannot move out of `var`
var = Some(NotCopyable);
}
});
}

fn main() {}
18 changes: 18 additions & 0 deletions src/test/ui/suggestions/option-content-move2.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
error[E0507]: cannot move out of `var`, a captured variable in an `FnMut` closure
--> $DIR/option-content-move2.rs:9:9
|
LL | let mut var = None;
| ------- captured outer variable
...
LL | move || {
| ^^^^^^^ move out of `var` occurs here
LL |
LL | var = Some(NotCopyable);
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Interestingly, suggesting var = Some(NotCopyable).as_ref(); or var= Some(&NotCopyable); could be reasonable, but I wouldn't go out of my way to emit either. The as_ref() suggestion is meant for people still getting their bearings with the language, and the kind of code that this PR protects against is unlikely to be written by that kind of user.

| ---
| |
| move occurs because `var` has type `std::option::Option<NotCopyable>`, which does not implement the `Copy` trait
| move occurs due to use in closure

error: aborting due to previous error

For more information about this error, try `rustc --explain E0507`.