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When encountering move error on an Option, suggest using as_ref

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This commit is contained in:
Esteban Küber 2019-05-24 19:10:00 -07:00
parent dec4c5201f
commit 4b0963653e
4 changed files with 137 additions and 76 deletions
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159
src/librustc_mir/borrow_check/move_errors.rs
View File

@ -242,12 +242,7 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
let (mut err, err_span) = {
let (span, original_path, kind): (Span, &Place<'tcx>, &IllegalMoveOriginKind<'_>) =
match error {
GroupedMoveError::MovesFromPlace {
span,
ref original_path,
ref kind,
..
} |
GroupedMoveError::MovesFromPlace { span, ref original_path, ref kind, .. } |
GroupedMoveError::MovesFromValue { span, ref original_path, ref kind, .. } |
GroupedMoveError::OtherIllegalMove { span, ref original_path, ref kind } => {
(span, original_path, kind)
@ -257,81 +252,93 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
debug!("report: original_path={:?} span={:?}, kind={:?} \
original_path.is_upvar_field_projection={:?}", original_path, span, kind,
self.is_upvar_field_projection(original_path));
(
match kind {
IllegalMoveOriginKind::Static => {
self.infcx.tcx.cannot_move_out_of(span, "static item", origin)
}
IllegalMoveOriginKind::BorrowedContent { target_place: place } => {
// Inspect the type of the content behind the
// borrow to provide feedback about why this
// was a move rather than a copy.
let ty = place.ty(self.mir, self.infcx.tcx).ty;
let is_upvar_field_projection =
self.prefixes(&original_path, PrefixSet::All)
.any(|p| self.is_upvar_field_projection(p).is_some());
debug!("report: ty={:?}", ty);
match ty.sty {
ty::Array(..) | ty::Slice(..) =>
self.infcx.tcx.cannot_move_out_of_interior_noncopy(
span, ty, None, origin
),
ty::Closure(def_id, closure_substs)
if def_id == self.mir_def_id && is_upvar_field_projection
=> {
let closure_kind_ty =
closure_substs.closure_kind_ty(def_id, self.infcx.tcx);
let closure_kind = closure_kind_ty.to_opt_closure_kind();
let place_description = match closure_kind {
Some(ty::ClosureKind::Fn) => {
"captured variable in an `Fn` closure"
}
Some(ty::ClosureKind::FnMut) => {
"captured variable in an `FnMut` closure"
}
Some(ty::ClosureKind::FnOnce) => {
bug!("closure kind does not match first argument type")
}
None => bug!("closure kind not inferred by borrowck"),
};
debug!("report: closure_kind_ty={:?} closure_kind={:?} \
place_description={:?}", closure_kind_ty, closure_kind,
place_description);
let mut diag = self.infcx.tcx.cannot_move_out_of(
span, place_description, origin);
for prefix in self.prefixes(&original_path, PrefixSet::All) {
if let Some(field) = self.is_upvar_field_projection(prefix) {
let upvar_hir_id = self.upvars[field.index()].var_hir_id;
let upvar_span = self.infcx.tcx.hir().span_by_hir_id(
upvar_hir_id);
diag.span_label(upvar_span, "captured outer variable");
break;
}
let err = match kind {
IllegalMoveOriginKind::Static => {
self.infcx.tcx.cannot_move_out_of(span, "static item", origin)
}
IllegalMoveOriginKind::BorrowedContent { target_place: place } => {
// Inspect the type of the content behind the
// borrow to provide feedback about why this
// was a move rather than a copy.
let ty = place.ty(self.mir, self.infcx.tcx).ty;
let is_upvar_field_projection =
self.prefixes(&original_path, PrefixSet::All)
.any(|p| self.is_upvar_field_projection(p).is_some());
debug!("report: ty={:?}", ty);
let mut err = match ty.sty {
ty::Array(..) | ty::Slice(..) =>
self.infcx.tcx.cannot_move_out_of_interior_noncopy(
span, ty, None, origin
),
ty::Closure(def_id, closure_substs)
if def_id == self.mir_def_id && is_upvar_field_projection
=> {
let closure_kind_ty =
closure_substs.closure_kind_ty(def_id, self.infcx.tcx);
let closure_kind = closure_kind_ty.to_opt_closure_kind();
let place_description = match closure_kind {
Some(ty::ClosureKind::Fn) => {
"captured variable in an `Fn` closure"
}
Some(ty::ClosureKind::FnMut) => {
"captured variable in an `FnMut` closure"
}
Some(ty::ClosureKind::FnOnce) => {
bug!("closure kind does not match first argument type")
}
None => bug!("closure kind not inferred by borrowck"),
};
debug!("report: closure_kind_ty={:?} closure_kind={:?} \
place_description={:?}", closure_kind_ty, closure_kind,
place_description);
diag
let mut diag = self.infcx.tcx.cannot_move_out_of(
span, place_description, origin);
for prefix in self.prefixes(&original_path, PrefixSet::All) {
if let Some(field) = self.is_upvar_field_projection(prefix) {
let upvar_hir_id = self.upvars[field.index()].var_hir_id;
let upvar_span = self.infcx.tcx.hir().span_by_hir_id(
upvar_hir_id);
diag.span_label(upvar_span, "captured outer variable");
break;
}
}
_ => {
let source = self.borrowed_content_source(place);
self.infcx.tcx.cannot_move_out_of(
span, &source.to_string(), origin
)
},
diag
}
_ => {
let source = self.borrowed_content_source(place);
self.infcx.tcx.cannot_move_out_of(
span, &source.to_string(), origin
)
},
};
let orig_path_ty = format!(
"{:?}",
original_path.ty(self.mir, self.infcx.tcx).ty,
);
let snippet = self.infcx.tcx.sess.source_map().span_to_snippet(span).unwrap();
if orig_path_ty.starts_with("std::option::Option") {
err.span_suggestion(
span,
"consider borrowing the `Option`'s content",
format!("{}.as_ref()", snippet),
Applicability::MaybeIncorrect,
);
}
IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
self.infcx.tcx
.cannot_move_out_of_interior_of_drop(span, ty, origin)
}
IllegalMoveOriginKind::InteriorOfSliceOrArray { ty, is_index } =>
self.infcx.tcx.cannot_move_out_of_interior_noncopy(
span, ty, Some(*is_index), origin
),
},
span,
)
err
}
IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
self.infcx.tcx
.cannot_move_out_of_interior_of_drop(span, ty, origin)
}
IllegalMoveOriginKind::InteriorOfSliceOrArray { ty, is_index } =>
self.infcx.tcx.cannot_move_out_of_interior_noncopy(
span, ty, Some(*is_index), origin
),
};
(err, span)
};
self.add_move_hints(error, &mut err, err_span);

21
src/test/ui/suggestions/option-content-move.fixed Normal file
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@ -0,0 +1,21 @@
//run-rustfix
pub struct LipogramCorpora {
selections: Vec<(char, Option<String>)>,
}
impl LipogramCorpora {
pub fn validate_all(&mut self) -> Result<(), char> {
for selection in &self.selections {
if selection.1.is_some() {
if selection.1.as_ref().unwrap().contains(selection.0) {
//~^ ERROR cannot move out of borrowed content
return Err(selection.0);
}
}
}
Ok(())
}
}
fn main() {}

21
src/test/ui/suggestions/option-content-move.rs Normal file
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@ -0,0 +1,21 @@
//run-rustfix
pub struct LipogramCorpora {
selections: Vec<(char, Option<String>)>,
}
impl LipogramCorpora {
pub fn validate_all(&mut self) -> Result<(), char> {
for selection in &self.selections {
if selection.1.is_some() {
if selection.1.unwrap().contains(selection.0) {
//~^ ERROR cannot move out of borrowed content
return Err(selection.0);
}
}
}
Ok(())
}
}
fn main() {}

12
src/test/ui/suggestions/option-content-move.stderr Normal file
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@ -0,0 +1,12 @@
error[E0507]: cannot move out of borrowed content
--> $DIR/option-content-move.rs:11:20
|
LL | if selection.1.unwrap().contains(selection.0) {
| ^^^^^^^^^^^
| |
| cannot move out of borrowed content
| help: consider borrowing the `Option`'s content: `selection.1.as_ref()`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0507`.