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Fix erroneous error note when using field after move #51688

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Merged
merged 2 commits into from
Jun 25, 2018
Merged

Fix erroneous error note when using field after move #51688

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ad612d6
Fix erroneous error note when using field after move
spastorino Jun 21, 2018
1dae309
Run rustfmt
spastorino Jun 22, 2018
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2 changes: 1 addition & 1 deletion src/librustc_borrowck/borrowck/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -680,7 +680,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
let mut err = self.cannot_act_on_moved_value(use_span,
verb,
msg,
&format!("{}", nl),
Some(format!("{}", nl)),
Origin::Ast);
let need_note = match lp.ty.sty {
ty::TypeVariants::TyClosure(id, _) => {
Expand Down
108 changes: 85 additions & 23 deletions src/librustc_mir/borrow_check/error_reporting.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,15 +52,17 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {

self.moved_error_reported.insert(root_place.clone());

let item_msg = match self.describe_place(place) {
let item_msg = match self.describe_place_with_options(place, IncludingDowncast(true)) {
Some(name) => format!("`{}`", name),
None => "value".to_owned(),
};
self.tcx
.cannot_act_on_uninitialized_variable(
span,
desired_action.as_noun(),
&self.describe_place(place).unwrap_or("_".to_owned()),
&self
.describe_place_with_options(place, IncludingDowncast(true))
.unwrap_or("_".to_owned()),
Origin::Mir,
)
.span_label(span, format!("use of possibly uninitialized {}", item_msg))
Expand All @@ -72,14 +74,17 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
span,
desired_action.as_noun(),
msg,
&self.describe_place(place).unwrap_or("_".to_owned()),
self.describe_place_with_options(&place, IncludingDowncast(true)),
Origin::Mir,
);

let mut is_loop_move = false;
for moi in mois {
for moi in &mois {
let move_msg = ""; //FIXME: add " (into closure)"
let move_span = self.mir.source_info(self.move_data.moves[*moi].source).span;
let move_span = self
.mir
.source_info(self.move_data.moves[**moi].source)
.span;
if span == move_span {
err.span_label(
span,
Expand Down Expand Up @@ -116,16 +121,23 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
};

if needs_note {
let note_msg = match self.describe_place(place) {
Some(name) => format!("`{}`", name),
None => "value".to_owned(),
};
let mpi = self.move_data.moves[*mois[0]].path;
let place = &self.move_data.move_paths[mpi].place;

if let Some(ty) = self.retrieve_type_for_place(place) {
let note_msg = match self
.describe_place_with_options(place, IncludingDowncast(true))
{
Some(name) => format!("`{}`", name),
None => "value".to_owned(),
};

err.note(&format!(
"move occurs because {} has type `{}`, \
which does not implement the `Copy` trait",
note_msg, ty
));
err.note(&format!(
"move occurs because {} has type `{}`, \
which does not implement the `Copy` trait",
note_msg, ty
));
}
}
}

Expand Down Expand Up @@ -644,8 +656,10 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
let local_decl = &self.mir.local_decls[*local];
if let Some(name) = local_decl.name {
if local_decl.can_be_made_mutable() {
err.span_label(local_decl.source_info.span,
format!("consider changing this to `mut {}`", name));
err.span_label(
local_decl.source_info.span,
format!("consider changing this to `mut {}`", name),
);
}
}
}
Expand All @@ -654,12 +668,26 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
}
}

pub(super) struct IncludingDowncast(bool);
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It's usually a bit more idiomatic to use an enum with the possible states, but this is still an improvement in readibility over a naked Boolean.

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Yeah, I think I prefer an enum, was just following @nikomatsakis suggestion. But I'm fine with either.


impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
// End-user visible description of `place` if one can be found. If the
// place is a temporary for instance, None will be returned.
pub(super) fn describe_place(&self, place: &Place<'tcx>) -> Option<String> {
self.describe_place_with_options(place, IncludingDowncast(false))
}

// End-user visible description of `place` if one can be found. If the
// place is a temporary for instance, None will be returned.
// `IncludingDowncast` parameter makes the function return `Err` if `ProjectionElem` is
// `Downcast` and `IncludingDowncast` is true
pub(super) fn describe_place_with_options(
&self,
place: &Place<'tcx>,
including_downcast: IncludingDowncast,
) -> Option<String> {
let mut buf = String::new();
match self.append_place_to_string(place, &mut buf, false) {
match self.append_place_to_string(place, &mut buf, false, &including_downcast) {
Ok(()) => Some(buf),
Err(()) => None,
}
Expand All @@ -671,6 +699,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
place: &Place<'tcx>,
buf: &mut String,
mut autoderef: bool,
including_downcast: &IncludingDowncast,
) -> Result<(), ()> {
match *place {
Place::Local(local) => {
Expand All @@ -692,15 +721,33 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
}
} else {
if autoderef {
self.append_place_to_string(&proj.base, buf, autoderef)?;
self.append_place_to_string(
&proj.base,
buf,
autoderef,
&including_downcast,
)?;
} else {
buf.push_str(&"*");
self.append_place_to_string(&proj.base, buf, autoderef)?;
self.append_place_to_string(
&proj.base,
buf,
autoderef,
&including_downcast,
)?;
}
}
}
ProjectionElem::Downcast(..) => {
self.append_place_to_string(&proj.base, buf, autoderef)?;
self.append_place_to_string(
&proj.base,
buf,
autoderef,
&including_downcast,
)?;
if including_downcast.0 {
return Err(());
}
}
ProjectionElem::Field(field, _ty) => {
autoderef = true;
Expand All @@ -711,14 +758,24 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
buf.push_str(&name);
} else {
let field_name = self.describe_field(&proj.base, field);
self.append_place_to_string(&proj.base, buf, autoderef)?;
self.append_place_to_string(
&proj.base,
buf,
autoderef,
&including_downcast,
)?;
buf.push_str(&format!(".{}", field_name));
}
}
ProjectionElem::Index(index) => {
autoderef = true;

self.append_place_to_string(&proj.base, buf, autoderef)?;
self.append_place_to_string(
&proj.base,
buf,
autoderef,
&including_downcast,
)?;
buf.push_str("[");
if let Err(_) = self.append_local_to_string(index, buf) {
buf.push_str("..");
Expand All @@ -730,7 +787,12 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
// Since it isn't possible to borrow an element on a particular index and
// then use another while the borrow is held, don't output indices details
// to avoid confusing the end-user
self.append_place_to_string(&proj.base, buf, autoderef)?;
self.append_place_to_string(
&proj.base,
buf,
autoderef,
&including_downcast,
)?;
buf.push_str(&"[..]");
}
};
Expand Down
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