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Rollup merge of #80324 - Aaron1011:loop-move-fn-self, r=oli-obk

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Explain method-call move errors in loops

PR #73708 added a more detailed explanation of move errors that occur
due to a call to a method that takes `self`. This PR extends that logic
to work when a move error occurs due to a method call in the previous
iteration of a loop.
This commit is contained in:
Yuki Okushi 2021-01-12 07:59:10 +09:00 • committed by GitHub
commit 8e6472fe32
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15 changed files with 118 additions and 104 deletions
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162
compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs
View file

@ -151,95 +151,88 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
let move_msg = if move_spans.for_closure() { " into closure" } else { "" };
let loop_message = if location == move_out.source || move_site.traversed_back_edge {
", in previous iteration of loop"
} else {
""
};
if location == move_out.source {
err.span_label(
span,
format!(
"value {}moved{} here, in previous iteration of loop",
partially_str, move_msg
),
);
is_loop_move = true;
} else if move_site.traversed_back_edge {
}
if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans {
let place_name = self
.describe_place(moved_place.as_ref())
.map(|n| format!("`{}`", n))
.unwrap_or_else(|| "value".to_owned());
match kind {
FnSelfUseKind::FnOnceCall => {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to this call{}",
place_name, partially_str, loop_message
),
);
err.span_note(
var_span,
"this value implements `FnOnce`, which causes it to be moved when called",
);
}
FnSelfUseKind::Operator { self_arg } => {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to usage in operator{}",
place_name, partially_str, loop_message
),
);
if self.fn_self_span_reported.insert(fn_span) {
err.span_note(
self_arg.span,
"calling this operator moves the left-hand side",
);
}
}
FnSelfUseKind::Normal { self_arg, implicit_into_iter } => {
if implicit_into_iter {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to this implicit call to `.into_iter()`{}",
place_name, partially_str, loop_message
),
);
} else {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to this method call{}",
place_name, partially_str, loop_message
),
);
}
// Avoid pointing to the same function in multiple different
// error messages
if self.fn_self_span_reported.insert(self_arg.span) {
err.span_note(
self_arg.span,
&format!("this function takes ownership of the receiver `self`, which moves {}", place_name)
);
}
}
// Deref::deref takes &self, which cannot cause a move
FnSelfUseKind::DerefCoercion { .. } => unreachable!(),
}
} else {
err.span_label(
move_span,
format!(
"value {}moved{} here, in previous iteration of loop",
partially_str, move_msg
),
format!("value {}moved{} here{}", partially_str, move_msg, loop_message),
);
} else {
if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } =
move_spans
{
let place_name = self
.describe_place(moved_place.as_ref())
.map(|n| format!("`{}`", n))
.unwrap_or_else(|| "value".to_owned());
match kind {
FnSelfUseKind::FnOnceCall => {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to this call",
place_name, partially_str
),
);
err.span_note(
var_span,
"this value implements `FnOnce`, which causes it to be moved when called",
);
}
FnSelfUseKind::Operator { self_arg } => {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to usage in operator",
place_name, partially_str
),
);
if self.fn_self_span_reported.insert(fn_span) {
err.span_note(
self_arg.span,
"calling this operator moves the left-hand side",
);
}
}
FnSelfUseKind::Normal { self_arg, implicit_into_iter } => {
if implicit_into_iter {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to this implicit call to `.into_iter()`",
place_name, partially_str
),
);
} else {
err.span_label(
fn_call_span,
&format!(
"{} {}moved due to this method call",
place_name, partially_str
),
);
}
// Avoid pointing to the same function in multiple different
// error messages
if self.fn_self_span_reported.insert(self_arg.span) {
err.span_note(
self_arg.span,
&format!("this function consumes the receiver `self` by taking ownership of it, which moves {}", place_name)
);
}
}
// Deref::deref takes &self, which cannot cause a move
FnSelfUseKind::DerefCoercion { .. } => unreachable!(),
}
} else {
err.span_label(
move_span,
format!("value {}moved{} here", partially_str, move_msg),
);
// If the move error occurs due to a loop, don't show
// another message for the same span
if loop_message.is_empty() {
move_spans.var_span_label(
&mut err,
format!(
@ -250,6 +243,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
);
}
}
if let UseSpans::PatUse(span) = move_spans {
err.span_suggestion_verbose(
span.shrink_to_lo(),