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suggest adding a local for vector to fix borrowck errors

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This commit is contained in:
Takayuki Maeda 2022-04-08 23:17:57 +09:00
parent dc1f8298ef
commit 71fea61bc9
6 changed files with 109 additions and 9 deletions
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40
compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
View File

@ -785,13 +785,22 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
issued_borrow: &BorrowData<'tcx>,
explanation: BorrowExplanation,
) {
let used_in_call =
matches!(explanation, BorrowExplanation::UsedLater(LaterUseKind::Call, _call_span, _));
let used_in_call = matches!(
explanation,
BorrowExplanation::UsedLater(LaterUseKind::Call | LaterUseKind::Other, _call_span, _)
);
if !used_in_call {
debug!("not later used in call");
return;
}
let use_span =
if let BorrowExplanation::UsedLater(LaterUseKind::Other, use_span, _) = explanation {
Some(use_span)
} else {
None
};
let outer_call_loc =
if let TwoPhaseActivation::ActivatedAt(loc) = issued_borrow.activation_location {
loc
@ -835,7 +844,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
debug!("===> outer_call_loc = {:?}, inner_call_loc = {:?}", outer_call_loc, inner_call_loc);
let inner_call_span = inner_call_term.source_info.span;
let outer_call_span = outer_call_stmt.either(|s| s.source_info, |t| t.source_info).span;
let outer_call_span = match use_span {
Some(span) => span,
None => outer_call_stmt.either(|s| s.source_info, |t| t.source_info).span,
};
if outer_call_span == inner_call_span || !outer_call_span.contains(inner_call_span) {
// FIXME: This stops the suggestion in some cases where it should be emitted.
// Fix the spans for those cases so it's emitted correctly.
@ -845,8 +857,20 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
);
return;
}
err.span_help(inner_call_span, "try adding a local storing this argument...");
err.span_help(outer_call_span, "...and then using that local as the argument to this call");
err.span_help(
inner_call_span,
&format!(
"try adding a local storing this{}...",
if use_span.is_some() { "" } else { " argument" }
),
);
err.span_help(
outer_call_span,
&format!(
"...and then using that local {}",
if use_span.is_some() { "here" } else { "as the argument to this call" }
),
);
}
fn suggest_split_at_mut_if_applicable(
@ -1912,10 +1936,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
} else {
"cannot assign twice to immutable variable"
};
if span != assigned_span {
if !from_arg {
err.span_label(assigned_span, format!("first assignment to {}", place_description));
}
if span != assigned_span && !from_arg {
err.span_label(assigned_span, format!("first assignment to {}", place_description));
}
if let Some(decl) = local_decl
&& let Some(name) = local_name

4
src/test/ui/borrowck/suggest-local-var-for-vector.rs Normal file
View File

@ -0,0 +1,4 @@
fn main() {
let mut vec = vec![0u32; 420];
vec[vec.len() - 1] = 123; //~ ERROR cannot borrow `vec` as immutable because it is also borrowed as mutable
}

24
src/test/ui/borrowck/suggest-local-var-for-vector.stderr Normal file
View File

@ -0,0 +1,24 @@
error[E0502]: cannot borrow `vec` as immutable because it is also borrowed as mutable
--> $DIR/suggest-local-var-for-vector.rs:3:9
|
LL | vec[vec.len() - 1] = 123;
| ----^^^^^^^^^-----
| | |
| | immutable borrow occurs here
| mutable borrow occurs here
| mutable borrow later used here
|
help: try adding a local storing this...
--> $DIR/suggest-local-var-for-vector.rs:3:9
|
LL | vec[vec.len() - 1] = 123;
| ^^^^^^^^^
help: ...and then using that local here
--> $DIR/suggest-local-var-for-vector.rs:3:5
|
LL | vec[vec.len() - 1] = 123;
| ^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0502`.

4
src/test/ui/borrowck/suggest-storing-local-var-for-vector.rs Normal file
View File

@ -0,0 +1,4 @@
fn main() {
let mut vec = vec![0u32; 420];
vec[vec.len() - 1] = 123; //~ ERROR cannot borrow `vec` as immutable because it is also borrowed as mutable
}

24
src/test/ui/borrowck/suggest-storing-local-var-for-vector.stderr Normal file
View File

@ -0,0 +1,24 @@
error[E0502]: cannot borrow `vec` as immutable because it is also borrowed as mutable
--> $DIR/suggest-storing-local-var-for-vector.rs:3:9
|
LL | vec[vec.len() - 1] = 123;
| ----^^^^^^^^^-----
| | |
| | immutable borrow occurs here
| mutable borrow occurs here
| mutable borrow later used here
|
help: try adding a local storing this...
--> $DIR/suggest-storing-local-var-for-vector.rs:3:9
|
LL | vec[vec.len() - 1] = 123;
| ^^^^^^^^^
help: ...and then using that local here
--> $DIR/suggest-storing-local-var-for-vector.rs:3:5
|
LL | vec[vec.len() - 1] = 123;
| ^^^^^^^^^^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0502`.

22
src/test/ui/borrowck/two-phase-nonrecv-autoref.nll.stderr
View File

@ -54,6 +54,17 @@ LL | i[i[3]] = 4;
| | immutable borrow occurs here
| mutable borrow occurs here
| mutable borrow later used here
|
help: try adding a local storing this...
--> $DIR/two-phase-nonrecv-autoref.rs:138:7
|
LL | i[i[3]] = 4;
| ^^^^
help: ...and then using that local here
--> $DIR/two-phase-nonrecv-autoref.rs:138:5
|
LL | i[i[3]] = 4;
| ^^^^^^^
error[E0502]: cannot borrow `i` as immutable because it is also borrowed as mutable
--> $DIR/two-phase-nonrecv-autoref.rs:143:7
@ -64,6 +75,17 @@ LL | i[i[3]] = i[4];
| | immutable borrow occurs here
| mutable borrow occurs here
| mutable borrow later used here
|
help: try adding a local storing this...
--> $DIR/two-phase-nonrecv-autoref.rs:143:7
|
LL | i[i[3]] = i[4];
| ^^^^
help: ...and then using that local here
--> $DIR/two-phase-nonrecv-autoref.rs:143:5
|
LL | i[i[3]] = i[4];
| ^^^^^^^
error: aborting due to 7 previous errors