diff options
| -rw-r--r-- | compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs | 84 | ||||
| -rw-r--r-- | compiler/rustc_hir/src/hir.rs | 38 | ||||
| -rw-r--r-- | tests/ui/suggestions/suggest-split-at-mut.rs | 56 | ||||
| -rw-r--r-- | tests/ui/suggestions/suggest-split-at-mut.stderr | 80 |
4 files changed, 235 insertions, 23 deletions
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs index 40c49dcfab6..da58db57525 100644 --- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs +++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs @@ -1527,7 +1527,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow }, ) => { first_borrow_desc = "mutable "; - self.cannot_reborrow_already_borrowed( + let mut err = self.cannot_reborrow_already_borrowed( span, &desc_place, &msg_place, @@ -1537,7 +1537,15 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { "mutable", &msg_borrow, None, - ) + ); + self.suggest_slice_method_if_applicable( + &mut err, + place, + issued_borrow.borrowed_place, + span, + issued_span, + ); + err } ( BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow }, @@ -1555,6 +1563,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { &msg_borrow, None, ); + self.suggest_slice_method_if_applicable( + &mut err, + place, + issued_borrow.borrowed_place, + span, + issued_span, + ); self.suggest_binding_for_closure_capture_self(&mut err, &issued_spans); self.suggest_using_closure_argument_instead_of_capture( &mut err, @@ -1581,6 +1596,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { &mut err, place, issued_borrow.borrowed_place, + span, + issued_span, ); self.suggest_using_closure_argument_instead_of_capture( &mut err, @@ -2011,40 +2028,47 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { err: &mut Diag<'_>, place: Place<'tcx>, borrowed_place: Place<'tcx>, + span: Span, + issued_span: Span, ) { let tcx = self.infcx.tcx; let hir = tcx.hir(); + let has_split_at_mut = |ty: Ty<'tcx>| { + let ty = ty.peel_refs(); + match ty.kind() { + ty::Array(..) | ty::Slice(..) => true, + ty::Adt(def, _) if tcx.get_diagnostic_item(sym::Vec) == Some(def.did()) => true, + _ if ty == tcx.types.str_ => true, + _ => false, + } + }; if let ([ProjectionElem::Index(index1)], [ProjectionElem::Index(index2)]) | ( [ProjectionElem::Deref, ProjectionElem::Index(index1)], [ProjectionElem::Deref, ProjectionElem::Index(index2)], ) = (&place.projection[..], &borrowed_place.projection[..]) { + let decl1 = &self.body.local_decls[*index1]; + let decl2 = &self.body.local_decls[*index2]; + let mut note_default_suggestion = || { err.help( - "consider using `.split_at_mut(position)` or similar method to obtain \ - two mutable non-overlapping sub-slices", + "consider using `.split_at_mut(position)` or similar method to obtain two \ + mutable non-overlapping sub-slices", ) - .help("consider using `.swap(index_1, index_2)` to swap elements at the specified indices"); - }; - - let Some(body_id) = tcx.hir_node(self.mir_hir_id()).body_id() else { - note_default_suggestion(); - return; + .help( + "consider using `.swap(index_1, index_2)` to swap elements at the specified \ + indices", + ); }; - let mut expr_finder = - FindExprBySpan::new(self.body.local_decls[*index1].source_info.span, tcx); - expr_finder.visit_expr(hir.body(body_id).value); - let Some(index1) = expr_finder.result else { + let Some(index1) = self.find_expr(decl1.source_info.span) else { note_default_suggestion(); return; }; - expr_finder = FindExprBySpan::new(self.body.local_decls[*index2].source_info.span, tcx); - expr_finder.visit_expr(hir.body(body_id).value); - let Some(index2) = expr_finder.result else { + let Some(index2) = self.find_expr(decl2.source_info.span) else { note_default_suggestion(); return; }; @@ -2092,7 +2116,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { None } }) else { - note_default_suggestion(); + let hir::Node::Expr(parent) = tcx.parent_hir_node(index1.hir_id) else { return }; + let hir::ExprKind::Index(_, idx1, _) = parent.kind else { return }; + let hir::Node::Expr(parent) = tcx.parent_hir_node(index2.hir_id) else { return }; + let hir::ExprKind::Index(_, idx2, _) = parent.kind else { return }; + if !idx1.equivalent_for_indexing(idx2) { + err.help("use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices"); + } return; }; @@ -2102,7 +2132,25 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { format!("{obj_str}.swap({index1_str}, {index2_str})"), Applicability::MachineApplicable, ); + return; + } + let place_ty = PlaceRef::ty(&place.as_ref(), self.body, tcx).ty; + let borrowed_place_ty = PlaceRef::ty(&borrowed_place.as_ref(), self.body, tcx).ty; + if !has_split_at_mut(place_ty) && !has_split_at_mut(borrowed_place_ty) { + // Only mention `split_at_mut` on `Vec`, array and slices. + return; + } + let Some(index1) = self.find_expr(span) else { return }; + let hir::Node::Expr(parent) = tcx.parent_hir_node(index1.hir_id) else { return }; + let hir::ExprKind::Index(_, idx1, _) = parent.kind else { return }; + let Some(index2) = self.find_expr(issued_span) else { return }; + let hir::Node::Expr(parent) = tcx.parent_hir_node(index2.hir_id) else { return }; + let hir::ExprKind::Index(_, idx2, _) = parent.kind else { return }; + if idx1.equivalent_for_indexing(idx2) { + // `let a = &mut foo[0]` and `let b = &mut foo[0]`? Don't mention `split_at_mut` + return; } + err.help("use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices"); } /// Suggest using `while let` for call `next` on an iterator in a for loop. diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs index 2268905430a..1646ea50fb0 100644 --- a/compiler/rustc_hir/src/hir.rs +++ b/compiler/rustc_hir/src/hir.rs @@ -1811,6 +1811,44 @@ impl Expr<'_> { } } + /// Whether this and the `other` expression are the same for purposes of an indexing operation. + /// + /// This is only used for diagnostics to see if we have things like `foo[i]` where `foo` is + /// borrowed multiple times with `i`. + pub fn equivalent_for_indexing(&self, other: &Expr<'_>) -> bool { + match (self.kind, other.kind) { + (ExprKind::Lit(lit1), ExprKind::Lit(lit2)) => lit1.node == lit2.node, + ( + ExprKind::Path(QPath::LangItem(item1, _)), + ExprKind::Path(QPath::LangItem(item2, _)), + ) => item1 == item2, + ( + ExprKind::Path(QPath::Resolved(None, path1)), + ExprKind::Path(QPath::Resolved(None, path2)), + ) => path1.res == path2.res, + ( + ExprKind::Struct(QPath::LangItem(LangItem::RangeTo, _), [val1], None), + ExprKind::Struct(QPath::LangItem(LangItem::RangeTo, _), [val2], None), + ) + | ( + ExprKind::Struct(QPath::LangItem(LangItem::RangeToInclusive, _), [val1], None), + ExprKind::Struct(QPath::LangItem(LangItem::RangeToInclusive, _), [val2], None), + ) + | ( + ExprKind::Struct(QPath::LangItem(LangItem::RangeFrom, _), [val1], None), + ExprKind::Struct(QPath::LangItem(LangItem::RangeFrom, _), [val2], None), + ) => val1.expr.equivalent_for_indexing(val2.expr), + ( + ExprKind::Struct(QPath::LangItem(LangItem::Range, _), [val1, val3], None), + ExprKind::Struct(QPath::LangItem(LangItem::Range, _), [val2, val4], None), + ) => { + val1.expr.equivalent_for_indexing(val2.expr) + && val3.expr.equivalent_for_indexing(val4.expr) + } + _ => false, + } + } + pub fn method_ident(&self) -> Option<Ident> { match self.kind { ExprKind::MethodCall(receiver_method, ..) => Some(receiver_method.ident), diff --git a/tests/ui/suggestions/suggest-split-at-mut.rs b/tests/ui/suggestions/suggest-split-at-mut.rs index d294c20b824..61704abbd36 100644 --- a/tests/ui/suggestions/suggest-split-at-mut.rs +++ b/tests/ui/suggestions/suggest-split-at-mut.rs @@ -1,4 +1,4 @@ -fn main() { +fn foo() { let mut foo = [1, 2, 3, 4]; let a = &mut foo[2]; let b = &mut foo[3]; //~ ERROR cannot borrow `foo[_]` as mutable more than once at a time @@ -6,3 +6,57 @@ fn main() { *b = 6; println!("{:?} {:?}", a, b); } + +fn bar() { + let mut foo = [1,2,3,4]; + let a = &mut foo[..2]; + let b = &mut foo[2..]; //~ ERROR cannot borrow `foo` as mutable more than once at a time + a[0] = 5; + b[0] = 6; + println!("{:?} {:?}", a, b); +} + +fn baz() { + let mut foo = [1,2,3,4]; + let a = &foo[..2]; + let b = &mut foo[2..]; //~ ERROR cannot borrow `foo` as mutable because it is also borrowed as immutable + b[0] = 6; + println!("{:?} {:?}", a, b); +} + +fn qux() { + let mut foo = [1,2,3,4]; + let a = &mut foo[..2]; + let b = &foo[2..]; //~ ERROR cannot borrow `foo` as immutable because it is also borrowed as mutable + a[0] = 5; + println!("{:?} {:?}", a, b); +} + +fn bad() { + let mut foo = [1,2,3,4]; + let a = &foo[1]; + let b = &mut foo[2]; //~ ERROR cannot borrow `foo[_]` as mutable because it is also borrowed as immutable + *b = 6; + println!("{:?} {:?}", a, b); +} + +fn bat() { + let mut foo = [1,2,3,4]; + let a = &mut foo[1]; + let b = &foo[2]; //~ ERROR cannot borrow `foo[_]` as immutable because it is also borrowed as mutable + *a = 5; + println!("{:?} {:?}", a, b); +} + +fn ang() { + let mut foo = [1,2,3,4]; + let a = &mut foo[0..]; + let b = &foo[0..]; //~ ERROR cannot borrow `foo` as immutable because it is also borrowed as mutable + a[0] = 5; + println!("{:?} {:?}", a, b); +} + +fn main() { + foo(); + bar(); +} diff --git a/tests/ui/suggestions/suggest-split-at-mut.stderr b/tests/ui/suggestions/suggest-split-at-mut.stderr index c42f09e3201..4502ec1f393 100644 --- a/tests/ui/suggestions/suggest-split-at-mut.stderr +++ b/tests/ui/suggestions/suggest-split-at-mut.stderr @@ -8,9 +8,81 @@ LL | let b = &mut foo[3]; LL | *a = 5; | ------ first borrow later used here | - = help: consider using `.split_at_mut(position)` or similar method to obtain two mutable non-overlapping sub-slices - = help: consider using `.swap(index_1, index_2)` to swap elements at the specified indices + = help: use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices -error: aborting due to 1 previous error +error[E0499]: cannot borrow `foo` as mutable more than once at a time + --> $DIR/suggest-split-at-mut.rs:13:18 + | +LL | let a = &mut foo[..2]; + | --- first mutable borrow occurs here +LL | let b = &mut foo[2..]; + | ^^^ second mutable borrow occurs here +LL | a[0] = 5; + | ---- first borrow later used here + | + = help: use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices + +error[E0502]: cannot borrow `foo` as mutable because it is also borrowed as immutable + --> $DIR/suggest-split-at-mut.rs:22:18 + | +LL | let a = &foo[..2]; + | --- immutable borrow occurs here +LL | let b = &mut foo[2..]; + | ^^^ mutable borrow occurs here +LL | b[0] = 6; +LL | println!("{:?} {:?}", a, b); + | - immutable borrow later used here + | + = help: use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices + +error[E0502]: cannot borrow `foo` as immutable because it is also borrowed as mutable + --> $DIR/suggest-split-at-mut.rs:30:14 + | +LL | let a = &mut foo[..2]; + | --- mutable borrow occurs here +LL | let b = &foo[2..]; + | ^^^ immutable borrow occurs here +LL | a[0] = 5; + | ---- mutable borrow later used here + | + = help: use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices + +error[E0502]: cannot borrow `foo[_]` as mutable because it is also borrowed as immutable + --> $DIR/suggest-split-at-mut.rs:38:13 + | +LL | let a = &foo[1]; + | ------- immutable borrow occurs here +LL | let b = &mut foo[2]; + | ^^^^^^^^^^^ mutable borrow occurs here +LL | *b = 6; +LL | println!("{:?} {:?}", a, b); + | - immutable borrow later used here + | + = help: use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices + +error[E0502]: cannot borrow `foo[_]` as immutable because it is also borrowed as mutable + --> $DIR/suggest-split-at-mut.rs:46:13 + | +LL | let a = &mut foo[1]; + | ----------- mutable borrow occurs here +LL | let b = &foo[2]; + | ^^^^^^^ immutable borrow occurs here +LL | *a = 5; + | ------ mutable borrow later used here + | + = help: use `.split_at_mut(position)` to obtain two mutable non-overlapping sub-slices + +error[E0502]: cannot borrow `foo` as immutable because it is also borrowed as mutable + --> $DIR/suggest-split-at-mut.rs:54:14 + | +LL | let a = &mut foo[0..]; + | --- mutable borrow occurs here +LL | let b = &foo[0..]; + | ^^^ immutable borrow occurs here +LL | a[0] = 5; + | ---- mutable borrow later used here + +error: aborting due to 7 previous errors -For more information about this error, try `rustc --explain E0499`. +Some errors have detailed explanations: E0499, E0502. +For more information about an error, try `rustc --explain E0499`. |