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mir-borrowck: Implement end-user output for field of downcast projection

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This commit is contained in:
Basile Desloges 2017-10-06 17:24:23 +02:00
parent 0241ea45b2
commit f35c4e3aa1
2 changed files with 22 additions and 5 deletions
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7
src/librustc_mir/borrow_check.rs
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@ -1125,11 +1125,6 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
match proj.elem {
ProjectionElem::Deref =>
self.describe_field(&proj.base, field_index),
ProjectionElem::Downcast(..) => {
debug!("End-user description not implemented for field of projection {:?}",
proj);
format!("<downcast>{}", field_index)
},
ProjectionElem::Field(..) => {
debug!("End-user description not implemented for field of projection {:?}",
proj);
@ -1145,6 +1140,8 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
proj);
format!("<constant_index>{}", field_index)
},
ProjectionElem::Downcast(def, variant_index) =>
format!("{}", def.variants[variant_index].fields[field_index].name),
ProjectionElem::Subslice { .. } => {
debug!("End-user description not implemented for field of projection {:?}",
proj);

20
src/test/compile-fail/borrowck/borrowck-describe-lvalue.rs
View file

@ -233,4 +233,24 @@ fn main() {
_ => panic!("other case"),
}
}
// Downcasted field
{
enum E<X> { A(X), B { x: X } }
let mut e = E::A(3);
let _e = &mut e;
match e {
E::A(ref ax) =>
//[ast]~^ ERROR cannot borrow `e.0` as immutable because `e` is also borrowed as mutable
//[mir]~^^ ERROR cannot borrow `e.0` as immutable because `e` is also borrowed as mutable (Ast)
//[mir]~| ERROR cannot borrow `e.0` as immutable because it is also borrowed as mutable (Mir)
//[mir]~| ERROR cannot use `e` because it was mutably borrowed (Mir)
println!("e.ax: {:?}", ax),
E::B { x: ref bx } =>
//[ast]~^ ERROR cannot borrow `e.x` as immutable because `e` is also borrowed as mutable
//[mir]~^^ ERROR cannot borrow `e.x` as immutable because `e` is also borrowed as mutable (Ast)
//[mir]~| ERROR cannot borrow `e.x` as immutable because it is also borrowed as mutable (Mir)
println!("e.bx: {:?}", bx),
}
}
}