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mir-borrowck: print values in error messages in the same way that the AST borrowck

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- Print fields with `.name` rather than `.<num>`
- Autoderef values if followed by a field or an index
This commit is contained in:
Basile Desloges 2017-10-02 19:36:58 +02:00
parent a8feaee5b6
commit aa78919733
1 changed files with 91 additions and 10 deletions
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101
src/librustc_mir/borrow_check.rs
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@ -1053,12 +1053,12 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
// End-user visible description of `lvalue`
fn describe_lvalue(&self, lvalue: &Lvalue) -> String {
let mut buf = String::new();
self.append_lvalue_to_string(lvalue, &mut buf);
self.append_lvalue_to_string(lvalue, &mut buf, None);
buf
}
// Appends end-user visible description of `lvalue` to `buf`.
fn append_lvalue_to_string(&self, lvalue: &Lvalue, buf: &mut String) {
fn append_lvalue_to_string(&self, lvalue: &Lvalue, buf: &mut String, autoderef: Option<bool>) {
match *lvalue {
Lvalue::Local(local) => {
let local = &self.mir.local_decls[local];
@ -1071,15 +1071,25 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
buf.push_str(&format!("{}", &self.tcx.item_name(static_.def_id)));
}
Lvalue::Projection(ref proj) => {
let mut autoderef = autoderef.unwrap_or(false);
let (prefix, suffix, index_operand) = match proj.elem {
ProjectionElem::Deref =>
("(*", format!(")"), None),
ProjectionElem::Deref => {
if autoderef {
("", format!(""), None)
} else {
("(*", format!(")"), None)
}
},
ProjectionElem::Downcast(..) =>
("", format!(""), None), // (dont emit downcast info)
ProjectionElem::Field(field, _ty) =>
("", format!(".{}", field.index()), None), // FIXME: report name of field
ProjectionElem::Index(index) =>
("", format!(""), Some(index)),
ProjectionElem::Field(field, _ty) => {
autoderef = true;
("", format!(".{}", self.describe_field(&proj.base, field.index())), None)
},
ProjectionElem::Index(index) => {
autoderef = true;
("", format!(""), Some(index))
},
ProjectionElem::ConstantIndex { offset, min_length, from_end: true } =>
("", format!("[{} of {}]", offset, min_length), None),
ProjectionElem::ConstantIndex { offset, min_length, from_end: false } =>
@ -1092,10 +1102,10 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
("", format!("[{}:-{}]", from, to), None),
};
buf.push_str(prefix);
self.append_lvalue_to_string(&proj.base, buf);
self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
if let Some(index) = index_operand {
buf.push_str("[");
self.append_lvalue_to_string(&Lvalue::Local(index), buf);
self.append_lvalue_to_string(&Lvalue::Local(index), buf, None);
buf.push_str("]");
} else {
buf.push_str(&suffix);
@ -1104,6 +1114,77 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
}
}
// End-user visible description of the `field_index`nth field of `base`
fn describe_field(&self, base: &Lvalue, field_index: usize) -> String {
match *base {
Lvalue::Local(local) => {
let local = &self.mir.local_decls[local];
self.describe_field_from_ty(&local.ty, field_index)
},
Lvalue::Static(ref static_) => {
self.describe_field_from_ty(&static_.ty, field_index)
},
Lvalue::Projection(ref proj) => {
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);
format!("<field>{}", field_index)
},
ProjectionElem::Index(..) => {
debug!("End-user description not implemented for field of projection {:?}",
proj);
format!("<index>{}", field_index)
},
ProjectionElem::ConstantIndex { .. } => {
debug!("End-user description not implemented for field of projection {:?}",
proj);
format!("<constant_index>{}", field_index)
},
ProjectionElem::Subslice { .. } => {
debug!("End-user description not implemented for field of projection {:?}",
proj);
format!("<subslice>{}", field_index)
}
}
}
}
}
// End-user visible description of the `field_index`nth field of `ty`
fn describe_field_from_ty(&self, ty: &ty::Ty, field_index: usize) -> String {
if ty.is_box() {
// If the type is a box, the field is described from the boxed type
self.describe_field_from_ty(&ty.boxed_ty(), field_index)
}
else {
match ty.sty {
ty::TyAdt(def, _) => {
if def.is_enum() {
format!("{}", field_index)
}
else {
format!("{}", def.struct_variant().fields[field_index].name)
}
},
ty::TyTuple(_, _) => {
format!("{}", field_index)
},
_ => {
debug!("End-user description not implemented for field of type {:?}", ty.sty);
format!("<ty>{}", field_index)
}
}
}
}
// Retrieve span of given borrow from the current MIR representation
fn retrieve_borrow_span(&self, borrow: &BorrowData) -> Span {
self.mir.basic_blocks()[borrow.location.block]