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Fix End-user description not implemented for field access on `TyClosure #45938

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merged 2 commits into from
Nov 15, 2017
Merged

Fix End-user description not implemented for field access on `TyClosure #45938

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a6d691b
Fix End-user description not implemented for field access on `TyClosure
vramana Nov 11, 2017
5144d32
Fix printing of upvar in closures
vramana Nov 12, 2017
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87 changes: 56 additions & 31 deletions src/librustc_mir/borrow_check.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1021,7 +1021,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
access_lvalue: (ShallowOrDeep, &Lvalue<'tcx>),
flow_state: &InProgress<'b, 'gcx, 'tcx>,
mut op: F)
where F: FnMut(&mut Self, BorrowIndex, &BorrowData<'tcx>, &Lvalue) -> Control
where F: FnMut(&mut Self, BorrowIndex, &BorrowData<'tcx>, &Lvalue<'tcx>) -> Control
{
let (access, lvalue) = access_lvalue;

Expand Down Expand Up @@ -1248,7 +1248,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
fn report_use_of_moved_or_uninitialized(&mut self,
_context: Context,
desired_action: &str,
(lvalue, span): (&Lvalue, Span),
(lvalue, span): (&Lvalue<'tcx>, Span),
mpi: MovePathIndex,
curr_move_out: &IdxSetBuf<MoveOutIndex>) {

Expand Down Expand Up @@ -1290,8 +1290,8 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>

fn report_move_out_while_borrowed(&mut self,
_context: Context,
(lvalue, span): (&Lvalue, Span),
borrow: &BorrowData) {
(lvalue, span): (&Lvalue<'tcx>, Span),
borrow: &BorrowData<'tcx>) {
self.tcx.cannot_move_when_borrowed(span,
&self.describe_lvalue(lvalue),
Origin::Mir)
Expand All @@ -1305,8 +1305,8 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>

fn report_use_while_mutably_borrowed(&mut self,
_context: Context,
(lvalue, span): (&Lvalue, Span),
borrow : &BorrowData) {
(lvalue, span): (&Lvalue<'tcx>, Span),
borrow : &BorrowData<'tcx>) {

let mut err = self.tcx.cannot_use_when_mutably_borrowed(
span, &self.describe_lvalue(lvalue),
Expand Down Expand Up @@ -1382,8 +1382,8 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>

fn report_conflicting_borrow(&mut self,
context: Context,
common_prefix: &Lvalue,
(lvalue, span): (&Lvalue, Span),
common_prefix: &Lvalue<'tcx>,
(lvalue, span): (&Lvalue<'tcx>, Span),
gen_borrow_kind: BorrowKind,
issued_borrow: &BorrowData,
end_issued_loan_span: Option<Span>) {
Expand Down Expand Up @@ -1453,7 +1453,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>

fn report_illegal_mutation_of_borrowed(&mut self,
_: Context,
(lvalue, span): (&Lvalue, Span),
(lvalue, span): (&Lvalue<'tcx>, Span),
loan: &BorrowData) {
let mut err = self.tcx.cannot_assign_to_borrowed(
span, self.retrieve_borrow_span(loan), &self.describe_lvalue(lvalue), Origin::Mir);
Expand All @@ -1463,7 +1463,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>

fn report_illegal_reassignment(&mut self,
_context: Context,
(lvalue, span): (&Lvalue, Span),
(lvalue, span): (&Lvalue<'tcx>, Span),
assigned_span: Span) {
self.tcx.cannot_reassign_immutable(span,
&self.describe_lvalue(lvalue),
Expand All @@ -1474,7 +1474,9 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
.emit();
}

fn report_assignment_to_static(&mut self, _context: Context, (lvalue, span): (&Lvalue, Span)) {
fn report_assignment_to_static(&mut self,
_context: Context,
(lvalue, span): (&Lvalue<'tcx>, Span)) {
let mut err = self.tcx.cannot_assign_static(
span, &self.describe_lvalue(lvalue), Origin::Mir);
err.emit();
Expand All @@ -1483,14 +1485,17 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>

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 {
fn describe_lvalue(&self, lvalue: &Lvalue<'tcx>) -> String {
let mut buf = String::new();
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, autoderef: Option<bool>) {
fn append_lvalue_to_string(&self,
lvalue: &Lvalue<'tcx>,
buf: &mut String,
autoderef: Option<bool>) {
match *lvalue {
Lvalue::Local(local) => {
self.append_local_to_string(local, buf, "_");
Expand All @@ -1500,41 +1505,50 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
}
Lvalue::Projection(ref proj) => {
let mut autoderef = autoderef.unwrap_or(false);
let (prefix, suffix, index_operand) = match proj.elem {

match proj.elem {
ProjectionElem::Deref => {
if autoderef {
("", format!(""), None)
self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
} else {
("(*", format!(")"), None)
buf.push_str(&"(*");
self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
buf.push_str(&")");
}
},
ProjectionElem::Downcast(..) =>
("", format!(""), None), // (dont emit downcast info)
ProjectionElem::Downcast(..) => {
self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
},
ProjectionElem::Field(field, _ty) => {
autoderef = true;
("", format!(".{}", self.describe_field(&proj.base, field.index())), None)
let is_projection_from_ty_closure = proj.base.ty(self.mir, self.tcx)
.to_ty(self.tcx).is_closure();

let field_name = self.describe_field(&proj.base, field.index());
if is_projection_from_ty_closure {
buf.push_str(&format!("{}", field_name));
} else {
self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
buf.push_str(&format!(".{}", field_name));
}
},
ProjectionElem::Index(index) => {
autoderef = true;
("", format!(""), Some(index))

self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
buf.push_str("[");
self.append_local_to_string(index, buf, "..");
buf.push_str("]");
},
ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {
autoderef = true;
// Since it isn't possible to borrow an element on a particular index and
// then use another while the borrow is held, don't output indices details
// to avoid confusing the end-user
("", format!("[..]"), None)
self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
buf.push_str(&"[..]");
},
};
buf.push_str(prefix);
self.append_lvalue_to_string(&proj.base, buf, Some(autoderef));
if let Some(index) = index_operand {
buf.push_str("[");
self.append_local_to_string(index, buf, "..");
buf.push_str("]");
} else {
buf.push_str(&suffix);
}
}
}
}
Expand All @@ -1549,6 +1563,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
}
}

// FIXME Instead of passing usize, Field should be passed
// End-user visible description of the `field_index`nth field of `base`
fn describe_field(&self, base: &Lvalue, field_index: usize) -> String {
match *base {
Expand Down Expand Up @@ -1600,7 +1615,17 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx>
},
ty::TyArray(ty, _) | ty::TySlice(ty) => {
self.describe_field_from_ty(&ty, field_index)
}
},
ty::TyClosure(closure_def_id, _) => {
// Convert the def-id into a node-id. node-ids are only valid for
// the local code in the current crate, so this returns an `Option` in case
// the closure comes from another crate. But in that case we wouldn't
// be borrowck'ing it, so we can just unwrap:
let node_id = self.tcx.hir.as_local_node_id(closure_def_id).unwrap();
let freevar = self.tcx.with_freevars(node_id, |fv| fv[field_index]);

self.tcx.hir.name(freevar.var_id()).to_string()
}
_ => {
// Might need a revision when the fields in trait RFC is implemented
// (https://github.com/rust-lang/rfcs/pull/1546)
Expand Down
24 changes: 24 additions & 0 deletions src/test/compile-fail/borrowck/borrowck-describe-lvalue.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -327,4 +327,28 @@ fn main() {
_ => panic!("other case")
}
}
// Field from upvar
{
let mut x = 0;
|| {
let y = &mut x;
&mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time
//[mir]~^ ERROR cannot borrow `**x` as mutable more than once at a time (Ast)
//[mir]~| ERROR cannot borrow `(*x)` as mutable more than once at a time (Mir)
*y = 1;
};
}
// Field from upvar nested
{
let mut x = 0;
|| {
|| {
let y = &mut x;
&mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time
//[mir]~^ ERROR cannot borrow `**x` as mutable more than once at a time (Ast)
//[mir]~| ERROR cannot borrow `(*x)` as mutable more than once at a time (Mir)
*y = 1;
}
};
}
}