Support unions in borrow checker

Add some more tests

Author: petrochenkov

src/librustc_borrowck/borrowck/fragments.rs

@@ -461,6 +461,10 @@ fn add_fragment_siblings_for_extension<'a, 'tcx>(this: &MoveData<'tcx>,
             }
         }
 
+        (&ty::TyUnion(..), None) => {
+            // Do nothing, all union fields are moved/assigned together.
+        }
+
         (&ty::TyEnum(def, _), ref enum_variant_info) => {
             let variant = match *enum_variant_info {
                 Some((vid, ref _lp2)) => def.variant_with_id(vid),

src/librustc_borrowck/borrowck/gather_loans/restrictions.rs

@@ -89,7 +89,7 @@ impl<'a, 'tcx> RestrictionsContext<'a, 'tcx> {
                 self.restrict(cmt_base)
             }
 
-            Categorization::Interior(cmt_base, i) => {
+            Categorization::Interior(cmt_base, interior) => {
                 // R-Field
                 //
                 // Overwriting the base would not change the type of
@@ -99,8 +99,34 @@ impl<'a, 'tcx> RestrictionsContext<'a, 'tcx> {
                     Categorization::Downcast(_, variant_id) => Some(variant_id),
                     _ => None
                 };
+                let interior = interior.cleaned();
+                let base_ty = cmt_base.ty;
                 let result = self.restrict(cmt_base);
-                self.extend(result, &cmt, LpInterior(opt_variant_id, i.cleaned()))
+                if let ty::TyUnion(ref adt_def, _) = base_ty.sty {
+                    match result {
+                        RestrictionResult::Safe => RestrictionResult::Safe,
+                        RestrictionResult::SafeIf(base_lp, mut base_vec) => {
+                            for field in &adt_def.struct_variant().fields {
+                                let field = InteriorKind::InteriorField(mc::NamedField(field.name));
+                                let field_ty = if field == interior {
+                                    cmt.ty
+                                } else {
+                                    self.bccx.tcx.types.err // Doesn't matter
+                                };
+                                let sibling_lp_kind = LpExtend(base_lp.clone(), cmt.mutbl,
+                                                               LpInterior(opt_variant_id, field));
+                                let sibling_lp = Rc::new(LoanPath::new(sibling_lp_kind, field_ty));
+                                base_vec.push(sibling_lp);
+                            }
+
+                            let lp = new_lp(LpExtend(base_lp, cmt.mutbl,
+                                                     LpInterior(opt_variant_id, interior)));
+                            RestrictionResult::SafeIf(lp, base_vec)
+                        }
+                    }
+                } else {
+                    self.extend(result, &cmt, LpInterior(opt_variant_id, interior))
+                }
             }
 
             Categorization::StaticItem => {

src/librustc_borrowck/borrowck/mod.rs

@@ -477,8 +477,6 @@ impl<'a, 'tcx> LoanPath<'tcx> {
                     base.common(&base2).map(|x| {
                         let xd = x.depth();
                         if base.depth() == xd && base2.depth() == xd {
-                            assert_eq!(base.ty, base2.ty);
-                            assert_eq!(self.ty, other.ty);
                             LoanPath {
                                 kind: LpExtend(Rc::new(x), a, LpInterior(opt_variant_id, id)),
                                 ty: self.ty,
@@ -495,15 +493,13 @@ impl<'a, 'tcx> LoanPath<'tcx> {
             (_, &LpExtend(ref other, _, LpDeref(_))) => self.common(&other),
             (&LpVar(id), &LpVar(id2)) => {
                 if id == id2 {
-                    assert_eq!(self.ty, other.ty);
                     Some(LoanPath { kind: LpVar(id), ty: self.ty })
                 } else {
                     None
                 }
             }
             (&LpUpvar(id), &LpUpvar(id2)) => {
                 if id == id2 {
-                    assert_eq!(self.ty, other.ty);
                     Some(LoanPath { kind: LpUpvar(id), ty: self.ty })
                 } else {
                     None
@@ -1136,7 +1132,6 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                 out.push(')');
             }
 
-
             LpExtend(ref lp_base, _, LpInterior(_, InteriorField(fname))) => {
                 self.append_autoderefd_loan_path_to_string(&lp_base, out);
                 match fname {

src/librustc_borrowck/borrowck/move_data.rs

@@ -21,7 +21,8 @@ use rustc::middle::dataflow::DataFlowOperator;
 use rustc::middle::dataflow::KillFrom;
 use rustc::middle::expr_use_visitor as euv;
 use rustc::middle::expr_use_visitor::MutateMode;
-use rustc::ty::TyCtxt;
+use rustc::middle::mem_categorization as mc;
+use rustc::ty::{self, TyCtxt};
 use rustc::util::nodemap::{FnvHashMap, NodeSet};
 
 use std::cell::RefCell;
@@ -364,6 +365,32 @@ impl<'a, 'tcx> MoveData<'tcx> {
                     lp: Rc<LoanPath<'tcx>>,
                     id: ast::NodeId,
                     kind: MoveKind) {
+        // Moving one union field automatically moves all its fields.
+        if let LpExtend(ref base_lp, mutbl, LpInterior(opt_variant_id, interior)) = lp.kind {
+            if let ty::TyUnion(ref adt_def, _) = base_lp.ty.sty {
+                for field in &adt_def.struct_variant().fields {
+                    let field = InteriorKind::InteriorField(mc::NamedField(field.name));
+                    let field_ty = if field == interior {
+                        lp.ty
+                    } else {
+                        tcx.types.err // Doesn't matter
+                    };
+                    let sibling_lp_kind = LpExtend(base_lp.clone(), mutbl,
+                                                   LpInterior(opt_variant_id, field));
+                    let sibling_lp = Rc::new(LoanPath::new(sibling_lp_kind, field_ty));
+                    self.add_move_helper(tcx, sibling_lp, id, kind);
+                }
+                return;
+            }
+        }
+
+        self.add_move_helper(tcx, lp.clone(), id, kind);
+    }
+
+    fn add_move_helper(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                       lp: Rc<LoanPath<'tcx>>,
+                       id: ast::NodeId,
+                       kind: MoveKind) {
         debug!("add_move(lp={:?}, id={}, kind={:?})",
                lp,
                id,
@@ -393,6 +420,34 @@ impl<'a, 'tcx> MoveData<'tcx> {
                           span: Span,
                           assignee_id: ast::NodeId,
                           mode: euv::MutateMode) {
+        // Assigning to one union field automatically assigns to all its fields.
+        if let LpExtend(ref base_lp, mutbl, LpInterior(opt_variant_id, interior)) = lp.kind {
+            if let ty::TyUnion(ref adt_def, _) = base_lp.ty.sty {
+                for field in &adt_def.struct_variant().fields {
+                    let field = InteriorKind::InteriorField(mc::NamedField(field.name));
+                    let field_ty = if field == interior {
+                        lp.ty
+                    } else {
+                        tcx.types.err // Doesn't matter
+                    };
+                    let sibling_lp_kind = LpExtend(base_lp.clone(), mutbl,
+                                                   LpInterior(opt_variant_id, field));
+                    let sibling_lp = Rc::new(LoanPath::new(sibling_lp_kind, field_ty));
+                    self.add_assignment_helper(tcx, sibling_lp, assign_id, span, assignee_id, mode);
+                }
+                return;
+            }
+        }
+
+        self.add_assignment_helper(tcx, lp.clone(), assign_id, span, assignee_id, mode);
+    }
+
+    pub fn add_assignment_helper(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                                 lp: Rc<LoanPath<'tcx>>,
+                                 assign_id: ast::NodeId,
+                                 span: Span,
+                                 assignee_id: ast::NodeId,
+                                 mode: euv::MutateMode) {
         debug!("add_assignment(lp={:?}, assign_id={}, assignee_id={}",
                lp, assign_id, assignee_id);
 

src/test/compile-fail/union-borrow-nested.rs

@@ -0,0 +1,44 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-tidy-linelength
+
+#![feature(untagged_unions)]
+
+#[derive(Clone, Copy)]
+struct S {
+    a: u8,
+    b: u16,
+}
+
+union U {
+    s: S,
+    c: u32,
+}
+
+impl Clone for U {
+    fn clone(&self) -> Self { *self }
+}
+impl Copy for U {}
+
+fn main() {
+    unsafe {
+        {
+            let mut u = U { s: S { a: 0, b: 1 } };
+            let ra = &mut u.s.a;
+            let b = u.s.b; // OK
+        }
+        {
+            let mut u = U { s: S { a: 0, b: 1 } };
+            let ra = &mut u.s.a;
+            let b = u.c; //~ ERROR cannot use `u.c` because it was mutably borrowed
+        }
+    }
+}

src/test/compile-fail/union-borrow.rs

@@ -0,0 +1,97 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-tidy-linelength
+
+#![feature(untagged_unions)]
+
+union U {
+    a: u8,
+    b: u64,
+}
+
+impl Clone for U {
+    fn clone(&self) -> Self { *self }
+}
+impl Copy for U {}
+
+fn main() {
+    unsafe {
+        let mut u = U { b: 0 };
+        // Imm borrow, same field
+        {
+            let ra = &u.a;
+            let ra2 = &u.a; // OK
+        }
+        {
+            let ra = &u.a;
+            let a = u.a; // OK
+        }
+        {
+            let ra = &u.a;
+            let rma = &mut u.a; //~ ERROR cannot borrow `u.a` as mutable because it is also borrowed as immutable
+        }
+        {
+            let ra = &u.a;
+            u.a = 1; //~ ERROR cannot assign to `u.a` because it is borrowed
+        }
+        // Imm borrow, other field
+        {
+            let ra = &u.a;
+            let rb = &u.b; // OK
+        }
+        {
+            let ra = &u.a;
+            let b = u.b; // OK
+        }
+        {
+            let ra = &u.a;
+            let rmb = &mut u.b; //~ ERROR cannot borrow `u` (via `u.b`) as mutable because `u` is also borrowed as immutable (via `u.a`)
+        }
+        {
+            let ra = &u.a;
+            u.b = 1; //~ ERROR cannot assign to `u.b` because it is borrowed
+        }
+        // Mut borrow, same field
+        {
+            let rma = &mut u.a;
+            let ra = &u.a; //~ ERROR cannot borrow `u.a` as immutable because it is also borrowed as mutable
+        }
+        {
+            let ra = &mut u.a;
+            let a = u.a; //~ ERROR cannot use `u.a` because it was mutably borrowed
+        }
+        {
+            let rma = &mut u.a;
+            let rma2 = &mut u.a; //~ ERROR cannot borrow `u.a` as mutable more than once at a time
+        }
+        {
+            let rma = &mut u.a;
+            u.a = 1; //~ ERROR cannot assign to `u.a` because it is borrowed
+        }
+        // Mut borrow, other field
+        {
+            let rma = &mut u.a;
+            let rb = &u.b; //~ ERROR cannot borrow `u` (via `u.b`) as immutable because `u` is also borrowed as mutable (via `u.a`)
+        }
+        {
+            let ra = &mut u.a;
+            let b = u.b; //~ ERROR cannot use `u.b` because it was mutably borrowed
+        }
+        {
+            let rma = &mut u.a;
+            let rmb2 = &mut u.b; //~ ERROR cannot borrow `u` (via `u.b`) as mutable more than once at a time
+        }
+        {
+            let rma = &mut u.a;
+            u.b = 1; //~ ERROR cannot assign to `u.b` because it is borrowed
+        }
+    }
+}

src/test/compile-fail/union-move-assign.rs

@@ -0,0 +1,42 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(untagged_unions)]
+
+// Non-copy
+struct A;
+struct B;
+
+union U {
+    a: A,
+    b: B,
+}
+
+fn main() {
+    unsafe {
+        {
+            let mut u = U { a: A };
+            let a = u.a;
+            let a = u.a; //~ ERROR use of moved value: `u.a`
+        }
+        {
+            let mut u = U { a: A };
+            let a = u.a;
+            u.a = A;
+            let a = u.a; // OK
+        }
+        {
+            let mut u = U { a: A };
+            let a = u.a;
+            u.b = B;
+            let a = u.a; // OK
+        }
+    }
+}