Reborrow even when passing &Object to &Object, so as to permit freezing

Author: nikomatsakis

src/librustc/middle/typeck/check/regionck.rs

@@ -391,7 +391,7 @@ fn visit_expr(expr: @ast::expr, (rcx, v): (@mut Rcx, rvt)) {
             let target_ty = rcx.resolve_node_type(expr.id);
             match ty::get(target_ty).sty {
                 ty::ty_trait(_, _, ty::RegionTraitStore(trait_region), _, _) => {
-                    let source_ty = rcx.fcx.expr_ty(source);
+                    let source_ty = rcx.resolve_expr_type_adjusted(source);
                     constrain_regions_in_type(
                         rcx,
                         trait_region,
@@ -1153,17 +1153,20 @@ pub mod guarantor {
         match ty::get(ty).sty {
             ty::ty_rptr(r, _) |
             ty::ty_evec(_, ty::vstore_slice(r)) |
+            ty::ty_trait(_, _, ty::RegionTraitStore(r), _, _) |
             ty::ty_estr(ty::vstore_slice(r)) => {
                 BorrowedPointer(r)
             }
             ty::ty_uniq(*) |
             ty::ty_estr(ty::vstore_uniq) |
+            ty::ty_trait(_, _, ty::UniqTraitStore, _, _) |
             ty::ty_evec(_, ty::vstore_uniq) => {
                 OwnedPointer
             }
             ty::ty_box(*) |
             ty::ty_ptr(*) |
             ty::ty_evec(_, ty::vstore_box) |
+            ty::ty_trait(_, _, ty::BoxTraitStore, _, _) |
             ty::ty_estr(ty::vstore_box) => {
                 OtherPointer
             }

src/librustc/middle/typeck/infer/coercion.rs

@@ -285,9 +285,6 @@ impl Coerce {
         let r_a = self.infcx.next_region_var(Coercion(self.trace));
 
         let a_borrowed = match *sty_a {
-            ty::ty_trait(_, _, ty::RegionTraitStore(_), _, _) => {
-                return self.subtype(a, b);
-            }
             ty::ty_trait(did, ref substs, _, _, b) => {
                 ty::mk_trait(tcx, did, substs.clone(),
                              ty::RegionTraitStore(r_a), b_mutbl, b)
@@ -297,7 +294,7 @@ impl Coerce {
             }
         };
 
-        if_ok!(self.tys(a_borrowed, b));
+        if_ok!(self.subtype(a_borrowed, b));
         Ok(Some(@AutoDerefRef(AutoDerefRef {
             autoderefs: 0,
             autoref: Some(AutoBorrowObj(r_a, b_mutbl))

src/test/run-pass/objects-coerce-freeze-borrored.rs

@@ -0,0 +1,48 @@
+// Copyright 2012 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.
+
+// Test that we can coerce an `@Object` to an `&Object`
+
+trait Foo {
+    fn foo(&self) -> uint;
+    fn bar(&mut self) -> uint;
+}
+
+impl Foo for uint {
+    fn foo(&self) -> uint {
+        *self
+    }
+
+    fn bar(&mut self) -> uint {
+        *self += 1;
+        *self
+    }
+}
+
+fn do_it_mut(obj: &mut Foo) {
+    let x = obj.bar();
+    let y = obj.foo();
+    assert_eq!(x, y);
+
+    do_it_imm(obj, y);
+}
+
+fn do_it_imm(obj: &Foo, v: uint) {
+    let y = obj.foo();
+    assert_eq!(v, y);
+}
+
+fn main() {
+    let mut x = 22_u;
+    let obj = &mut x as &mut Foo;
+    do_it_mut(obj);
+    do_it_imm(obj, 23u);
+    do_it_mut(obj);
+}