Issue #9629 -- permit freezing &mut found within an & pointer

src/test/compile-fail/borrowck-borrow-of-mut-base-ptr.rs

@@ -0,0 +1,27 @@
+// Copyright 2013 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 attempt to freeze an `&mut` pointer while referent is
+// claimed yields an error.
+//
+// Example from src/middle/borrowck/doc.rs
+
+use std::util::swap;
+
+fn foo<'a>(mut t0: &'a mut int,
+           mut t1: &'a mut int) {
+    let p: &mut int = &mut *t0; // Claims `*t0`
+    let mut t2 = &t0;           //~ ERROR cannot borrow `t0`
+    let q: &int = &*t2;         // Freezes `*t0` but not through `*p`
+    *p += 1;                    // violates type of `*q`
+}
+
+fn main() {
+}

src/test/compile-fail/borrowck-mut-borrow-of-mut-base-ptr.rs

@@ -0,0 +1,33 @@
+// Copyright 2013 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 attempt to mutably borrow `&mut` pointer while pointee is
+// borrowed yields an error.
+//
+// Example from src/middle/borrowck/doc.rs
+
+use std::util::swap;
+
+fn foo<'a>(mut t0: &'a mut int,
+           mut t1: &'a mut int) {
+    let p: &int = &*t0;     // Freezes `*t0`
+    let mut t2 = &mut t0;   //~ ERROR cannot borrow `t0`
+    **t2 += 1;              // Mutates `*t0`
+}
+
+fn bar<'a>(mut t0: &'a mut int,
+           mut t1: &'a mut int) {
+    let p: &mut int = &mut *t0; // Claims `*t0`
+    let mut t2 = &mut t0;       //~ ERROR cannot borrow `t0`
+    **t2 += 1;                  // Mutates `*t0` but not through `*p`
+}
+
+fn main() {
+}

src/test/run-pass/borrowck-borrow-of-mut-base-ptr-safe.rs

@@ -0,0 +1,25 @@
+// Copyright 2013 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 freezing an `&mut` pointer while referent is
+// frozen is legal.
+//
+// Example from src/middle/borrowck/doc.rs
+
+fn foo<'a>(mut t0: &'a mut int,
+           mut t1: &'a mut int) {
+    let p: &int = &*t0; // Freezes `*t0`
+    let mut t2 = &t0;
+    let q: &int = &**t2; // Freezes `*t0`, but that's ok...
+    let r: &int = &*t0; // ...after all, could do same thing directly.
+}
+
+fn main() {
+}

src/test/run-pass/borrowck-freeze-frozen-mut.rs

@@ -0,0 +1,36 @@
+// Copyright 2012-2013 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 a `&mut` inside of an `&` is freezable.
+
+struct MutSlice<'a, T> {
+    data: &'a mut [T]
+}
+
+fn get<'a, T>(ms: &'a MutSlice<'a, T>, index: uint) -> &'a T {
+    &ms.data[index]
+}
+
+fn main() {
+    let mut data = [1, 2, 3];
+    {
+        let slice = MutSlice { data: data };
+        slice.data[0] += 4;
+        let index0 = get(&slice, 0);
+        let index1 = get(&slice, 1);
+        let index2 = get(&slice, 2);
+        assert_eq!(*index0, 5);
+        assert_eq!(*index1, 2);
+        assert_eq!(*index2, 3);
+    }
+    assert_eq!(data[0], 1);
+    assert_eq!(data[1], 2);
+    assert_eq!(data[2], 3);
+}