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/*!
Module for wrapping freezable data structures in managed boxes.
Normally freezable data structures require an unaliased reference,
such as `T` or `~T`, so that the compiler can track when they are
being mutated. The `managed<T>` type converts these static checks into
dynamic checks: your program will fail if you attempt to perform
mutation when the data structure should be immutable.
*/
#[forbid(non_camel_case_types)];
#[forbid(deprecated_mode)];
#[forbid(deprecated_pattern)];
import util::with;
import unsafe::transmute_immut;
export Managed;
enum Mode { ReadOnly, Mutable, Immutable }
struct Data<T> {
priv mut value: T;
priv mut mode: Mode;
}
type Managed<T> = @Data<T>;
fn Managed<T>(+t: T) -> Managed<T> {
@Data {value: t, mode: ReadOnly}
}
impl<T> Data<T> {
fn borrow_mut<R>(op: &fn(t: &mut T) -> R) -> R {
match self.mode {
Immutable => fail fmt!("%? currently immutable",
self.value),
ReadOnly | Mutable => {}
}
do with(&mut self.mode, Mutable) {
op(&mut self.value)
}
}
fn borrow_const<R>(op: &fn(t: &const T) -> R) -> R {
op(&const self.value)
}
fn borrow_imm<R>(op: &fn(t: &T) -> R) -> R {
match self.mode {
Mutable => fail fmt!("%? currently mutable",
self.value),
ReadOnly | Immutable => {}
}
do with(&mut self.mode, Immutable) {
op(unsafe{transmute_immut(&mut self.value)})
}
}
}
#[test]
#[ignore(cfg(windows))]
#[should_fail]
fn test_mut_in_imm() {
let m = Managed(1);
do m.borrow_imm |_p| {
do m.borrow_mut |_q| {
// should not be permitted
}
}
}
#[test]
#[ignore(cfg(windows))]
#[should_fail]
fn test_imm_in_mut() {
let m = Managed(1);
do m.borrow_mut |_p| {
do m.borrow_imm |_q| {
// should not be permitted
}
}
}
#[test]
fn test_const_in_mut() {
let m = Managed(1);
do m.borrow_mut |p| {
do m.borrow_const |q| {
assert *p == *q;
*p += 1;
assert *p == *q;
}
}
}
#[test]
fn test_mut_in_const() {
let m = Managed(1);
do m.borrow_const |p| {
do m.borrow_mut |q| {
assert *p == *q;
*q += 1;
assert *p == *q;
}
}
}
#[test]
fn test_imm_in_const() {
let m = Managed(1);
do m.borrow_const |p| {
do m.borrow_imm |q| {
assert *p == *q;
}
}
}
#[test]
fn test_const_in_imm() {
let m = Managed(1);
do m.borrow_imm |p| {
do m.borrow_const |q| {
assert *p == *q;
}
}
}
#[test]
#[ignore(cfg(windows))]
#[should_fail]
fn test_mut_in_imm_in_const() {
let m = Managed(1);
do m.borrow_const |_p| {
do m.borrow_imm |_q| {
do m.borrow_mut |_r| {
}
}
}
}
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