From 29003c799f41cce948bc043cdd1350ca4bee949e Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Mon, 10 Sep 2012 16:34:31 -0700
Subject: [PATCH] Rename the poorly named Managed<T> type to Mut<T>.

The Mut<T> type is intended to allow freezable data stuctures to be stored in
`@mut` boxes. Currently this causes borrowck to be very conserivative since it
cannot prove that you are not modifying such a structure while iterating over
it, for example.  But if you do `@Mut<T>` instead of `@mut T`, you will
effectively convert borrowck's static checks into dynamic ones.  This lets
you use the e.g. send_map just like a Java Map or something else.
---
 src/libcore/core.rc                    |  4 +--
 src/libcore/{managed.rs => mutable.rs} | 36 ++++++++++++++++----------
 src/libstd/map.rs                      |  4 +--
 src/test/bench/core-map.rs             | 10 +++----
 4 files changed, 31 insertions(+), 23 deletions(-)
 rename src/libcore/{managed.rs => mutable.rs} (78%)

diff --git a/src/libcore/core.rc b/src/libcore/core.rc
index 25bdcea0bb2..c0c9cf5f9b6 100644
--- a/src/libcore/core.rc
+++ b/src/libcore/core.rc
@@ -57,7 +57,7 @@ export hash;
 export cmp;
 export num;
 export path;
-export managed;
+export mutable;
 export flate;
 export unit;
 export uniq;
@@ -225,7 +225,7 @@ mod run;
 mod sys;
 mod unsafe;
 
-mod managed;
+mod mutable;
 
 mod flate;
 
diff --git a/src/libcore/managed.rs b/src/libcore/mutable.rs
similarity index 78%
rename from src/libcore/managed.rs
rename to src/libcore/mutable.rs
index b3119b9d24d..eca9ff6fada 100644
--- a/src/libcore/managed.rs
+++ b/src/libcore/mutable.rs
@@ -15,7 +15,7 @@ mutation when the data structure should be immutable.
 use util::with;
 use unsafe::transmute_immut;
 
-export Managed;
+export Mut;
 
 enum Mode { ReadOnly, Mutable, Immutable }
 
@@ -24,18 +24,26 @@ struct Data<T> {
     priv mut mode: Mode
 }
 
-type Managed<T> = @Data<T>;
+type Mut<T> = Data<T>;
 
-fn Managed<T>(+t: T) -> Managed<T> {
-    @Data {value: t, mode: ReadOnly}
+fn Mut<T>(+t: T) -> Mut<T> {
+    Data {value: t, mode: ReadOnly}
+}
+
+fn unwrap<T>(+m: Mut<T>) -> T {
+    // Borrowck should prevent us from calling unwrap while the value
+    // is in use, as that would be a move from a borrowed value.
+    assert (m.mode as uint) == (ReadOnly as uint);
+    let Data {value, mode: _} = m;
+    return move value;
 }
 
 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 => {}
+            Immutable => fail fmt!("%? currently immutable",
+                                   self.value),
+            ReadOnly | Mutable => {}
         }
 
         do with(&mut self.mode, Mutable) {
@@ -64,7 +72,7 @@ impl<T> Data<T> {
 #[ignore(cfg(windows))]
 #[should_fail]
 fn test_mut_in_imm() {
-    let m = Managed(1);
+    let m = @Mut(1);
     do m.borrow_imm |_p| {
         do m.borrow_mut |_q| {
             // should not be permitted
@@ -76,7 +84,7 @@ fn test_mut_in_imm() {
 #[ignore(cfg(windows))]
 #[should_fail]
 fn test_imm_in_mut() {
-    let m = Managed(1);
+    let m = @Mut(1);
     do m.borrow_mut |_p| {
         do m.borrow_imm |_q| {
             // should not be permitted
@@ -86,7 +94,7 @@ fn test_imm_in_mut() {
 
 #[test]
 fn test_const_in_mut() {
-    let m = Managed(1);
+    let m = @Mut(1);
     do m.borrow_mut |p| {
         do m.borrow_const |q| {
             assert *p == *q;
@@ -98,7 +106,7 @@ fn test_const_in_mut() {
 
 #[test]
 fn test_mut_in_const() {
-    let m = Managed(1);
+    let m = @Mut(1);
     do m.borrow_const |p| {
         do m.borrow_mut |q| {
             assert *p == *q;
@@ -110,7 +118,7 @@ fn test_mut_in_const() {
 
 #[test]
 fn test_imm_in_const() {
-    let m = Managed(1);
+    let m = @Mut(1);
     do m.borrow_const |p| {
         do m.borrow_imm |q| {
             assert *p == *q;
@@ -120,7 +128,7 @@ fn test_imm_in_const() {
 
 #[test]
 fn test_const_in_imm() {
-    let m = Managed(1);
+    let m = @Mut(1);
     do m.borrow_imm |p| {
         do m.borrow_const |q| {
             assert *p == *q;
@@ -133,7 +141,7 @@ fn test_const_in_imm() {
 #[ignore(cfg(windows))]
 #[should_fail]
 fn test_mut_in_imm_in_const() {
-    let m = Managed(1);
+    let m = @Mut(1);
     do m.borrow_const |_p| {
         do m.borrow_imm |_q| {
             do m.borrow_mut |_r| {
diff --git a/src/libstd/map.rs b/src/libstd/map.rs
index 5436ea1a803..cd19da61ab6 100644
--- a/src/libstd/map.rs
+++ b/src/libstd/map.rs
@@ -5,7 +5,7 @@
 
 use io::WriterUtil;
 use to_str::ToStr;
-use managed::Managed;
+use mutable::Mut;
 use send_map::linear::LinearMap;
 
 use core::cmp::Eq;
@@ -463,7 +463,7 @@ fn hash_from_uints<V: Copy>(items: &[(uint, V)]) -> hashmap<uint, V> {
 }
 
 // XXX Transitional
-impl<K: Eq IterBytes Hash Copy, V: Copy> Managed<LinearMap<K, V>>:
+impl<K: Eq IterBytes Hash Copy, V: Copy> @Mut<LinearMap<K, V>>:
     map<K, V> {
     pure fn size() -> uint {
         unchecked {
diff --git a/src/test/bench/core-map.rs b/src/test/bench/core-map.rs
index 4901a85369a..112c25d5146 100644
--- a/src/test/bench/core-map.rs
+++ b/src/test/bench/core-map.rs
@@ -6,7 +6,7 @@
 
 use std;
 use std::map;
-use managed::Managed;
+use mutable::Mut;
 use send_map::linear::*;
 use io::WriterUtil;
 
@@ -166,11 +166,11 @@ fn main(args: ~[~str]) {
     {
         let rng = rand::seeded_rng(copy seed);
         let mut results = empty_results();
-        int_benchmarks::<Managed<LinearMap<uint, uint>>>(
-            || Managed(LinearMap()),
+        int_benchmarks::<@Mut<LinearMap<uint, uint>>>(
+            || @Mut(LinearMap()),
             rng, num_keys, &mut results);
-        str_benchmarks::<Managed<LinearMap<~str, uint>>>(
-            || Managed(LinearMap()),
+        str_benchmarks::<@Mut<LinearMap<~str, uint>>>(
+            || @Mut(LinearMap()),
             rng, num_keys, &mut results);
         write_results("libstd::map::hashmap", &results);
     }