From 77c1b9650f055932bcad5983b9847517eba6c516 Mon Sep 17 00:00:00 2001
From: Marijn Haverbeke <marijnh@gmail.com>
Date: Thu, 9 Jun 2011 09:30:46 +0200
Subject: [PATCH] Some more workarounds to please the alias checker

Some of the vec utilities now only work on immutable vecs, since they
would have to be rewritten to do a lot more copying to be alias-safe.

Some forced copying was added to map.rs, showing a weakness in the
alias checker (or maybe the alias system): when fn args are passed
into a function, calling them must assume all aliases that are not
immutably rooted (directly connected to a local or temporary without
any mutable edges) become invalid. This will be a drag on functional
programming in Rust.

Work around alias issues in the stdlib
---
 src/comp/back/link.rs |  3 ++-
 src/lib/map.rs        | 18 ++++++++++++------
 src/lib/sort.rs       | 12 ++++++------
 src/lib/ufind.rs      |  2 +-
 src/lib/vec.rs        | 12 ++++++------
 5 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/src/comp/back/link.rs b/src/comp/back/link.rs
index b637b7e41b8..81c0f5a265a 100644
--- a/src/comp/back/link.rs
+++ b/src/comp/back/link.rs
@@ -339,7 +339,8 @@ fn crate_meta_extras_hash(sha1 sha, &ast::crate crate) -> str {
     }
     sort::quick_sort(lteq, v);
     sha.reset();
-    for (@ast::meta_item m in v) {
+    for (@ast::meta_item m_ in v) {
+        auto m = m_;
         sha.input_str(len_and_str(m.node.name));
         sha.input_str(len_and_str(m.node.value));
     }
diff --git a/src/lib/map.rs b/src/lib/map.rs
index 3b7f01acbe1..396835bc1d6 100644
--- a/src/lib/map.rs
+++ b/src/lib/map.rs
@@ -76,8 +76,10 @@ fn mk_hashmap[K, V](&hashfn[K] hasher, &eqfn[K] eqer) -> hashmap[K, V] {
                 let uint j = hash(h, nbkts, i);
                 alt (bkts.(j)) {
                     case (some(?k, _)) {
-                        if (eqer(key, k)) {
-                            bkts.(j) = some[K, V](k, val);
+                        // Copy key to please alias analysis.
+                        auto k_ = k;
+                        if (eqer(key, k_)) {
+                            bkts.(j) = some[K, V](k_, val);
                             ret false;
                         }
                         i += 1u;
@@ -104,8 +106,11 @@ fn mk_hashmap[K, V](&hashfn[K] hasher, &eqfn[K] eqer) -> hashmap[K, V] {
                 let uint j = (hash(h, nbkts, i));
                 alt (bkts.(j)) {
                     case (some(?k, ?v)) {
-                        if (eqer(key, k)) {
-                            ret option::some[V](v);
+                        // Copy to please alias analysis.
+                        auto k_ = k;
+                        auto v_ = v;
+                        if (eqer(key, k_)) {
+                            ret option::some[V](v_);
                         }
                     }
                     case (nil) {
@@ -190,10 +195,11 @@ fn mk_hashmap[K, V](&hashfn[K] hasher, &eqfn[K] eqer) -> hashmap[K, V] {
                     let uint j = (hash(h, nbkts, i));
                     alt (bkts.(j)) {
                         case (some(?k, ?v)) {
-                            if (eqer(key, k)) {
+                            auto k_ = k; auto vo = option::some(v);
+                            if (eqer(key, k_)) {
                                 bkts.(j) = deleted[K, V];
                                 nelts -= 1u;
-                                ret option::some[V](v);
+                                ret vo;
                             }
                         }
                         case (deleted) { }
diff --git a/src/lib/sort.rs b/src/lib/sort.rs
index ede8d229fa5..8a16c1858be 100644
--- a/src/lib/sort.rs
+++ b/src/lib/sort.rs
@@ -58,7 +58,7 @@ fn part[T](lteq[T] compare_func, vec[mutable T] arr, uint left,
     let uint storage_index = left;
     let uint i = left;
     while (i<right) {
-        if (compare_func(arr.(i), pivot_value)) {
+        if (compare_func({arr.(i)}, pivot_value)) {
            swap[T](arr, i, storage_index);
            storage_index += 1u;
         }
@@ -97,7 +97,7 @@ fn quick_sort[T](lteq[T] compare_func, vec[mutable T] arr) {
 // 'randomly ordered keys, abstract compare' & 'small number of key values'
 
 fn qsort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
-        vec[mutable T] arr, int left, int right) {
+             vec[mutable T] arr, int left, int right) {
 
     if (right <= left) {
         ret;
@@ -111,11 +111,11 @@ fn qsort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
 
     while (true) {
         i += 1;
-        while (compare_func_lt(arr.(i), v)) {
+        while (compare_func_lt({arr.(i)}, v)) {
             i += 1;
         }
         j -= 1;
-        while (compare_func_lt(v, arr.(j))) {
+        while (compare_func_lt(v, {arr.(j)})) {
             if (j == left) {
                 break;
             }
@@ -125,11 +125,11 @@ fn qsort3[T](lteq[T] compare_func_lt, lteq[T] compare_func_eq,
             break;
         }
         swap[T](arr, i as uint, j as uint);
-        if (compare_func_eq(arr.(i), v)) {
+        if (compare_func_eq({arr.(i)}, v)) {
             p += 1;
             swap[T](arr, p as uint, i as uint);
         }
-        if (compare_func_eq(v, arr.(j))) {
+        if (compare_func_eq(v, {arr.(j)})) {
             q -= 1;
             swap[T](arr, j as uint, q as uint);
         }
diff --git a/src/lib/ufind.rs b/src/lib/ufind.rs
index 275efd813e4..2d81be65e2e 100644
--- a/src/lib/ufind.rs
+++ b/src/lib/ufind.rs
@@ -29,7 +29,7 @@ fn grow(&ufind ufnd, uint n) {
 fn find(&ufind ufnd, uint n) -> uint {
     alt (ufnd.nodes.(n)) {
         case (none) { ret n; }
-        case (some(?m)) { be find(ufnd, m); }
+        case (some(?m)) { auto m_ = m; be find(ufnd, m_); }
     }
 }
 
diff --git a/src/lib/vec.rs b/src/lib/vec.rs
index 2f82f330446..3cc4db83b54 100644
--- a/src/lib/vec.rs
+++ b/src/lib/vec.rs
@@ -241,7 +241,7 @@ fn grow_init_fn_set[T](&array[T] v, uint index, fn()->T init_fn, &T val) {
 }
 
 
-fn map[T, U](&fn(&T) -> U f, &array[T] v) -> vec[U] {
+fn map[T, U](&fn(&T) -> U f, &vec[T] v) -> vec[U] {
     let vec[U] res = alloc[U](len[T](v));
     for (T ve in v) {
         res += [f(ve)];
@@ -249,8 +249,8 @@ fn map[T, U](&fn(&T) -> U f, &array[T] v) -> vec[U] {
     ret res;
 }
 
-fn filter_map[T, U](&fn(&T) -> option::t[U] f, &array[T] v) -> vec[U] {
-    let vec[U] res = []; //TODO does this work these days?
+fn filter_map[T, U](&fn(&T) -> option::t[U] f, &vec[T] v) -> vec[U] {
+    let vec[U] res = [];
     for(T ve in v) {
         alt(f(ve)) {
             case (some(?elt)) { res += [elt]; }
@@ -260,7 +260,7 @@ fn filter_map[T, U](&fn(&T) -> option::t[U] f, &array[T] v) -> vec[U] {
     ret res;
 }
 
-fn map2[T,U,V](&operator2[T,U,V] f, &array[T] v0, &array[U] v1) -> vec[V] {
+fn map2[T,U,V](&operator2[T,U,V] f, &vec[T] v0, &vec[U] v1) -> vec[V] {
     auto v0_len = len[T](v0);
     if (v0_len != len[U](v1)) {
         fail;
@@ -269,14 +269,14 @@ fn map2[T,U,V](&operator2[T,U,V] f, &array[T] v0, &array[U] v1) -> vec[V] {
     let vec[V] u = alloc[V](v0_len);
     auto i = 0u;
     while (i < v0_len) {
-        u += [f(v0.(i), v1.(i))];
+        u += [f({v0.(i)}, {v1.(i)})];
         i += 1u;
     }
 
     ret u;
 }
 
-fn find[T](fn (&T) -> bool f, &array[T] v) -> option::t[T] {
+fn find[T](fn (&T) -> bool f, &vec[T] v) -> option::t[T] {
     for (T elt in v) {
         if (f(elt)) {
             ret some[T](elt);