From f6753be655770cc6fd02db9e5c63131a4536f95e Mon Sep 17 00:00:00 2001
From: Marijn Haverbeke <marijnh@gmail.com>
Date: Sat, 25 Jun 2011 12:16:48 +0200
Subject: [PATCH] Allow moving out of temporary values

This will probably need more work, as moving doesn't appear to do
quite the right thing yet in general, and we should also check
somewhere that we're not, for example, moving out the content out of
an immutable field (probably moving out of fields is not okay in
general).
---
 src/comp/front/ast.rs                         |  7 +++++++
 src/comp/middle/tstate/pre_post_conditions.rs | 15 ++++++---------
 src/comp/middle/tstate/states.rs              |  9 +++------
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/src/comp/front/ast.rs b/src/comp/front/ast.rs
index bfe7d576cfd6..c601d7992148 100644
--- a/src/comp/front/ast.rs
+++ b/src/comp/front/ast.rs
@@ -301,6 +301,13 @@ tag lit_ {
     lit_bool(bool);
 }
 
+fn is_path(&@expr e) -> bool {
+    ret alt (e.node) {
+        case (expr_path(_)) { true }
+        case (_) { false }
+    };
+}
+
 
 // NB: If you change this, you'll probably want to change the corresponding
 // type structure in middle/ty.rs as well.
diff --git a/src/comp/middle/tstate/pre_post_conditions.rs b/src/comp/middle/tstate/pre_post_conditions.rs
index e5eaadbb2838..672894c06756 100644
--- a/src/comp/middle/tstate/pre_post_conditions.rs
+++ b/src/comp/middle/tstate/pre_post_conditions.rs
@@ -367,11 +367,12 @@ fn find_pre_post_expr(&fn_ctxt fcx, @expr e) {
                 }
                 case (_) { find_pre_post_exprs(fcx, [lhs, rhs], e.id); }
             }
-            forget_in_postcond(fcx, e.id, rhs.id);
+            if (is_path(rhs)) {
+                forget_in_postcond(fcx, e.id, rhs.id);
+            }
         }
         case (expr_swap(?lhs, ?rhs)) {
             // Both sides must already be initialized
-            
             find_pre_post_exprs(fcx, [lhs, rhs], e.id);
             forget_in_postcond_still_init(fcx, e.id, lhs.id);
             forget_in_postcond_still_init(fcx, e.id, rhs.id);
@@ -591,14 +592,10 @@ fn find_pre_post_stmt(&fn_ctxt fcx, &stmt s) {
                                 rec(id=alocal.node.id, 
                                     c=ninit(alocal.node.ident)));
                             
-                            alt (an_init.op) {
-                                case (init_move) {
-                                    forget_in_postcond(fcx, id,
-                                                       an_init.expr.id);
-                                }
-                                case (_) { /* nothing gets deinitialized */ } 
+                            if (an_init.op == init_move &&
+                                is_path(an_init.expr)) {
+                                forget_in_postcond(fcx, id, an_init.expr.id);
                             }
-
                         }
                         case (none) {
                             clear_pp(node_id_to_ts_ann(fcx.ccx,
diff --git a/src/comp/middle/tstate/states.rs b/src/comp/middle/tstate/states.rs
index 8af52ed83a04..386d1cff8a28 100644
--- a/src/comp/middle/tstate/states.rs
+++ b/src/comp/middle/tstate/states.rs
@@ -633,12 +633,9 @@ fn find_pre_post_state_stmt(&fn_ctxt fcx, &prestate pres, @stmt s) -> bool {
 
                             auto post = tritv_clone(expr_poststate(fcx.ccx,
                                                       an_init.expr));
-                            alt (an_init.op) {
-                                case (init_move) {
-                                    clear_in_poststate_expr(fcx, an_init.expr,
-                                                            post);
-                                }
-                                case (_) { /* nothing gets deinitialized */ } 
+                            if (an_init.op == init_move) {
+                                clear_in_poststate_expr(fcx, an_init.expr,
+                                                        post);
                             }
 
                             set_in_poststate_ident(fcx, alocal.node.id,