[vala] Fix semantics for coalesce operator when target_type is null.

[Luca Bruno <lucabru src gnome org>]

commit 6949360735ce69776f3e64d25fc3efab5ce387e5
Author: Luca Bruno <lucabru src gnome org>
Date:   Sun Jan 26 12:10:57 2014 +0100

    Fix semantics for coalesce operator when target_type is null.
    
    Fixes bug 639482

 tests/Makefile.am                 |    1 +
 tests/control-flow/bug639482.vala |    4 ++++
 vala/valabinaryexpression.vala    |   14 +++++++++++---
 3 files changed, 16 insertions(+), 3 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 85a9213..5d89abf 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -63,6 +63,7 @@ TESTS = \
        control-flow/foreach.vala \
        control-flow/switch.vala \
        control-flow/sideeffects.vala \
+       control-flow/bug639482.vala \
        control-flow/bug652549.vala \
        control-flow/bug665904.vala \
        control-flow/bug691514.vala     \
diff --git a/tests/control-flow/bug639482.vala b/tests/control-flow/bug639482.vala
new file mode 100644
index 0000000..27a8e20
--- /dev/null
+++ b/tests/control-flow/bug639482.vala
@@ -0,0 +1,4 @@
+void main () {
+       string empty = null;
+       assert ((false ? "A" : (empty ?? "B")) == "B");
+}
diff --git a/vala/valabinaryexpression.vala b/vala/valabinaryexpression.vala
index 2b7289c..19766e1 100644
--- a/vala/valabinaryexpression.vala
+++ b/vala/valabinaryexpression.vala
@@ -221,10 +221,18 @@ public class Vala.BinaryExpression : Expression {
                        }
 
                        var ma = new MemberAccess.simple (local.name, source_reference);
-                       ma.target_type = target_type;
-                       ma.check (context);
+                       Expression replace = ma;
 
-                       parent_node.replace_expression (this, ma);
+                       if (target_type == null) {
+                               replace = new ReferenceTransferExpression (replace, source_reference);
+                               replace.target_type = local.variable_type.copy ();
+                               replace.target_type.value_owned = true;
+                       } else {
+                               replace.target_type = target_type.copy ();
+                       }
+                       replace.check (context);
+
+                       parent_node.replace_expression (this, replace);
 
                        return true;
                }