[vala] codegen: Destroy value of "as" cast in case the result is null

[Luca Bruno <lucabru src gnome org>]

commit fd55b251c171d89bb5754b601f4a99981d0b3916
Author: Luca Bruno <lucabru src gnome org>
Date:   Wed Mar 20 23:32:19 2013 +0000

    codegen: Destroy value of "as" cast in case the result is null
    
    Fixes bug 695671.

 codegen/valaccodebasemodule.vala |   26 +++++++++++++++++++++-----
 tests/Makefile.am                |    1 +
 tests/objects/bug695671.vala     |   37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 5 deletions(-)
---
diff --git a/codegen/valaccodebasemodule.vala b/codegen/valaccodebasemodule.vala
index 93d04ee..a8d9e8c 100644
--- a/codegen/valaccodebasemodule.vala
+++ b/codegen/valaccodebasemodule.vala
@@ -3200,8 +3200,6 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                return destroy_value (get_field_cvalue (field, instance));
        }
 
-       // logic in this method is temporarily duplicated in destroy_variable
-       // apply changes to both methods
        public virtual CCodeExpression destroy_value (TargetValue value, bool is_macro_definition = false) {
                var type = value.value_type;
                if (value.actual_value_type != null) {
@@ -3757,6 +3755,7 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                                    (st == null || get_ccode_name (st) != "va_list")) {
                                        // GArray and va_list don't use pointer-based generics
                                        set_cvalue (expr, convert_from_generic_pointer (get_cvalue (expr), 
expr.value_type));
+                                       ((GLibValue) expr.target_value).lvalue = false;
                                }
                        }
 
@@ -3775,6 +3774,7 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                                if (expr.formal_target_type.type_parameter.parent_symbol != garray_type) {
                                        // GArray doesn't use pointer-based generics
                                        set_cvalue (expr, convert_to_generic_pointer (get_cvalue (expr), 
expr.target_type));
+                                       ((GLibValue) expr.target_value).lvalue = false;
                                }
                        }
 
@@ -5015,12 +5015,25 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
                if (iface != null || (cl != null && !cl.is_compact)) {
                        // checked cast for strict subtypes of GTypeInstance
                        if (expr.is_silent_cast) {
-                               var cexpr = get_cvalue (expr.inner);
+                               TargetValue to_cast = expr.inner.target_value;
+                               CCodeExpression cexpr;
+                               if (!get_lvalue (to_cast)) {
+                                       to_cast = store_temp_value (to_cast, expr);
+                               }
+                               cexpr = get_cvalue_ (to_cast);
                                var ccheck = create_type_check (cexpr, expr.type_reference);
                                var ccast = new CCodeCastExpression (cexpr, get_ccode_name 
(expr.type_reference));
                                var cnull = new CCodeConstant ("NULL");
-
-                               set_cvalue (expr, new CCodeConditionalExpression (ccheck, ccast, cnull));
+                               var cast_value = new GLibValue (expr.value_type, new 
CCodeConditionalExpression (ccheck, ccast, cnull));
+                               if (requires_destroy (expr.inner.value_type)) {
+                                       var casted = store_temp_value (cast_value, expr);
+                                       ccode.open_if (new CCodeBinaryExpression 
(CCodeBinaryOperator.EQUALITY, get_cvalue_ (casted), new CCodeConstant ("NULL")));
+                                       ccode.add_expression (destroy_value (to_cast));
+                                       ccode.close ();
+                                       expr.target_value = ((GLibValue) casted).copy ();
+                               } else {
+                                       expr.target_value = cast_value;
+                               }
                        } else {
                                set_cvalue (expr, generate_instance_cast (get_cvalue (expr.inner), 
expr.type_reference.data_type));
                        }
@@ -5632,7 +5645,10 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
 
                        result.cvalue = new CCodeUnaryExpression (CCodeUnaryOperator.POINTER_INDIRECTION, 
result.cvalue);
                } else {
+                       // TODO: rewrite get_implicit_cast_expression to return a GLibValue
+                       var old_cexpr = result.cvalue;
                        result.cvalue = get_implicit_cast_expression (result.cvalue, type, target_type, node);
+                       result.lvalue = result.lvalue && result.cvalue == old_cexpr;
                }
 
                if (requires_temp_value && !(target_type is ArrayType && ((ArrayType) 
target_type).inline_allocated)) {
diff --git a/tests/Makefile.am b/tests/Makefile.am
index eedf8ce..c11565c 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -131,6 +131,7 @@ TESTS = \
        objects/bug664529.vala \
        objects/bug667668.vala \
        objects/bug683646.vala \
+       objects/bug695671.vala \
        errors/errors.vala \
        errors/bug567181.vala \
        errors/bug579101.vala \
diff --git a/tests/objects/bug695671.vala b/tests/objects/bug695671.vala
new file mode 100644
index 0000000..fb06be9
--- /dev/null
+++ b/tests/objects/bug695671.vala
@@ -0,0 +1,37 @@
+class Foo : Object {
+}
+
+G ref_generic<G> (G o) {
+       return o;
+}
+
+Object ref (Object o) {
+       return o;
+}
+
+void main () {
+       var o = new Object();
+       var f = (ref (o)) as Foo;
+       assert (f == null);
+       assert (o.ref_count == 1);
+
+       var g = (ref_generic (o)) as Foo;
+       assert (g == null);
+       assert (o.ref_count == 1);
+
+       var r = ref_generic (o) as Object;
+       assert (r == o);
+       assert (o.ref_count == 2);
+
+       var r2 = o as Object;
+       assert (r2 == o);
+       assert (o.ref_count == 3);
+
+       unowned Object r3 = o as Object;
+       assert (r3 == o);
+       assert (o.ref_count == 3);
+
+       unowned Object r4 = o as Foo;
+       assert (r4 == null);
+       assert (o.ref_count == 3);
+}