[vala/0.40] vala: Restore DestroysInstance behaviour for non-compact classes

[Rico Tzschichholz <ricotz src gnome org>]

commit 06cf307ddafbed9d204919e18e6119be94a20007
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Wed Nov 6 21:03:51 2019 +0100

    vala: Restore DestroysInstance behaviour for non-compact classes
    
    Although this attribute is not meant to be applied on methods of reference
    counted classes, the original behaviour should not be changed silently.
    
    Regression of 3d83f31a659bd179e8a867dd054126ac6f22e82b
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/873

 tests/Makefile.am                         |  1 +
 tests/objects/class-destroysinstance.vala | 15 +++++++++++++++
 vala/valamemberaccess.vala                |  3 ++-
 3 files changed, 18 insertions(+), 1 deletion(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 13bf49e3e..87657cba3 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -276,6 +276,7 @@ TESTS = \
        delegates/bug772204.test \
        delegates/bug792077.vala \
        objects/chainup.vala \
+       objects/class-destroysinstance.vala \
        objects/classes.vala \
        objects/compact-class-destructor.vala \
        objects/constructor-variadic.test \
diff --git a/tests/objects/class-destroysinstance.vala b/tests/objects/class-destroysinstance.vala
new file mode 100644
index 000000000..d5de16b62
--- /dev/null
+++ b/tests/objects/class-destroysinstance.vala
@@ -0,0 +1,15 @@
+class Foo : Object {
+       [DestroysInstance]
+       public void free () {
+               assert (this.ref_count == 2);
+               this.unref ();
+       }
+}
+
+void main () {
+       var foo = new Foo ();
+       {
+               foo.free ();
+       }
+       assert (foo.ref_count == 1);
+}
diff --git a/vala/valamemberaccess.vala b/vala/valamemberaccess.vala
index 94da85103..91c8303b8 100644
--- a/vala/valamemberaccess.vala
+++ b/vala/valamemberaccess.vala
@@ -915,7 +915,8 @@ public class Vala.MemberAccess : Expression {
                }
 
                if (symbol_reference is Method && ((Method) symbol_reference).get_attribute 
("DestroysInstance") != null) {
-                       if (ma != null) {
+                       unowned Class? cl = ((Method) symbol_reference).parent_symbol as Class;
+                       if (cl != null && cl.is_compact && ma != null) {
                                ma.lvalue = true;
                                ma.check_lvalue_access ();
                        }