vala: Don't allow inheritance of compact class from non-compact class

tests/Makefile.am

@@ -1142,6 +1142,7 @@ TESTS = \
 	semantic/class-compact-field-lock.test \
 	semantic/class-compact-field-private.test \
 	semantic/class-compact-derived-instance-field.test \
+	semantic/class-compact-inheritance.test \
 	semantic/class-compact-interface.test \
 	semantic/class-compact-method-baseaccess.test \
 	semantic/class-compact-property-baseaccess.test \

tests/semantic/class-compact-inheritance.test

@@ -0,0 +1,11 @@
+Invalid Code
+
+class Foo {
+}
+
+[Compact]
+class Bar : Foo {
+}
+
+void main () {
+}

vala/valaclass.vala

@@ -606,6 +606,12 @@ public class Vala.Class : ObjectTypeSymbol {
 			}
 		}
 
+		if (base_class != null && !base_class.is_compact && has_attribute ("Compact")) {
+			error = true;
+			Report.error (source_reference, "Compact class `%s' cannot inherit from non-compact class `%s'", get_full_name (), base_class.get_full_name ());
+			return false;
+		}
+
 		/* process enums first to avoid order problems in C code */
 		foreach (Enum en in get_enums ()) {
 			en.check (context);