[vala/staging] vala: Check for matching ownership of type-arguments

[Rico Tzschichholz <ricotz src gnome org>]

commit 514fb744fb82828c9a5bd71ff80b7e41e3cfc34a
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Thu Apr 5 08:22:25 2018 +0200

    vala: Check for matching ownership of type-arguments
    
    Although don't complain (yet) if the target type is unowned.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=794979

 tests/Makefile.am             |    1 +
 tests/generics/bug794979.test |   11 +++++++++++
 vala/valadatatype.vala        |   16 +++++++++++++++-
 3 files changed, 27 insertions(+), 1 deletions(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 0645f2f..0d3544a 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -360,6 +360,7 @@ TESTS = \
        generics/bug694765-1.vala \
        generics/bug694765-2.vala \
        generics/bug694765-3.vala \
+       generics/bug794979.test \
        dbus/basic-types.test \
        dbus/arrays.test \
        dbus/structs.test \
diff --git a/tests/generics/bug794979.test b/tests/generics/bug794979.test
new file mode 100644
index 0000000..a4dd9cb
--- /dev/null
+++ b/tests/generics/bug794979.test
@@ -0,0 +1,11 @@
+Invalid Code
+
+class Foo<T> {
+}
+
+Foo<string> foo () {
+       return new Foo<unowned string> ();
+}
+
+void main () {
+}
diff --git a/vala/valadatatype.vala b/vala/valadatatype.vala
index 1bbbc82..208ffea 100644
--- a/vala/valadatatype.vala
+++ b/vala/valadatatype.vala
@@ -305,11 +305,25 @@ public abstract class Vala.DataType : CodeNode {
                        return true;
                }
 
+               // check for matching ownership of type-arguments
+               var type_args = get_type_arguments ();
+               var target_type_args = target_type.get_type_arguments ();
+               if (type_args.size == target_type_args.size) {
+                       for (int i = 0; i < type_args.size; i++) {
+                               // FIXME let it pass if the target "container" is unowned, but should there 
be a warning?
+                               // Ignore non-boxed simple-type structs
+                               if (!type_args[i].is_real_non_null_struct_type ()
+                                   && target_type.value_owned
+                                   && type_args[i].value_owned != target_type_args[i].value_owned) {
+                                       return false;
+                               }
+                       }
+               }
+
                if (data_type != null && target_type.data_type != null && data_type.is_subtype_of 
(target_type.data_type)) {
                        var base_type = SemanticAnalyzer.get_instance_base_type_for_member(this, 
target_type.data_type, this);
                        // check compatibility of generic type arguments
                        var base_type_args = base_type.get_type_arguments();
-                       var target_type_args = target_type.get_type_arguments();
                        if (base_type_args.size == target_type_args.size) {
                                for (int i = 0; i < base_type_args.size; i++) {
                                        // mutable generic types require type argument equality,