[vala/wip/type-arg-mismatch: 4/4] vala: Check for matching ownership of type-arguments

[Rico Tzschichholz <ricotz src gnome org>]

commit 4f5a770f20c0d13a0bee6e02af20a458aa378b1c
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Thu Apr 5 08:22:25 2018 +0200

    vala: Check for matching ownership of type-arguments
    
    Non-boxed simple types can't be unowned and are therefore ignored.
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/696

 tests/Makefile.am                                  |  1 +
 .../semantic/type-argument-ownership-mismatch.test | 11 ++++++++++
 vala/valadatatype.vala                             | 24 +++++++++++++++++++++-
 3 files changed, 35 insertions(+), 1 deletion(-)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index fd0d24675..800284942 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -619,6 +619,7 @@ TESTS = \
        semantic/struct-field-initializer.test \
        semantic/struct-invalid-base.test \
        semantic/struct-recursive.test \
+       semantic/type-argument-ownership-mismatch.test \
        semantic/yield-call-requires-async-context.test \
        semantic/yield-call-requires-async-method.test \
        semantic/yield-creation-requires-async-context.test \
diff --git a/tests/semantic/type-argument-ownership-mismatch.test 
b/tests/semantic/type-argument-ownership-mismatch.test
new file mode 100644
index 000000000..a4dd9cb7e
--- /dev/null
+++ b/tests/semantic/type-argument-ownership-mismatch.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 8c52a4bfa..1e2f2c4cf 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++) {
+                               var type_arg = type_args[i];
+                               var target_type_arg = target_type_args[i];
+                               // Ignore non-boxed simple-type structs
+                               if (!type_arg.is_non_null_simple_type ()
+                                   && type_arg.is_weak () != target_type_arg.is_weak ()) {
+                                       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,
@@ -418,6 +432,14 @@ public abstract class Vala.DataType : CodeNode {
                return is_real_struct_type () && !nullable;
        }
 
+       bool is_non_null_simple_type () {
+               unowned Struct s = data_type as Struct;
+               if (s != null && s.is_simple_type ()) {
+                       return !nullable;
+               }
+               return false;
+       }
+
        /**
         * Returns whether the value needs to be disposed, i.e. whether
         * allocated memory or other resources need to be released when