[vala/staging] vala: Improve handling of "void" as generic type

[Rico Tzschichholz <ricotz src gnome org>]

commit 7d772d364fc55ab5944abae8173f9256f14711cd
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Mon Nov 18 12:49:12 2019 +0100

    vala: Improve handling of "void" as generic type
    
    Fixes https://gitlab.gnome.org/GNOME/vala/issues/878

 codegen/valaccodebasemodule.vala |  4 ++++
 tests/generics/void-type.vala    | 35 +++++++++++++++++++++++++++++++++++
 vala/valasemanticanalyzer.vala   |  1 +
 3 files changed, 40 insertions(+)
---
diff --git a/codegen/valaccodebasemodule.vala b/codegen/valaccodebasemodule.vala
index 488ecfbff..5c8a097c2 100644
--- a/codegen/valaccodebasemodule.vala
+++ b/codegen/valaccodebasemodule.vala
@@ -2573,6 +2573,10 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
         * Create a temporary variable and return lvalue access to it
         */
        public TargetValue create_temp_value (DataType type, bool init, CodeNode node_reference, bool? 
value_owned = null) {
+               if (type is VoidType) {
+                       Report.error (node_reference.source_reference, "internal: 'void' not supported as 
variable type");
+               }
+
                var local = new LocalVariable (type.copy (), "_tmp%d_".printf (next_temp_var_id++), null, 
node_reference.source_reference);
                local.init = init;
                if (value_owned != null) {
diff --git a/tests/generics/void-type.vala b/tests/generics/void-type.vala
new file mode 100644
index 000000000..b44178259
--- /dev/null
+++ b/tests/generics/void-type.vala
@@ -0,0 +1,35 @@
+class Foo<G> : Object {
+       public G prop { get; set; }
+}
+
+delegate G FooFunc<G> (G g);
+
+void foo () {
+}
+
+void main () {
+       {
+               var f = new Thread<void> (null, foo);
+       }
+       {
+               Thread f = new Thread<void> (null, foo);
+       }
+       {
+               Thread<void> f = new Thread<void> (null, foo);
+       }
+       {
+               FooFunc f = (FooFunc) foo;
+               f (null);
+       }
+       {
+               FooFunc<void> f = (FooFunc<void>) foo;
+               f (null);
+       }
+       {
+               FooFunc<void> f = foo;
+               f (null);
+       }
+       {
+               var f = new Foo<void> ();
+       }
+}
diff --git a/vala/valasemanticanalyzer.vala b/vala/valasemanticanalyzer.vala
index 25d0c40dd..41a815742 100644
--- a/vala/valasemanticanalyzer.vala
+++ b/vala/valasemanticanalyzer.vala
@@ -1344,6 +1344,7 @@ public class Vala.SemanticAnalyzer : CodeVisitor {
        void check_type_argument (DataType type_arg) {
                if (type_arg is GenericType
                    || type_arg is PointerType
+                   || type_arg is VoidType
                    || is_reference_type_argument (type_arg)
                    || is_nullable_value_type_argument (type_arg)
                    || is_signed_integer_type_argument (type_arg)