Handle vpiUnionVar

Signed-off-by: Rafal Kapuscik <rkapuscik@antmicro.com>

systemverilog-plugin/UhdmAst.cc

diff --git a/systemverilog-plugin/UhdmAst.cc b/systemverilog-plugin/UhdmAst.cc
index 3f6f148..64a0168 100644
--- a/systemverilog-plugin/UhdmAst.cc
+++ b/systemverilog-plugin/UhdmAst.cc
@@ -1879,7 +1879,7 @@
         delete node;
     });
     auto type = vpi_get(vpiType, obj_h);
-    if (type == vpiEnumVar || type == vpiStructVar) {
+    if (type == vpiEnumVar || type == vpiStructVar || type == vpiUnionVar) {
         visit_default_expr(obj_h);
     }
     current_node->is_custom_type = true;
@@ -3510,6 +3510,7 @@
         case vpiStructNet:
         case vpiArrayNet:
         case vpiStructVar:
+        case vpiUnionVar:
         case vpiEnumVar:
         case vpiShortIntVar:
         case vpiIntVar:
@@ -3770,6 +3771,7 @@
     case vpiEnumNet:
     case vpiStructVar:
     case vpiStructNet:
+    case vpiUnionVar:
         process_custom_var();
         break;
     case vpiShortIntVar: