Add regression test for class tasks used as expressions

Check that using a class task through an object method call in expression
context reports a compile/elaboration error instead of triggering an assert.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

ivtest/ivltests/sv_class_task_expr_fail.v

@@ -0,0 +1,19 @@
+// Check that using a class task as an expression reports an error.
+
+module test;
+
+  class C;
+    task t;
+    endtask
+  endclass
+
+  C c;
+
+  initial begin
+    int x;
+    c = new;
+    x = c.t();
+    $display("FAILED");
+  end
+
+endmodule

ivtest/regress-vvp.list

@@ -272,6 +272,7 @@ sv_class_prop_nest_obj1		vvp_tests/sv_class_prop_nest_obj1.json
 sv_class_prop_nest_real1	vvp_tests/sv_class_prop_nest_real1.json
 sv_class_prop_nest_str1		vvp_tests/sv_class_prop_nest_str1.json
 sv_class_prop_nest_vec1		vvp_tests/sv_class_prop_nest_vec1.json
+sv_class_task_expr_fail	vvp_tests/sv_class_task_expr_fail.json
 sv_const1			vvp_tests/sv_const1.json
 sv_const2			vvp_tests/sv_const2.json
 sv_const3			vvp_tests/sv_const3.json

ivtest/vvp_tests/sv_class_task_expr_fail.json

@@ -0,0 +1,9 @@
+{
+    "type"          : "CE",
+    "source"        : "sv_class_task_expr_fail.v",
+    "iverilog-args" : [ "-g2005-sv" ],
+    "vlog95" : {
+        "__comment"     : "Classes are not supported",
+        "type"          : "CE"
+    }
+}