Fix chain call of abstract class constructor (#3868) (#3883)

docs/CONTRIBUTORS

@@ -45,6 +45,7 @@ HungMingWu
 HyungKi Jeong
 Iru Cai
 Ivan Vnučec
+Ilya Barkov
 Iztok Jeras
 Jake Merdich
 James Hanlon

src/V3Width.cpp

@@ -3626,6 +3626,10 @@ private:
                 // Either made explicitly or V3LinkDot made implicitly
                 classp->v3fatalSrc("Can't find class's new");
             }
+            if (classp->isVirtual()) {
+                nodep->v3error(
+                    "Illegal to call 'new' using an abstract virtual class (IEEE 1800-2017 8.21)");
+            }
         } else {  // super.new case
             // in this case class and taskp() should be properly linked in V3LinkDot.cpp during
             // "super" reference resolution
@@ -3634,10 +3638,6 @@ private:
             UASSERT_OBJ(nodep->taskp(), nodep, "Unlinked taskp()");
             nodep->dtypeFrom(nodep->taskp());
         }
-        if (classp->isVirtual()) {
-            nodep->v3error(
-                "Illegal to call 'new' using an abstract virtual class (IEEE 1800-2017 8.21)");
-        }
         userIterate(nodep->taskp(), nullptr);
         processFTaskRefArgs(nodep);
     }

test_regress/t/t_class_virtual_chain_ctor.pl

@@ -0,0 +1,16 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2023 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(vlt => 1);
+
+lint();
+
+ok(1);
+1;

test_regress/t/t_class_virtual_chain_ctor.v

@@ -0,0 +1,34 @@
+// DESCRIPTION: Verilator: Check that an abstract class' contstructor
+// can be called indirectly from a constructor of a derived class.
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2023 by Ilya Barkov
+// SPDX-License-Identifier: CC0-1.0
+
+// It's illegal to call
+//     VBase b = new;
+// see t_class_virtual_bad
+virtual class VBase;
+   function new(); endfunction
+endclass
+
+// Another constructor of an abstact class in the chain
+virtual class VChild1 extends VBase;
+   function new();
+      super.new();
+   endfunction
+endclass
+
+// It shall be perfectly fine to create an instance of a
+// non-abstract VChild2
+class VChild2 extends VChild1;
+   function new();
+      super.new();
+   endfunction
+endclass
+
+module t;
+   initial begin
+      VChild2 c = new;
+   end
+endmodule