Fix parameterized virtual interface references that have no model references (#4286).

Fixes #4286.

Changes

@@ -26,6 +26,7 @@ Verilator 5.045 devel
 * Support `extern module` as a forward-declaration that is ignored.
 * Remove deprecated `--xml-only`.
 * Remove deprecated `--make cmake`.
+* Fix parameterized virtual interface references that have no model references (#4286).
 * Fix variable reference lookup for module-level variables (#6741) (#6882). [Yilou Wang]
 * Fix MULTIDRIVEN with task and default driver (#4045) (#6858). [em2machine]
 * Fix false CASEOVERLAP case item expression lint (#6825) (#6886). [Luca Colagrande]

src/V3LinkDot.cpp

@@ -1076,8 +1076,8 @@ class LinkDotFindVisitor final : public VNVisitor {
     void visit(AstTypeTable*) override {}  // FindVisitor::
     void visit(AstConstPool*) override {}  // FindVisitor::
     void visit(AstIfaceRefDType* nodep) override {  // FindVisitor::
-        if (m_statep->forPrimary() && nodep->isVirtual() && nodep->ifacep()
-            && !nodep->ifacep()->user3()) {
+        if ((m_statep->forPrimary() || m_statep->forParamed()) && nodep->isVirtual()
+            && nodep->ifacep() && !nodep->ifacep()->user3()) {
             m_virtIfaces.push_back(nodep->ifacep());
             nodep->ifacep()->user3(true);
         }

test_regress/t/t_interface_virtual_nocell.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2025 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
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile()
+
+test.execute()
+
+test.passes()

test_regress/t/t_interface_virtual_nocell.v

@@ -0,0 +1,30 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2026 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+interface mem_if #(
+    int unsigned ADDR_SIZE = 16
+);
+endinterface
+
+module t;
+  class Cls #(
+      type T = int
+  );
+  endclass
+
+  // Note the referred-to virtual class is only used here, not instantiated
+  typedef Cls#(virtual mem_if #(8)) cls_mem_if_t;
+  typedef Cls#(virtual mem_if #()) cls_def_if_t;
+
+  initial begin
+    cls_mem_if_t c;
+    cls_def_if_t d;
+    c = new;
+    d = new;
+    $finish;
+  end
+
+endmodule