Fix class-in-class extends with parameters (#6773).

Changes

@@ -72,6 +72,7 @@ Verilator 5.043 devel
 * Fix `--prof-exec` using `--lib-create`. [Geza Lore]
 * Fix fork scheduling semantics (#6730). [Artur Bieniek, Antmicro Ltd.]
 * Fix internal fault when cross-class calling with DPI (#6735) (#6742). [Matthew Ballance]
+* Fix class-in-class extends with parameters (#6773).
 
 
 Verilator 5.042 2025-11-02

src/V3LinkDot.cpp

@@ -4580,6 +4580,15 @@ class LinkDotResolveVisitor final : public VNVisitor {
                 nodep->taskp(randFuncp);
                 m_curSymp = m_statep->insertBlock(m_curSymp, nodep->name(), randFuncp, m_modp);
             }
+            if (m_insideClassExtParam) {
+                // The reference may point to a method declared in a super class, which is proved
+                // by a parameter. In such a case, it can't be linked at the first stage.
+                // Must not do any linking, because e.g. might find an extends of an upper class
+                // because the current class (under parent) isn't yet importing it's extended class
+                // symbols
+                return;
+            }
+
             VSymEnt* const foundp
                 = m_statep->findSymPrefixed(dotSymp, nodep->name(), baddot, first);
             AstNodeFTask* const taskp
@@ -4593,10 +4602,6 @@ class LinkDotResolveVisitor final : public VNVisitor {
                 nodep->taskp(taskp);
                 nodep->classOrPackagep(foundp->classOrPackagep());
                 UINFO(7, indent() << "Resolved " << nodep);  // Also prints taskp
-            } else if (m_insideClassExtParam) {
-                // The reference may point to a method declared in a super class, which is proved
-                // by a parameter. In such a case, it can't be linked at the first stage.
-                return;
             } else {
                 // Note ParseRef has similar error handling/message output
                 UINFO(7, indent() << "   ErrFtask curSymp=se" << cvtToHex(m_curSymp)

test_regress/t/t_class_class_extends.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(verilator_flags2=['--binary'])
+
+test.execute()
+
+test.passes()

test_regress/t/t_class_class_extends.v

@@ -0,0 +1,113 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2025 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+package uvm_pkg;
+  typedef class uvm_root;
+
+  virtual class uvm_coreservice_t;
+    pure virtual function uvm_root get_root();
+    static function uvm_coreservice_t get();
+      return null;
+    endfunction
+  endclass
+
+  class uvm_default_coreservice_t extends uvm_coreservice_t;
+    virtual function uvm_root get_root();
+      return uvm_root::m_uvm_get_root();
+    endfunction
+  endclass
+
+  virtual class uvm_object;
+  endclass
+
+  class uvm_report_object extends uvm_object;
+    // Note there's no 'virtual' on this function
+    function uvm_report_object uvm_get_report_object();  // Wrong target
+      return null;
+    endfunction
+  endclass
+
+  class uvm_root extends uvm_report_object;
+    static function uvm_root m_uvm_get_root();
+      uvm_root top;
+      top = new();
+      return null;
+    endfunction
+  endclass
+
+  virtual class uvm_process_guard_base extends uvm_object;
+    pure virtual function void do_trigger();
+    // Removing m_process member works around the issue
+    protected process m_target_process;
+    function new();
+      m_target_process = process::self();
+    endfunction
+    function void m_process_guard(uvm_process_guard_base guard);
+      // Removing fork/join works around the issue
+      fork
+        begin
+          if (guard.m_target_process != null) begin
+            guard.do_trigger();
+          end
+        end
+      join_none
+    endfunction
+  endclass
+
+  class uvm_process_guard #(
+      type T = int
+  ) extends uvm_process_guard_base;
+    protected T m_context;
+    function void do_trigger();
+      m_context.process_guard_triggered(this);
+    endfunction
+  endclass
+
+  class uvm_sequence_item;
+    virtual function uvm_report_object uvm_get_report_object();  // Correct target
+      uvm_coreservice_t cs = uvm_coreservice_t::get();
+      return cs.get_root();
+    endfunction
+  endclass
+
+  virtual class uvm_sequence_base extends uvm_sequence_item;
+    typedef uvm_process_guard#(uvm_sequence_base) m_guard_t;
+    function void process_guard_triggered(m_guard_t guard);
+      uvm_pkg::uvm_report_object _local_report_object_arg_;
+      _local_report_object_arg_ = uvm_get_report_object();
+      //  ^ calls uvm_sequence_base->virtual uvm_sequence_item::uvm_get_report_object()
+    endfunction
+  endclass
+
+  virtual class uvm_sequence #(
+      type RSP = int
+  ) extends uvm_sequence_base;
+  endclass
+
+endpackage
+
+module t;
+
+  import uvm_pkg::*;
+
+  class Cls extends uvm_report_object;
+
+    class transaction_sequence extends uvm_sequence #(uvm_object);
+      virtual task body();
+        uvm_pkg::uvm_report_object _local_report_object_arg_;
+        _local_report_object_arg_ = uvm_get_report_object();
+        //                          ^-  calls transaction_sequence->uvm_sequence
+        // ->uvm_sequence_base->virtual uvm_sequence_item::uvm_get_report_object();
+      endtask
+    endclass
+
+  endclass
+
+  initial begin
+    Cls c = new();
+    $finish;
+  end
+endmodule