Fix external function declarations with class typedef references (#6433).

Changes

@@ -46,6 +46,7 @@ Verilator 5.041 devel
 * Fix parameter implicit type from string (#6414). [Alex Solomatnikov]
 * Fix parsing for sequence expressions (#6427). [Bartłomiej Chmiel, Antmicro Ltd.]
 * Fix resolving parameters (#6388) (#6418) (#6421) (#6438) (#6429). [Artur Bieniek, Antmicro Ltd.]
+* Fix external function declarations with class typedef references (#6433).
 
 
 Verilator 5.040 2025-08-30

src/V3LinkDot.cpp

@@ -917,6 +917,14 @@ class LinkDotFindVisitor final : public VNVisitor {
             classp->addStmtsp(nodep);
             nodep->isExternDef(true);  // So we check there's a matching extern
             nodep->classOrPackagep()->unlinkFrBack()->deleteTree();
+            // Any "Type::" reference in the function's IO are really "MovedToClass::" references
+            if (nodep->fvarp())
+                nodep->fvarp()->foreach([this, classp](AstClassOrPackageRef* refp) {  //
+                    if (refp->name() == classp->name() && !refp->paramsp()) {
+                        UINFO(9, "Cleaning up external function type for class " << refp);
+                        pushDeletep(refp->unlinkFrBack());
+                    }
+                });
         }
     }
 

test_regress/t/t_class_extern_typeref.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_class_extern_typeref.v

@@ -0,0 +1,28 @@
+// 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
+
+class uvm_process_guard#(type T=int);
+  T m_context;
+  extern function T get_context();
+endclass
+
+// When this moves into class, note it's not uvm_process_guard#()::T
+// but rather the T specific to the parameterized class
+function uvm_process_guard::T uvm_process_guard::get_context();
+  return this.m_context;
+endfunction
+
+class uvm_sequence_base;
+  typedef uvm_process_guard#(uvm_sequence_base) m_guard_t;
+endclass
+
+module t;
+  initial begin
+    uvm_sequence_base c;
+    c = new;
+    $finish;
+  end
+endmodule