Fix DPI under param class (#6733 partial)

src/V3LinkResolve.cpp

@@ -249,10 +249,6 @@ class LinkResolveVisitor final : public VNVisitor {
             letp->user2(false);
             return;
         }
-        if (nodep->taskp() && !nodep->scopeNamep()
-            && (nodep->taskp()->dpiContext() || nodep->taskp()->dpiExport())) {
-            nodep->scopeNamep(new AstScopeName{nodep->fileline(), false});
-        }
     }
 
     void visit(AstCaseItem* nodep) override {

src/V3Task.cpp

@@ -711,8 +711,9 @@ class TaskVisitor final : public VNVisitor {
         if (needSyms) ccallp->argTypes("vlSymsp");
 
         if (refp->taskp()->dpiContext()) {
-            AstScopeName* const snp = refp->scopeNamep()->unlinkFrBack();
+            AstScopeName* const snp = refp->scopeNamep();
             UASSERT_OBJ(snp, refp, "Missing scoping context");
+            snp->unlinkFrBack();
             FileLine* const flp = refp->fileline();
             // __Vscopep
             ccallp->addArgsp(snp);

src/V3Width.cpp

@@ -6792,6 +6792,10 @@ class WidthVisitor final : public VNVisitor {
             nodep->v3error("Cannot call non-static member function "
                            << nodep->prettyNameQ() << " without object (IEEE 1800-2023 8.10)");
         }
+        if (nodep->taskp() && !nodep->scopeNamep()
+            && (nodep->taskp()->dpiContext() || nodep->taskp()->dpiExport())) {
+            nodep->scopeNamep(new AstScopeName{nodep->fileline(), false});
+        }
         // And do the arguments to the task/function too
         processFTaskRefArgs(nodep);
         nodep->addPinsp(withp);

test_regress/t/t_dpi_class_param.cpp

@@ -0,0 +1,15 @@
+// -*- mode: C++; c-file-style: "cc-mode" -*-
+//*************************************************************************
+//
+// Copyright 2024 by Antmicro. 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
+//
+//*************************************************************************
+
+extern "C" int dpii_add() {
+    static int s_i;
+    return ++s_i;
+}

test_regress/t/t_dpi_class_param.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.pli_filename])
+
+test.execute()
+
+test.passes()

test_regress/t/t_dpi_class_param.v

@@ -0,0 +1,46 @@
+// 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
+
+// verilog_format: off
+`define stop $stop
+`define checkd(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got=%0d exp=%0d (%s !== %s)\n", `__FILE__,`__LINE__, (gotv), (expv), `"gotv`", `"expv`"); `stop; end while(0);
+// verilog_format: on
+
+module t;
+  import "DPI-C" context function int dpii_add();
+
+  virtual class uvm_sequence #(
+      type RSP = int
+  );
+  endclass
+
+  class Cls extends uvm_sequence #();
+    virtual function void check_reg();
+      int paths[$];
+      int i;
+      paths.push_back(1);
+      paths.push_back(2);
+      foreach (paths[p]) begin
+        i = dpii_add();
+      end
+    endfunction
+  endclass
+
+  initial begin
+    Cls c;
+    int i;
+    c = new;
+    i = dpii_add();
+    `checkd(i, 1);
+
+    c.check_reg();
+
+    i = dpii_add();
+    `checkd(i, 4);
+    $finish;
+  end
+
+endmodule