Fix typedef of parameterized class for member access (#5977)

Defer RefDType resolution in linkDotPrimary when the classOrPackageRef
target is a typedef to a parameterized class. Previously only direct
class references were deferred, so `typedef outer_cls#(params) drv_t;
drv_t::beat_t x;` would resolve against the generic class which V3Param
later deletes.

src/V3LinkDot.cpp

@@ -5310,6 +5310,11 @@ class LinkDotResolveVisitor final : public VNVisitor {
                     iterate(cpackagep);
                     return;
                 }
+                // Also defer if target is a typedef to a parameterized class (#5977)
+                if (m_statep->forPrimary() && isParamedClassRef(cpackagerefp)) {
+                    iterate(cpackagep);
+                    return;
+                }
                 if (!cpackagerefp->classOrPackageSkipp()) {
                     VSymEnt* const foundp = m_statep->resolveClassOrPackage(
                         m_ds.m_dotSymp, cpackagerefp, true, false, "class/package reference");

test_regress/t/t_class_param_typedef8.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# 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-FileCopyrightText: 2026 Wilson Snyder
+# 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_param_typedef8.v

@@ -0,0 +1,45 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 Leela Pakanati
+// SPDX-License-Identifier: CC0-1.0
+
+// Test for issue #5977: Typedef of parameterized class for member access
+
+// verilog_format: off
+`define stop $stop
+`define checkd(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got=%0d exp=%0d\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
+// verilog_format: on
+
+package pkg;
+  class cls_l0 #(parameter AW = 32);
+    logic [AW-1:0] addr;
+    function new();
+      addr = '0;
+    endfunction
+  endclass
+
+  class cls_l1 #(parameter int AW = 32);
+    typedef cls_l0 #(.AW(AW)) beat_t;
+  endclass
+endpackage
+
+module t;
+  // Typedef of parameterized class, then access member typedef via ::
+  typedef pkg::cls_l1 #(.AW(64)) drv64_t;
+  typedef pkg::cls_l1 #(.AW(128)) drv128_t;
+
+  initial begin
+    // Access class-type typedef member through module-level typedef
+    automatic drv64_t::beat_t item1 = new;
+    automatic drv128_t::beat_t item2 = new;
+    item1.addr = 64'hDEAD_BEEF_CAFE_BABE;
+
+    `checkd(item1.addr, 64'hDEAD_BEEF_CAFE_BABE);
+    `checkd($bits(item1.addr), 64);
+    `checkd($bits(item2.addr), 128);
+
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+endmodule

test_regress/t/t_class_param_typedef8_noinl.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# 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-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.top_filename = "t/t_class_param_typedef8.v"
+
+test.compile(verilator_flags2=['--binary', '-fno-inline'])
+
+test.execute()
+
+test.passes()