Fix passing typedef value as parameter (#6543)

src/V3LinkDot.cpp

@@ -2889,14 +2889,14 @@ class LinkDotResolveVisitor final : public VNVisitor {
         dtypep = dtypep->skipRefp();
         while (true) {
             if (const AstBracketArrayDType* const adtypep = VN_CAST(dtypep, BracketArrayDType)) {
-                dtypep = adtypep->childDTypep()->skipRefp();
+                dtypep = adtypep->subDTypep()->skipRefp();
             } else if (const AstDynArrayDType* const adtypep = VN_CAST(dtypep, DynArrayDType)) {
-                dtypep = adtypep->childDTypep()->skipRefp();
+                dtypep = adtypep->subDTypep()->skipRefp();
             } else if (const AstQueueDType* const adtypep = VN_CAST(dtypep, QueueDType)) {
-                dtypep = adtypep->childDTypep()->skipRefp();
+                dtypep = adtypep->subDTypep()->skipRefp();
             } else if (const AstUnpackArrayDType* const adtypep
                        = VN_CAST(dtypep, UnpackArrayDType)) {
-                dtypep = adtypep->childDTypep()->skipRefp();
+                dtypep = adtypep->subDTypep()->skipRefp();
             } else {
                 break;
             }

src/V3Param.cpp

@@ -62,6 +62,7 @@
 
 #include <cctype>
 #include <deque>
+#include <map>
 #include <memory>
 #include <vector>
 
@@ -1265,6 +1266,7 @@ public:
 class ParamVisitor final : public VNVisitor {
     // NODE STATE
     // AstNodeModule::user1 -> bool: already fixed level (temporary)
+    // AstNodeDType::user2  -> bool: already visited from typedef
 
     // STATE - across all visitors
     ParamState& m_state;  // Common state
@@ -1279,6 +1281,8 @@ class ParamVisitor final : public VNVisitor {
     // STATE - for current visit position (use VL_RESTORER)
     AstNodeModule* m_modp;  // Module iterating
     string m_generateHierName;  // Generate portion of hierarchy name
+    std::map<const AstRefDType*, bool>
+        m_isCircularTypeCache;  // Caches return values of `V3Width::isCircularType` calls
 
     // METHODS
 
@@ -1413,6 +1417,25 @@ class ParamVisitor final : public VNVisitor {
             processWorkQ();
         }
     }
+    void visit(AstRefDType* nodep) override {
+        const auto iter = m_isCircularTypeCache.find(nodep);
+        bool isCircular;
+        if (iter != m_isCircularTypeCache.end()) {
+            isCircular = iter->second;
+        } else {
+            isCircular = V3Width::isCircularType(nodep);
+            m_isCircularTypeCache.emplace(nodep, isCircular);
+        }
+        if (isCircular) {
+            nodep->v3error("Typedef's type is circular: " << nodep->prettyName());
+        } else if (nodep->typedefp() && nodep->subDTypep()
+                   && (VN_IS(nodep->subDTypep()->skipRefOrNullp(), IfaceRefDType)
+                       || VN_IS(nodep->subDTypep()->skipRefOrNullp(), ClassRefDType))
+                   && !nodep->skipRefp()->user2SetOnce()) {
+            iterate(nodep->skipRefp());
+        }
+        iterateChildren(nodep);
+    }
     void visit(AstCell* nodep) override {
         checkParamNotHier(nodep->paramsp());
         visitCellOrClassRef(nodep, VN_IS(nodep->modp(), Iface));

src/V3Width.cpp

@@ -2108,12 +2108,6 @@ class WidthVisitor final : public VNVisitor {
         UINFO(4, "dtWidthed " << nodep);
     }
     void visit(AstRefDType* nodep) override {
-        if (nodep->doingWidth()) {  // Early exit if have circular parameter definition
-            nodep->v3error("Typedef's type is circular: " << nodep->prettyName());
-            nodep->dtypeSetBit();
-            nodep->doingWidth(false);
-            return;
-        }
         if (nodep->didWidthAndSet()) return;  // This node is a dtype & not both PRELIMed+FINALed
         nodep->doingWidth(true);
         if (nodep->typeofp()) {  // type(typeofp_expression)
@@ -8958,3 +8952,12 @@ AstNode* V3Width::widthGenerateParamsEdit(
     // No WidthRemoveVisitor, as don't want to drop $signed etc inside gen blocks
     return nodep;
 }
+
+bool V3Width::isCircularType(const AstRefDType* nodep) {
+    std::set<const AstRefDType*> visited;
+    while (nodep) {
+        if (!visited.insert(nodep).second) return true;
+        nodep = VN_CAST(nodep->subDTypep(), RefDType);
+    }
+    return false;
+}

src/V3Width.h

@@ -23,6 +23,7 @@
 class AstNetlist;
 class AstNode;
 class AstNodeDType;
+class AstRefDType;
 
 //============================================================================
 
@@ -36,6 +37,8 @@ public:
     // Replace AstSelBit, etc with AstSel/AstArraySel
     // Returns replacement node if nodep was deleted, or null if none.
     static AstNode* widthSelNoIterEdit(AstNode* nodep) VL_MT_DISABLED;
+
+    static bool isCircularType(const AstRefDType* nodep);
 };
 
 #endif  // Guard

test_regress/t/t_param_typedef2.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_param_typedef2.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 Antmicro.
+// SPDX-License-Identifier: CC0-1.0
+
+class Foo #(type T);
+endclass
+
+class Bar #(type T);
+endclass
+
+typedef Bar#(string) s_t;
+
+class Some #(type T);
+  typedef Bar#(string) s_t;
+endclass
+
+module t;
+  initial begin
+    Some#(int)::s_t x[string];
+    Bar#(string) y[string];
+    if ($typename(Foo#(s_t)) != $typename(Foo#(Bar#(string)))) $stop;
+    if ($typename(x) != $typename(y)) $stop;
+    $write("*-* All finished *-*\n");
+    $finish;
+  end
+endmodule

test_regress/t/t_typedef_circ_bad.out

@@ -2,4 +2,7 @@
     8 | typedef a_t b_t;
       |         ^~~
         ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: t/t_typedef_circ_bad.v:9:9: Typedef's type is circular: b_t
+    9 | typedef b_t a_t;
+      |         ^~~
 %Error: Exiting due to