Fix internal error when derived class calls this.randomize() with inherited rand members (#7229) (#7234)

src/V3Randomize.cpp

@@ -730,6 +730,8 @@ class ConstraintExprVisitor final : public VNVisitor {
     AstClass* const m_classp;
     AstNodeFTask* const m_inlineInitTaskp;  // Method to add write_var calls to
                                             // (may be null, then new() is used)
+    AstNodeFTask* const m_memberselInitTaskp;  // Fallback for membersel write_var when
+                                               // classp has no randomize() (inherited members)
     AstVar* const m_genp;  // VlRandomizer variable of the class
     AstVar* m_randModeVarp;  // Relevant randmode state variable
     bool m_wantSingle = false;  // Whether to merge constraint expressions with LOGAND
@@ -1248,6 +1250,9 @@ class ConstraintExprVisitor final : public VNVisitor {
                     varp->user3(true);
                     if (membersel) {
                         initTaskp = VN_AS(m_memberMap.findMember(classp, "randomize"), NodeFTask);
+                        // Inherited rand members may belong to a base class
+                        // that has no randomize(); use the caller's function
+                        if (!initTaskp) initTaskp = m_memberselInitTaskp;
                         UASSERT_OBJ(initTaskp, classp, "No randomize() in class");
                     } else {
                         initTaskp = VN_AS(m_memberMap.findMember(classp, "new"), NodeFTask);
@@ -2388,9 +2393,11 @@ public:
     // CONSTRUCTORS
     explicit ConstraintExprVisitor(AstClass* classp, VMemberMap& memberMap, AstNode* nodep,
                                    AstNodeFTask* inlineInitTaskp, AstVar* genp,
-                                   AstVar* randModeVarp, std::set<std::string>& writtenVars)
+                                   AstVar* randModeVarp, std::set<std::string>& writtenVars,
+                                   AstNodeFTask* memberselInitTaskp = nullptr)
         : m_classp{classp}
         , m_inlineInitTaskp{inlineInitTaskp}
+        , m_memberselInitTaskp{memberselInitTaskp}
         , m_genp{genp}
         , m_randModeVarp{randModeVarp}
         , m_memberMap{memberMap}
@@ -3979,7 +3986,7 @@ class RandomizeVisitor final : public VNVisitor {
                 if (constrp->itemsp()) expandUniqueElementList(constrp->itemsp());
                 if (constrp->itemsp()) lowerDistConstraints(taskp, constrp->itemsp());
                 ConstraintExprVisitor{classp, m_memberMap,  constrp->itemsp(), nullptr,
-                                      genp,   randModeVarp, m_writtenVars};
+                                      genp,   randModeVarp, m_writtenVars,     randomizep};
                 if (constrp->itemsp()) {
                     taskp->addStmtsp(wrapIfConstraintMode(
                         nodep, constrp, constrp->itemsp()->unlinkFrBackWithNext()));

test_regress/t/t_randomize_derived_this.py

@@ -0,0 +1,21 @@
+#!/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')
+
+if not test.have_solver:
+    test.skip("No constraint solver installed")
+
+test.compile()
+
+test.execute()
+
+test.passes()

test_regress/t/t_randomize_derived_this.v

@@ -0,0 +1,76 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 PlanV GmbH
+// 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\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
+// verilog_format: on
+
+// Test: this.randomize() called in derived class with inherited rand members
+// and constraints from base class. Verifies IS_RANDOMIZED propagation and
+// membersel write_var fallback for ancestor classes.
+
+class sub_cfg_c;
+  rand bit enabled;
+  constraint defaults {
+    soft enabled == 1'b0;
+  }
+endclass
+
+class base_c;
+  rand sub_cfg_c cfg;
+  rand int unsigned watchdog;
+
+  constraint override_cons {
+    cfg.enabled == 1'b1;
+  }
+
+  constraint watchdog_range {
+    watchdog inside {[32'd50:32'd200]};
+  }
+
+  function new();
+    cfg = new();
+  endfunction
+endclass
+
+// Derived class: no additional rand members, calls this.randomize()
+class derived_c extends base_c;
+  function int do_randomize();
+    return this.randomize();
+  endfunction
+endclass
+
+// Deep inheritance: grandchild with no rand members
+class grandchild_c extends derived_c;
+  function int do_rand_deep();
+    return this.randomize();
+  endfunction
+endclass
+
+module t;
+  initial begin
+    automatic derived_c d = new();
+    automatic grandchild_c g = new();
+
+    // Test derived class this.randomize()
+    repeat (20) begin
+      `checkd(d.do_randomize(), 1)
+      `checkd(d.cfg.enabled, 1)
+      `checkd(d.watchdog >= 32'd50 && d.watchdog <= 32'd200, 1)
+    end
+
+    // Test deep inheritance this.randomize()
+    repeat (20) begin
+      `checkd(g.do_rand_deep(), 1)
+      `checkd(g.cfg.enabled, 1)
+      `checkd(g.watchdog >= 32'd50 && g.watchdog <= 32'd200, 1)
+    end
+
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+endmodule