Add error on localparam value from hierarchical path (#6456).

Changes

@@ -17,6 +17,7 @@ Verilator 5.041 devel
 * Add configure `--enable-asan` to compile verilator_bin with the address sanitizer (#6404). [Geza Lore]
 * Add $(LDFLAGS) and $(LIBS) to when building shared libraries (#6425) (#6426). [Ahmed El-Mahmoudy]
 * Add ASSIGNEQEXPR when use `=` inside expressions (#5567). [Ethan Sifferman]
+* Add error on localparam value from hierarchical path (#6456). [Luca Rufer]
 * Deprecate sensitivity list on public_flat_rw attributes (#6443). [Geza Lore]
 * Support modports referencing clocking blocks (#4555) (#6436). [Ryszard Rozak, Antmicro Ltd.]
 * Support pure functions in sensitivity lists (#6393). [Krzysztof Bieganski, Antmicro Ltd.]

src/V3Param.cpp

@@ -1416,6 +1416,13 @@ class ParamVisitor final : public VNVisitor {
         if (nodep->user2SetOnce()) return;  // Process once
         iterateChildren(nodep);
         if (nodep->isParam()) {
+            // See if any Future before we process
+            if (nodep->valuep())
+                nodep->valuep()->foreach([&](const AstVarXRef* refp) {
+                    refp->v3error("Parameter values cannot be hierarchical"
+                                  " (IEEE 1800-2023 6.20.2): "
+                                  << nodep->prettyNameQ());
+                });
             if (!nodep->valuep() && !VN_IS(m_modp, Class)) {
                 nodep->v3error("Parameter without default value is never given value"
                                << " (IEEE 1800-2023 6.20.1): " << nodep->prettyNameQ());

test_regress/t/t_interface_array_parameter_access.py

@@ -9,7 +9,7 @@
 
 import vltest_bootstrap
 
-test.scenarios('simulator')
+test.scenarios('simulator_st')
 
 test.compile()
 

test_regress/t/t_interface_array_parameter_access.v

@@ -12,7 +12,7 @@ interface intf
 endinterface
 
 module sub (intf.modp the_intf_port [4]);
-    localparam int intf_foo = the_intf_port[0].FOO;
+    const int intf_foo = the_intf_port[0].FOO;
 
     initial begin
         if (intf_foo != 4) $stop;

test_regress/t/t_interface_localparam.v

@@ -35,7 +35,7 @@ module Core(
 );
 
    // this will constify and valDiv2 will have the default value
-   localparam valDiv4Upper = intf.valDiv2;
+   const int valDiv4Upper = intf.valDiv2;
 
    SimpleIntf #(.VAL(68)) core_intf ();
 

test_regress/t/t_interface_param_acc_bits.py

@@ -9,7 +9,7 @@
 
 import vltest_bootstrap
 
-test.scenarios('simulator')
+test.scenarios('simulator_st')
 
 test.compile()
 

test_regress/t/t_interface_param_acc_bits.v

@@ -17,7 +17,7 @@ endinterface
 
 module t ();
    simple_bus sb_intf();
-   localparam LP = $bits(sb_intf.payload.data);
+   const int LP = $bits(sb_intf.payload.data);
    simple_bus #(.PARAMETER($bits(sb_intf.DUMMY))) simple();
    simple_bus #(.PARAMETER($bits(sb_intf.x))) simple2();
    initial begin

test_regress/t/t_interface_parameter_access.py

@@ -9,7 +9,7 @@
 
 import vltest_bootstrap
 
-test.scenarios('simulator')
+test.scenarios('simulator_st')
 
 test.compile()
 

test_regress/t/t_interface_parameter_access.v

@@ -45,9 +45,9 @@ module t (/*AUTOARG*/
                       .intf_array (array_interface)
                       );
 
-   localparam THE_TOP_FOO = the_interface.FOO;
+   const int THE_TOP_FOO = the_interface.FOO;
-   localparam THE_TOP_FOO_BITS = $bits({the_interface.FOO, the_interface.FOO});
+   const int THE_TOP_FOO_BITS = $bits({the_interface.FOO, the_interface.FOO});
-   localparam THE_ARRAY_FOO = array_interface[0].FOO;
+   const int THE_ARRAY_FOO = array_interface[0].FOO;
 
    initial begin
       if (THE_TOP_FOO != 5) begin
@@ -75,12 +75,12 @@ module testmod
    test_if.mp intf_array [1:0]
    );
 
-   localparam THE_FOO = intf.FOO;
+   const int THE_FOO = intf.FOO;
-   localparam THE_OTHER_FOO = intf_no_mp.FOO;
+   const int THE_OTHER_FOO = intf_no_mp.FOO;
-   localparam THE_ARRAY_FOO = intf_array[0].FOO;
+   const int THE_ARRAY_FOO = intf_array[0].FOO;
-   localparam THE_BAR = intf.BAR;
+   const int THE_BAR = intf.BAR;
-   localparam THE_OTHER_BAR = intf_no_mp.BAR;
+   const int THE_OTHER_BAR = intf_no_mp.BAR;
-   localparam THE_ARRAY_BAR = intf_array[0].BAR;
+   const int THE_ARRAY_BAR = intf_array[0].BAR;
 
    always @(posedge clk) begin
       if (THE_FOO != 5) begin

test_regress/t/t_param_hier_bad.out

@@ -0,0 +1,6 @@
+%Error: t/t_param_hier_bad.v:26:32: Parameter values cannot be hierarchical (IEEE 1800-2023 6.20.2): 'SUB_Y'
+                                  : ... note: In instance 't'
+   26 |   localparam int SUB_Y = u_sub.Y;   
+      |                                ^
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: Exiting due to

test_regress/t/t_param_hier_bad.py

@@ -0,0 +1,16 @@
+#!/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('linter')
+
+test.lint(fails=True, expect_filename=test.golden_filename)
+
+test.passes()

test_regress/t/t_param_hier_bad.v

@@ -0,0 +1,36 @@
+// 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\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
+// verilog_format: on
+
+module sub #(
+  parameter int X = 1
+) ();
+
+  localparam int Y = X;
+  localparam int Z = X;
+
+endmodule
+
+module t;
+  localparam int MY_X = 2;
+
+  sub #(.X(MY_X)) u_sub ();
+
+  localparam int SUB_Y = u_sub.Y;  // <--- BAD: IEEE 1800-2023 6.20.2 no hierarchical
+
+  initial begin
+    `checkd(SUB_Y, 1);
+    `checkd(u_sub.X, 2);
+    `checkd(u_sub.Y, 1);
+    `checkd(u_sub.Z, 2);
+    $finish;
+  end
+
+endmodule