Verilog Translator

The stack trace:

java.lang.IllegalArgumentException
    at ru.ispras.fortress.util.InvariantChecks.checkTrue(InvariantChecks.java:53)
    at ru.ispras.fortress.util.InvariantChecks.checkTrue(InvariantChecks.java:38)
    at ru.ispras.fortress.util.InvariantChecks.checkNotNull(InvariantChecks.java:95)
    at ru.ispras.verilog.parser.elaborator.VerilogDesign$Builder.addParameter(VerilogDesign.java:64)
    at ru.ispras.verilog.parser.elaborator.VerilogElaborator.defineParameter(VerilogElaborator.java:636)
    at ru.ispras.verilog.parser.elaborator.VerilogElaborator.createBindings(VerilogElaborator.java:515)
    at ru.ispras.verilog.parser.elaborator.VerilogElaborator.createBindings(VerilogElaborator.java:481)
    at ru.ispras.verilog.parser.elaborator.VerilogElaborator.expand(VerilogElaborator.java:275)
    at ru.ispras.verilog.parser.elaborator.VerilogElaborator.start(VerilogElaborator.java:181)
    at ru.ispras.verilog.parser.VerilogSyntaxBackends.start(VerilogSyntaxBackends.java:56)
    at ru.ispras.verilog.parser.VerilogTranslator.start(VerilogTranslator.java:163)
    at ru.ispras.verilog.parser.sample.VerilogPrinter.main(VerilogPrinter.java:45)
    at ru.ispras.verilog.parser.VerilogIeeeTestCase.runTest(VerilogIeeeTestCase.java:1813)
    at ru.ispras.verilog.parser.VerilogIeeeTestCase.runTest(VerilogIeeeTestCase.java:1799)
    at ru.ispras.verilog.parser.VerilogIeeeTestCase.runTest_10_04_05_1(VerilogIeeeTestCase.java:929)

The target Verilog module:

// IEEE Std 1364-2005
//   10. Tasks and functions
//     10.4 Functions and function calling
//       10.4.5 Use of constant functions
//         This example defines a function called clogb2 that returns an integer with the value of
//         the ceiling of the log base 2.

module ram_model (address, write, chip_select, data);
  parameter data_width = 8;
  parameter ram_depth = 256;
  localparam addr_width = clogb2(ram_depth);
  input [addr_width - 1:0] address;
  input write, chip_select;
  inout [data_width - 1:0] data;

  //define the clogb2 function
  function integer clogb2;
    input [31:0] value;
    begin
      value = value - 1;
      for (clogb2 = 0; value > 0; clogb2 = clogb2 + 1)
        value = value >> 1;
      end
  endfunction

  reg [data_width - 1:0] data_store[0:ram_depth - 1];

  //the rest of the ram model
endmodule