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.fortress.expression.ExprTreeWalker.visitNode(ExprTreeWalker.java:111)
    at ru.ispras.verilog.parser.processor.VerilogStaticChecker.checkReference(VerilogStaticChecker.java:314)
    at ru.ispras.verilog.parser.processor.VerilogStaticChecker.checkReference(VerilogStaticChecker.java:331)
    at ru.ispras.verilog.parser.processor.VerilogStaticChecker.checkReference(VerilogStaticChecker.java:353)
    at ru.ispras.verilog.parser.processor.VerilogStaticChecker.onAssignStatementBegin(VerilogStaticChecker.java:106)
    at ru.ispras.verilog.parser.walker.VerilogNodeVisitor$3.onBegin(VerilogNodeVisitor.java:265)
    at ru.ispras.verilog.parser.walker.VerilogNodeVisitor.onBegin(VerilogNodeVisitor.java:700)
    at ru.ispras.verilog.parser.core.TreeWalker.onBegin(TreeWalker.java:100)
    at ru.ispras.verilog.parser.core.TreeWalker.start(TreeWalker.java:85)
    at ru.ispras.verilog.parser.VerilogSyntaxBackend.start(VerilogSyntaxBackend.java:80)
    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_17_02_04_4_1(VerilogIeeeTestCase.java:1455)

// IEEE Std 1364-2005
//   17. System tasks and functions
//     17.2 File input-output system tasks and functions
//       17.2.4 Reading data from a file
//         17.2.4.4 Reading binary data
//           The example reads a binary data from the file specified by fd into the reg myreg or
//           the memory mem. The start is an optional argument. If present, start shall be used as
//           the address of the first element in the memory to be loaded. If not present, the lowest
//           numbered location in the memory shall be used. The count is an optional argument. If
//           present, count shall be the maximum number of locations in mem that shall be loaded. If
//           not supplied, the memory shall be filled with what data are available. The start and
//           count are ignored if $fread is loading a reg.

module test;
  integer code, fd;
  reg myreg, start;
  integer count;

  initial begin
    code = $fread (myreg, fd);
    code = $fread (mem, fd);
    code = $fread (mem, fd, start);
    code = $fread (mem, fd, start, count);
    code = $fread (mem, fd, , count);
  end
endmodule