gm2 rejecting a constant statement as variable

[Alice Osako]

    I am currently intending to
      work with M2PP (https://github.com/m2sf/m2pp), and for this
      purpose I have been writing a Makefile to compile all of the
      components and build the preprocessor. I have run the
      configuration script (using the settings for ISO, GNU, POSIX,
      32/64) and started preparing the make targets for the individual
      sub-modules.
      
      However, I have come across a surprising problem: several constant
      initializations are being flagged as involving one or more
      variables. I have confirmed that the assignments in question are,
      in fact, constant, but the compiler is saying that they aren't.
      
      For example, the constant declaration:
      
      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      BitsInUse =
          ORD(AddressableBits > MaxBits) * MaxBits +
          ORD(AddressableBits <= MaxBits) * AddressableBits;
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      
      Gives the following error:
      
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    src/imp/Hash.mod:34:13:
      error: In implementation module ‘Hash’: in assignment, cannot
      assign a variable to a constant ‘BitsInUse’
         34 |   BitsInUse =
            |             ^
      src/imp/Hash.mod:34:3: error: designator ‘BitsInUse’ is declared
      as a CONST
         34 |   BitsInUse =
            |   ^~~~~~~~~
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      
      I have confirmed that both AddressableBits and MaxBits are constants, and the application of +, *, and
      ORD() on constants clearly should be
      recognized as constants as well. Indeed, immediately following
      this initialization is the constant declaration
      
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      TTP16  =
      ORD(AddressableBits>16) * 65535 + 1;
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
      compiles without complaint.
      
      (I am assuming that ORD(FALSE) should return zero, and ORD(TRUE) should return
      one, which it clearly is the intended use in this code - in
      effect, a pocket ternary _expression_ that only works with numeric
      values.)
    
      I noted that the error message does not specify the supposed
      variable in question, which would make it harder to debug even if
      there were a variable in the assignment.
      
      Am I missing something? I am not inclined to assume that this is a
      compiler fault, but if it isn't, I am not certain why it would see
      a variable in these assignments.