Bad typing rule? Type checking errors in NoPCM and SWHS DDs

[balacij]

Related to #3093

From NoPCM (shared with SWHS):

`tauW` exposes ill-typed expressions!
  - ERROR: Associative arithmetic operation expects all operands to be of the same expected type (Real).
    Received:
    - Rational
    - Rational

From SWHS:

`tauW` exposes ill-typed expressions!
  - ERROR: Associative arithmetic operation expects all operands to be of the same expected type (Real).
    Received:
    - Rational
    - Rational

`eta` exposes ill-typed expressions!
  - ERROR: Associative arithmetic operation expects all operands to be of the same expected type (Real).
    Received:
    - Rational
    - Rational

`tauSP` exposes ill-typed expressions!
  - ERROR: Associative arithmetic operation expects all operands to be of the same expected type (Real).
    Received:
    - Rational
    - Rational

`tauLP` exposes ill-typed expressions!
  - ERROR: Associative arithmetic operation expects all operands to be of the same expected type (Real).
    Received:
    - Rational
    - Rational

[balacij]

Well, it's not really a bad typing rule. Each of these are "okay" (at least w.r.t. the errors shown), except that they use addRe or mulRe, when they need to be using, the non-existent, addRat or mulRat. I think we can merge addRe and addI into just add (and then hide it behind $+ again).

[JacquesCarette]

I agree about merging addRe and addI and hiding.

The errors are real (pun intended) basically because none of those things should be Rational, that seems like a plain hack that should be fixed.

[JacquesCarette]

All of these are fixed now.