Known bugs in PolyP

Version 1.3

• Context simplification errors:
  • Problem: currently the context simplification algorithm simply removes all contexts without type variables. This can err in two ways: firstly ill-typed programs can be accepted (too much simplification, for example removing a bad context like Monad Tree =>) and secondly well-typed programs can be rejected (by hugs) (too little simplification, for example Monad (State s) is not simplified away.)
  • Solution: improve the context simplification algorithm. Extend PolyP to handle class and instance declarations so that the simlification rules can be given in the prelude file(s).
  • Almost solution: Add a PolyP-flag to allow explicit types not to be generated. (The types are there to get around the monomorphism restriction, and it usually bites at the same time as this bug, so the gain might be small.)
  • Work-around: Make unwanted contexts variable-free by inserting an explicit type somewhere.
• Several (minor?) parser bugs: "\" is accepted (should be "\\")