Due to awkward module dependencies, some functions had to be moved around to accommodate this change. Two from Types have gone to EvalLiterals, and two to CompState. Everything still compiles just as before though.
However, it is possible that there will still be a problem if the C and C++ compiler have different int sizes, because the constant folding has to know the type at compile time, and thus we have to arbitrarily choose to use the C version. In future, we could perhaps swap all Ints for the appropriate substiution (e.g. Int64) at run-time, based on the flags and prior knowledge about C/C++ int sizes
In particular, evalSimpleLiteral is now much nicer, and the error
messages should be a bit more comprehensible.
The signed types previously used a different version of fromRead that
passed an extra argument that it then didn't use; I've switched back to
the old version now, since it appears not to need it any more.
ErrorReport is of type (Maybe Meta, String), thereby adding an optional code position to error messages.
Die has been changed so that die and dieP are now implemented in terms of dieReport (:: ErrorReport -> m a). This involved changing less code than changing die to be of type ErrorReport -> m a. All that had to be changed directly was that Die instances now implement dieReport instead of die.
Any bits of code that "caught" errors has been changed so that it handles ErrorReport instead of String. This ErrorReport is eventually, in Main, passed to dieIO, which will soon be changed to read the file in and provide the context. Accordingly, MonadIO m has been added as a constraint to dieIO, and dieInternal has been changed to no longer use dieIO (because really we can't add the MonadIO constraint to dieInternal).
Various error messages have been changed. Notably, all instances of fail in ParseOccam have been changed to use die or, wherever possible, dieP. A similar thing has been done in EvalConstants and EvalLiterals.
