This makes it possible to mark a slice as not needing runtime
checking, which is immediately useful for _sizes arrays.
This fixes cgtest03, which was previously failing to compile because
the _sizes array for one of the constants in it contained a runtime
check and thus wasn't itself constant. I've added a testcase file for
the relevant bit of code.
This changes the Traversal API to the one that I've been working on in
the Polyplate branch, but implemented in terms of Data. The
performance isn't as good as the Polyplate version, but the code is a
lot simpler because it doesn't need all the type constraints (and it
doesn't make GHC struggle).
This also reworks all the passes in Tock to use the new API, including
those that previously used makeGeneric (which I've now removed) or
everywhereM. Most of the passes are simpler because of this, and I
suspect it's fixed a few subtle bugs resulting from missing recursion
in makeGeneric code.
I haven't yet profiled this, but subjectively it seems about the same
as the old Traversal (and thus faster for all the passes that didn't
yet use it).
Function returns are done in Rain by assigning to the function name, so we need a bit of extra code when checking assignments to see if the LHS is a function name.
The new behaviour is to check that both sides of a dyadic operator have the same type. This means that multiplying time by a scalar is no longer possible, but it also means (due to the lack of checks after unification) that multiplying two lists is possible, or concatenating two integers. This needs to be fixed by adding another pass.
Instead of storing the Constr, which was messy, we now store a String (to allow comparison of constructor types during unification) and a function to reform the type at the end of the type checking.
As part of this patch I also had to provide a Data instance for TypeExp (to allow CompState to still be an instance of Data). Using IORefs is easier than STRef RealWorld, and puts everything in terms of IO (which is already in PassM) rather than ST (which would require more lifting).
This patch hides all the old typeOfExpression, typeOfName, typeOfVariable, etc, and unifies them into a single type-class with an "astTypeOf" function. The type-class is currently named Typed, but that can easily be changed (it's only explicitly referred to in the Types module). The patch is essentially the type-class with a giant find-and-replace on the other modules.
The types get hairier, but the code is much simpler!
I've left {check,apply}DepthM{,2} there for now, but reimplemented them in
terms of the new combinators.
Fixes#58.
