This may seem like an odd change, but it simplifies the logic a lot. I kept having problems with passes not operating on externals (e.g. functions-to-procs, adding array sizes, constant folding in array dimensions) and adding a special case every time to also process the externals was getting silly.
Putting the externals in the AST therefore made sense, but I didn't want to just add dummy bodies as this would cause them to throw up errors (e.g. in the type-checking for functions). So I turned the bodies into a Maybe type, and that has worked out well.
I also stopped storing the formals in csExternals (since they are now in csNames, and the tree), which streamlined that nicely, and stopped me having to keep them up to date.
When we pull up names (which happens before abbreviation checking), we create a lot of nonces with greater scope than the original variables. When we go to abbreviation check this, we therefore set off lots of false alarms about originally safe code. So to fix this, the easiest method seems to be turning off checking on all the names introduced by the compiler.
This makes cgtest82 work, although I'm not very happy with it as a fix. I'd
rather have a way of ensuring the state's definitions are kept up to date when
we change something in the AST.
This fixes the AST, parser and typechecker, and adds a pass to
transform Result back into Abbrev, but doesn't transform Initial yet.
(It actually works for trivial stuff anyway, but it won't do the right
thing for complex types or PROC parameters.)
It appears (to me) to make sense to support INITIAL/RESULT reshaping
and retyping too, so this does.
Refs #42.
