The previous method, using the C preprocessor was both nasty, and crazily resource-intensive. The new method stores stack size information in files that are read in and processed by the compiler when it comes time to link.
They are now recursed into with no type context, then afterwards the type is deduced. This seems to be how they were meant to work, and is also much faster than what I was doing.
This patch follows on from the previous change to the parser. When it spots a function-call, it looks for operators and treats them differently.
It keeps a stack of operators in scope (csOperators in CompState), and when an operator is used, it searches the stack (with all old definitions masked out) for operator definitions to resolve to.
The way it chooses which operator to use in the presence of overloadings (e.g. + on INT vs + on INT32) is simply to try them all. If one matches, it uses that. If none, or more than one match, it gives an error. This makes the code simple and seems logical, but I'm not totally confident if this is the required behaviour for resolving overloaded operators.
The idea behind this is to parse unary/binary operators into function calls with 1/2 operands. So the AST actually has a FunctionCall with the name "+". Function names may now be quoted operators, and thus you can also have function declarations with names such as "+". Resolving is *not* done in the parser for these function names, but rather every "+" is left as "+" (no matter what types it operates on, or what is in scope) by the parser (see later patches to InferTypes instead).
When parsing an occam source file, we automatically insert a bunch of PRAGMA TOCKEXTERNAL that define the default occam operators (e.g. + on INT) as external C functions (which they are!). The naming scheme for these C functions is standardised, and must be used by functions such as mulExprs (which bases the function on the type of its operands) and the new versions mulExprsInt (which are pegged to INT).
The Types module also has some new functions for dealing with operator-functions.
This is the first part of a change, suggested in #64, to remove operators in favour of functions (which will also allow user-defined operators).
The ticket suggested removed operators after the parser, but the way it's working out, it is fine to just never represent as anything other than function calls.
All the knock-on changes will be recorded in later patches.
