Velocity compiler again

I postes a while ago about my Velocity "compiler". There is another interesting problem in it: How do you handle internal macros?. In Velocity you can define macros which are pieces of reusable code. The problem is how do you translate that into a java class ? The solution would be something like a method call obviously (this is what I use right but it might be something totally different). But with a method call you have the typing problem :-).

You start from this:

#macro( macroName $macroParam1 $macroParam1);
## macro code here
#end

## and a macro call here
#macroName( $actualParam1, $actualParam2 );

and you should end up with something like:

protected void macroName(Type1 macroParam1, Type2 macroParam2) {
// function code translated from macro here.
}

// and a call here
macroName(actualParam1, actualParam2);

The problem is: how do you find out the Type1, Type2 parameter types?. It turns out that there are two approaces. Infer the type from actual calls and infer the type from the actual macro code. I haven't really thought about the latter so I will talk mostly about the first one.

I used this because i already had some code helping me do it. I used it to infer the type of an expression in a #set( $var = $value); statement in order to properly convert it InferredType var = value; statement. So what i ended up doing is this:
- visit the AST tree of the velocity macro
- do the translation for all the nodes which are not ASTDirective with the name of macro (this is how an internal macro is presented in a velocity macro).
- for every node not translated i'm putting in a queue and remember it for later.
- while processing the other nodes i look for callers of macros.
  - I infer the types for any parameters passed to the macro and keep them in a map in the generator.
- after the processing is completed I iterate the macros and build them as functions using the parameters types inferred earlier.

This one works reasonably well in most of the cases however there are cases in which it fails :-). It should be visible from the algorithm description and the solution to this problem too ..

Mihai.