AST traversal

I was a bit stuck on how to traverse the AST. Since each node is an object with named fields (instead of elements in a “children” list, for instance), I would have potentially needed to write a “get children” function to iterate on them and traverse the tree. But thanks to Lua’s dynamism, I made only one function at AbstractNode level, that goes through all members of the table (since Lua objects are tables) and gather everything that looks like an AbstractNode. It also goes through lists and get nodes there too. For instance the Block object has a list of statements. Magic. And it’s not too slow, for now.

Now once that is plugged to the pass system, I can have something fun like:

SoolAnalyzer:add_pass( Pass('lol','top-down') )

function AbstractNode:lol(a)
    if self.node then
        a:add_info(classname(self.class),self.node:position())
    end
end

The analyzer is a list of passes, applied one by one to the tree. Each pass has a “name”, which is simply the name of a method to call on each node (if it answers to it). It also passes itself as argument, for error collecting. This example pass simply goes through all nodes, and reports their name and position as an information diagnostic. On a short example, it produces this:

Compiler info: successfully lexed file example.sool for a total of 50 tokens
Compiler info: successfully parsed file example.sool
analyzer info: example.sool:1-15: Class
class MyClass

    meth str dothat([num] n, {sym,Class} c)

        b = a + (10 * 20)
        for i,v in [1,2,3] do
            if v then
                break
            end
        end

        return lol
    end

end
analyzer info: example.sool:3-13: Method
    meth str dothat([num] n, {sym,Class} c)

        b = a + (10 * 20)
        for i,v in [1,2,3] do
            if v then
                break
            end
        end

        return lol
    end
analyzer info: example.sool:3: Argument
    meth str dothat([num] n, {sym,Class} c)
                    ^^^^^^^                 
analyzer info: example.sool:3: ArrayType
    meth str dothat([num] n, {sym,Class} c)
                    ^^^^^                   
analyzer info: example.sool:3: NumberType
    meth str dothat([num] n, {sym,Class} c)
                     ^^^                    
analyzer info: example.sool:3: Argument
    meth str dothat([num] n, {sym,Class} c)
                             ^^^^^^^^^^^^^  
analyzer info: example.sool:3: TableType
    meth str dothat([num] n, {sym,Class} c)
                             ^^^^^^^^^^^    
analyzer info: example.sool:3: SymbolType
    meth str dothat([num] n, {sym,Class} c)
                              ^^^           
analyzer info: example.sool:3: ClassType
    meth str dothat([num] n, {sym,Class} c)
                                  ^^^^^     
analyzer info: example.sool:3: StringType
    meth str dothat([num] n, {sym,Class} c)
         ^^^                                
analyzer info: example.sool:5-12: Block
        b = a + (10 * 20)
        for i,v in [1,2,3] do
            if v then
                break
            end
        end

        return lol
analyzer info: example.sool:5: Assignment
        b = a + (10 * 20)
        ^^^^^^^^^^^^^^^^^ 
analyzer info: example.sool:5: BinaryOperation
        b = a + (10 * 20)
            ^^^^^^^^^^^^^ 
analyzer info: example.sool:5: BinaryOperation
        b = a + (10 * 20)
                ^^^^^^^^^ 
analyzer info: example.sool:5: AtomicNumber
        b = a + (10 * 20)
                      ^^  
analyzer info: example.sool:5: AtomicNumber
        b = a + (10 * 20)
                 ^^       
analyzer info: example.sool:5: MethodCall
        b = a + (10 * 20)
            ^             
analyzer info: example.sool:5: MethodCall
        b = a + (10 * 20)
        ^                 
analyzer info: example.sool:6-10: For
        for i,v in [1,2,3] do
            if v then
                break
            end
        end
analyzer info: example.sool:7-9: Block
            if v then
                break
            end
analyzer info: example.sool:7-9: If
            if v then
                break
            end
analyzer info: example.sool:7: MethodCall
            if v then
               ^      
analyzer info: example.sool:8: Block
                break
                ^^^^^ 
analyzer info: example.sool:8: Break
                break
                ^^^^^ 
analyzer info: example.sool:6: ArrayCons
        for i,v in [1,2,3] do
                   ^^^^^^^    
analyzer info: example.sool:6: AtomicNumber
        for i,v in [1,2,3] do
                    ^         
analyzer info: example.sool:6: AtomicNumber
        for i,v in [1,2,3] do
                      ^       
analyzer info: example.sool:6: AtomicNumber
        for i,v in [1,2,3] do
                        ^     
analyzer info: example.sool:12: Return
        return lol
        ^^^^^^^^^^ 
analyzer info: example.sool:12: MethodCall
        return lol
               ^^^ 
Compiler info: chunk passed validation, for a total of 1 classes

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