[cfe-dev] AST transformations

[Chris Lattner]

On Apr 24, 2008, at 3:29 AM, Stephan Creutz wrote:
> for a project of mine I need to do a lot of AST transformations
> (inserting new nodes and changing existing ones), thus using the
> Rewriter for this task seems not suitable to me because after each
> transformation step I would need to rebuild the whole AST.
>
> Transformation of ASTs seems not to be trivial because AST nodes are  
> not
> changeable and recreating all nodes from scratch is not practical. I'm
> curious why it is not possible to change AST nodes, is there any
> specific reason? Or isn't it just done yet because there is no  
> interest
> in that right now?

I'm not sure what you mean here.  The ObjC rewriter does certainly  
replace subexpressions and rebuilds the AST as it goes.  For a simple  
example, see how it handles the @encode (ObjCEncodeExpr) expression.   
The objc rewriter also correctly handles recursively nested  
expressions.  See test/Rewriter/objc-ivar-receiver-1.m for an example.

-Chris