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What's the best way to recursively search for an element in scala 2.10 ASTs?

The trees might be a result of power.trees(code) or mirror.mkToolBox().parseExpr(code) Edit. In 2.10.0-RC1 parseExpr has been renamed to parse.

The concrete use-case that I have is extracting the code of a method from a given class/object code by method name, but I assume that the question would be more relevant for others if formulated in a more generic way.

Eugene Burmako
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Sagie Davidovich
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1 Answers1

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Maybe you should have a look at https://github.com/scala/scala/blob/2.10.x/src/reflect/scala/reflect/api/Trees.scala#L606, especially at the classes Traverser, Transformer and the methods for substitution (Tree.substituteSymbols, Tree.substituteTypes or Tree.substituteThis). If you want to extract a method from a tree, you can use a Traverser and override the traverse method. In the traverse method, you check whether the node matches the method you want. If so, you are done. If not, you call super.traverse.

Kim Stebel
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    The linked code is quite obsolete in comparison with trunk. Here are the correct links: 1) tree AST classes: https://github.com/scala/scala/blob/2.10.x/src/library/scala/reflect/base/Trees.scala, 2) transformers and traversers: https://github.com/scala/scala/blob/2.10.x/src/reflect/scala/reflect/api/Trees.scala#L606 – Eugene Burmako Aug 25 '12 at 16:01
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    Here's example of a transformer: https://github.com/scala/scala/blob/46d57d47e81c8794a9a3594e080576788cc92324/src/compiler/scala/reflect/reify/phases/Reshape.scala (the code would definitely use a cleanup, but it's too nice of an example to ignore it). Note the `super.transform` and `copyAttrs` parts. – Eugene Burmako Aug 25 '12 at 16:08
  • Also `TreeSubstituter` is not exposed in the API. Use `Tree.substituteSymbols`, `Tree.substituteTypes` or `Tree.substituteThis` where appropriate (or write your own transformer). – Eugene Burmako Aug 25 '12 at 16:10
  • Thanks for your advice, I have updated my answer accordingly. – Kim Stebel Aug 25 '12 at 16:16