Scala AST reference

General notes

• All the types (say X) should be prefixed by global.X when used in a case statement.

• Type names (like Int, Map, etc) either belong to a class called TypeName_S or TypeName_R. But these are private members of the class Names so we cannot pattern match against them. However, any AST node that is a type name has the flag isTypeName set to true. This could be used to identify type names. Below, all type names are represented by the string newTypeName("<some-name>").

Types

Here are some examples.

Scala type	AST case class
Int	Ident(newTypeName("Int"))
String	Ident(newTypeName("String"))
Foo	Ident(newTypeName("Foo"))
java.util.Random	Select(Select(Ident(newTermName("java")), newTermName("util")), newTypeName("Random"))
scala.util.Random	Select(Select(Ident(newTermName("scala")), newTermName("util")), newTypeName("Random"))
Set[String]	AppliedTypeTree(Ident(newTypeName("Set")),List(Ident(newTypeName("String"))))
Map[String, Int]	AppliedTypeTree(Ident(newTypeName("Map")), List(Ident(newTypeName("String")), Ident(newTypeName("Int"))))
(String, Int)	AppliedTypeTree(Select(Ident(scala), newTypeName("Tuple2")), List(Ident(newTypeName("String")), Ident(newTypeName("Int"))))
(String, Int, Double)	AppliedTypeTree(Select(Ident(scala), newTypeName("Tuple3")), List(Ident(newTypeName("String")), Ident(newTypeName("Int")), Ident(newTypeName("Double"))))
String => Double	AppliedTypeTree(Select(Select(Ident(nme.ROOTPKG), scala), newTypeName("Function1")), List(Ident(newTypeName("String")), Ident(newTypeName("Double"))))
(String, Int) => Double	AppliedTypeTree(Select(Select(Ident(nme.ROOTPKG), scala), newTypeName("Function2")), List(Ident(newTypeName("String")), Ident(newTypeName("Int")), Ident(newTypeName("Double")))
(String, Int, Boolean) => Double	AppliedTypeTree(Select(Select(Ident(nme.ROOTPKG), scala), newTypeName("Function3")), List(Ident(newTypeName("String")), Ident(newTypeName("Int")), Ident(newTypeName("Boolean")), Ident(newTypeName("Double"))))
String => Int => Double	AppliedTypeTree(Select(Select(Ident(nme.ROOTPKG), scala), newTypeName("Function1")), List(Ident(newTypeName("String")), AppliedTypeTree(Select(Select(Ident(nme.ROOTPKG), scala), newTypeName("Function1")), List(Ident(newTypeName("Int")), Ident(newTypeName("Double"))))))

Notes

• In general, AppliedTypeTree takes two arguments. The first argument tells us about the type and the second argument is a list that gives information about the types of parameters used to construct the types.
• Select is used to pick a member of a type or an object. We will see more of this below too.
• Some Idents take the word scala as a parameter. Most likely, we won't be using this. So, for now, let's ignore them. Ditto for nme.ROOTPKG.

Creating new types

• type Person = <some-type> becomes TypeDef(name =TypeName_R("Person"), rhs = <a tree that represents the right hand side>)

The rhs tree above should be a Type tree as described in the section Types.