Alternatives of patterns.

Eliminated by compiler phases Eliminated by compiler phases patmat (in the new pattern matcher of 2.10) or explicitouter (in the old pre-2.10 pattern matcher), except for occurrences in encoded Switch stmt (i.e. remaining Match(CaseDef(...)))

An extractor class to create and pattern match with syntax Alternative(trees). This AST node corresponds to the following Scala code:

pat1 | ... | patn

A tree that has an annotation attached to it. Only used for annotated types and annotation ascriptions, annotations on definitions are stored in the Modifiers. Eliminated by typechecker (typedAnnotated), the annotations are then stored in an AnnotatedType.

An extractor class to create and pattern match with syntax Annotated(annot, arg). This AST node corresponds to the following Scala code:

arg @annot // for types arg: @annot // for exprs

An extractor class to create and pattern match with syntax AppliedTypeTree(tpt, args). This AST node corresponds to the following Scala code:

tpt[args]

Should only be used with tpt nodes which are types, i.e. which have isType returning true. Otherwise TypeApply should be used instead.

List[Int] as in val x: List[Int] = ??? // represented as AppliedTypeTree(Ident(<List>), List(TypeTree(<Int>)))

def foo[T] = ??? foo[Int] // represented as TypeApply(Ident(<foo>), List(TypeTree(<Int>)))

An extractor class to create and pattern match with syntax Apply(fun, args). This AST node corresponds to the following Scala code:

fun(args)

For instance:

fun[targs](args)

Is expressed as:

Apply(TypeApply(fun, targs), args)

An extractor class to create and pattern match with syntax Assign(lhs, rhs). This AST node corresponds to the following Scala code:

lhs = rhs

Bind a variable to a rhs pattern.

Eliminated by compiler phases patmat (in the new pattern matcher of 2.10) or explicitouter (in the old pre-2.10 pattern matcher).

An extractor class to create and pattern match with syntax Bind(name, body). This AST node corresponds to the following Scala code:

pat*

An extractor class to create and pattern match with syntax Block(stats, expr). This AST node corresponds to the following Scala code:

{ stats; expr }

If the block is empty, the expr is set to Literal(Constant(())).

Case clause in a pattern match. (except for occurrences in switch statements). Eliminated by compiler phases patmat (in the new pattern matcher of 2.10) or explicitouter (in the old pre-2.10 pattern matcher)

An extractor class to create and pattern match with syntax CaseDef(pat, guard, body). This AST node corresponds to the following Scala code:

case pat if guard => body

If the guard is not present, the guard is set to EmptyTree. If the body is not specified, the body is set to Literal(Constant(()))

An extractor class to create and pattern match with syntax ClassDef(mods, name, tparams, impl). This AST node corresponds to the following Scala code:

mods class name [tparams] impl

Where impl stands for:

extends parents { defs }

Intersection type <parent1> with ... with <parentN> { <decls> }, eliminated by RefCheck

An extractor class to create and pattern match with syntax CompoundTypeTree(templ). This AST node corresponds to the following Scala code:

parent1 with ... with parentN { refinement }

An extractor class to create and pattern match with syntax DefDef(mods, name, tparams, vparamss, tpt, rhs). This AST node corresponds to the following Scala code:

mods def name[tparams](vparams_1)...(vparams_n): tpt = rhs

If the return type is not specified explicitly (i.e. is meant to be inferred), this is expressed by having tpt set to TypeTree() (but not to an EmptyTree!).

An extractor class to create and pattern match with syntax ExistentialTypeTree(tpt, whereClauses). This AST node corresponds to the following Scala code:

tpt forSome { whereClauses }

An extractor class to create and pattern match with syntax Function(vparams, body). This AST node corresponds to the following Scala code:

vparams => body

The symbol of a Function is a synthetic TermSymbol. It is the owner of the function's parameters.

An extractor class to create and pattern match with syntax Ident(qual, name). This AST node corresponds to the following Scala code:

name

Type checker converts idents that refer to enclosing fields or methods to selects. For example, name ==> this.name

An extractor class to create and pattern match with syntax If(cond, thenp, elsep). This AST node corresponds to the following Scala code:

if (cond) thenp else elsep

If the alternative is not present, the elsep is set to Literal(Constant(())).

An extractor class to create and pattern match with syntax Import(expr, selectors). This AST node corresponds to the following Scala code:

import expr.{selectors}

Selectors are a list of ImportSelectors, which conceptually are pairs of names (from, to). The last (and maybe only name) may be a nme.WILDCARD. For instance:

import qual.{w => _, x, y => z, _}

Would be represented as:

Import(qual, List(("w", WILDCARD), ("x", "x"), ("y", "z"), (WILDCARD, null)))

The symbol of an Import is an import symbol @see Symbol.newImport. It's used primarily as a marker to check that the import has been typechecked.

Import selector (not a tree, but a component of the Import tree)

Representation of an imported name its optional rename and their optional positions

Eliminated by typecheck.

An extractor class to create and pattern match with syntax ImportSelector(name, namePos, rename, renamePos). This is not an AST node, it is used as a part of the Import node.

A labelled expression. Not expressible in language syntax, but generated by the compiler to simulate while/do-while loops, and also by the pattern matcher.

The label acts much like a nested function, where params represents the incoming parameters. The symbol given to the LabelDef should have a MethodType, as if it were a nested function.

Jumps are apply nodes attributed with a label's symbol. The arguments from the apply node will be passed to the label and assigned to the Idents.

Forward jumps within a block are allowed.

An extractor class to create and pattern match with syntax LabelDef(name, params, rhs).

This AST node does not have direct correspondence to Scala code. It is used for tailcalls and like. For example, while/do are desugared to label defs as follows:

while (cond) body ==> LabelDef($L, List(), if (cond) { body; L$() } else ())

do body while (cond) ==> LabelDef($L, List(), body; if (cond) L$() else ())

An extractor class to create and pattern match with syntax Literal(value). This AST node corresponds to the following Scala code:

value

- Pattern matching expression (before compiler phase explicitouter before 2.10 / patmat from 2.10)

• Switch statements (after compiler phase explicitouter before 2.10 / patmat from 2.10)

After compiler phase explicitouter before 2.10 / patmat from 2.10, cases will satisfy the following constraints:

• all guards are EmptyTree,
• all patterns will be either Literal(Constant(x:Int)) or Alternative(lit|...|lit)
• except for an "otherwise" branch, which has pattern Ident(nme.WILDCARD)

An extractor class to create and pattern match with syntax Match(selector, cases). This AST node corresponds to the following Scala code:

selector match { cases }

Match is also used in pattern matching assignments like val (foo, bar) = baz.

An extractor class to create and pattern match with syntax Modifiers(flags, privateWithin, annotations). Modifiers encapsulate flags, visibility annotations and Scala annotations for member definitions.

An object definition, e.g. object Foo. Internally, objects are quite frequently called modules to reduce ambiguity. Eliminated by compiler phase refcheck.

An extractor class to create and pattern match with syntax ModuleDef(mods, name, impl). This AST node corresponds to the following Scala code:

mods object name impl

Where impl stands for:

extends parents { defs }

A tree that carries a name, e.g. by defining it (DefTree) or by referring to it (RefTree).

Either an assignment or a named argument. Only appears in argument lists, eliminated by compiler phase typecheck (doTypedApply), resurrected by reifier.

An extractor class to create and pattern match with syntax NamedArg(lhs, rhs). This AST node corresponds to the following Scala code:

m.f(lhs = rhs)

@annotation(lhs = rhs)

An extractor class to create and pattern match with syntax New(tpt). This AST node corresponds to the following Scala code:

new T

This node always occurs in the following context:

(new tpt).<init>[targs](args)

For example, an AST representation of:

new Example[Int](2)(3)

is the following code:

Apply( Apply( TypeApply( Select(New(TypeTree(typeOf[Example])), nme.CONSTRUCTOR) TypeTree(typeOf[Int])), List(Literal(Constant(2)))), List(Literal(Constant(3))))

An extractor class to create and pattern match with syntax PackageDef(pid, stats). This AST node corresponds to the following Scala code:

package pid { stats }

A tree which references a symbol-carrying entity. References one, as opposed to defining one; definitions are in DefTrees.

An extractor class to create and pattern match with syntax RefTree(qual, name). This AST node corresponds to either Ident, Select or SelectFromTypeTree.

An extractor class to create and pattern match with syntax Return(expr). This AST node corresponds to the following Scala code:

return expr

The symbol of a Return node is the enclosing method.

A member selection <qualifier> . <name>

An extractor class to create and pattern match with syntax Select(qual, name). This AST node corresponds to the following Scala code:

qualifier.selector

Should only be used with qualifier nodes which are terms, i.e. which have isTerm returning true. Otherwise SelectFromTypeTree should be used instead.

foo.Bar // represented as Select(Ident(<foo>), <Bar>) Foo#Bar // represented as SelectFromTypeTree(Ident(<Foo>), <Bar>)

An extractor class to create and pattern match with syntax SelectFromTypeTree(qualifier, name). This AST node corresponds to the following Scala code:

qualifier # selector

Note: a path-dependent type p.T is expressed as p.type # T

Should only be used with qualifier nodes which are types, i.e. which have isType returning true. Otherwise Select should be used instead.

Foo#Bar // represented as SelectFromTypeTree(Ident(<Foo>), <Bar>) foo.Bar // represented as Select(Ident(<foo>), <Bar>)

An extractor class to create and pattern match with syntax SingletonTypeTree(ref). This AST node corresponds to the following Scala code:

ref.type

Repetition of pattern.

Eliminated by compiler phases patmat (in the new pattern matcher of 2.10) or explicitouter (in the old pre-2.10 pattern matcher).

An extractor class to create and pattern match with syntax Star(elem). This AST node corresponds to the following Scala code:

pat*

Super reference, where qual is the corresponding this reference. A super reference C.super[M] is represented as Super(This(C), M).

An extractor class to create and pattern match with syntax Super(qual, mix). This AST node corresponds to the following Scala code:

C.super[M]

Which is represented as:

Super(This(C), M)

If mix is empty, it is tpnme.EMPTY.

The symbol of a Super is the class _from_ which the super reference is made. For instance in C.super(...), it would be C.

A tree that carries a symbol, e.g. by defining it (DefTree) or by referring to it (RefTree). Such trees start their life naked, returning NoSymbol, but after being typechecked without errors they hold non-empty symbols.

An extractor class to create and pattern match with syntax Template(parents, self, body). This AST node corresponds to the following Scala code:

extends parents { self => body }

In case when the self-type annotation is missing, it is represented as an empty value definition with nme.WILDCARD as name and NoType as type.

The symbol of a template is a local dummy. @see Symbol.newLocalDummy The owner of the local dummy is the enclosing trait or class. The local dummy is itself the owner of any local blocks. For example:

class C { def foo { // owner is C def bar // owner is local dummy } }

A tree for a term. Not all trees representing terms are TermTrees; use isTerm to reliably identify terms.

An extractor class to create and pattern match with syntax This(qual). This AST node corresponds to the following Scala code:

qual.this

The symbol of a This is the class to which the this refers. For instance in C.this, it would be C.

An extractor class to create and pattern match with syntax Throw(expr). This AST node corresponds to the following Scala code:

throw expr

The API that all trees support. The main source of information about trees is the scala.reflect.api.Trees page.

An extractor class to create and pattern match with syntax Try(block, catches, finalizer). This AST node corresponds to the following Scala code:

try block catch { catches } finally finalizer

If the finalizer is not present, the finalizer is set to EmptyTree.

A tree for a type. Not all trees representing types are TypTrees; use isType to reliably identify types.

An extractor class to create and pattern match with syntax TypeApply(fun, args). This AST node corresponds to the following Scala code:

fun[args]

Should only be used with fun nodes which are terms, i.e. which have isTerm returning true. Otherwise AppliedTypeTree should be used instead.

def foo[T] = ??? foo[Int] // represented as TypeApply(Ident(<foo>), List(TypeTree(<Int>)))

List[Int] as in val x: List[Int] = ??? // represented as AppliedTypeTree(Ident(<List>), List(TypeTree(<Int>)))

An extractor class to create and pattern match with syntax TypeBoundsTree(lo, hi). This AST node corresponds to the following Scala code:

>: lo <: hi

An abstract type, a type parameter, or a type alias. Eliminated by erasure.

An extractor class to create and pattern match with syntax TypeDef(mods, name, tparams, rhs). This AST node corresponds to the following Scala code:

mods type name[tparams] = rhs

mods type name[tparams] >: lo <: hi

First usage illustrates TypeDefs representing type aliases and type parameters. Second usage illustrates TypeDefs representing abstract types, where lo and hi are both TypeBoundsTrees and Modifier.deferred is set in mods.

A synthetic tree holding an arbitrary type. Not to be confused with with TypTree, the trait for trees that are only used for type trees. TypeTree's are inserted in several places, but most notably in RefCheck, where the arbitrary type trees are all replaced by TypeTree's.

An extractor class to create and pattern match with syntax TypeTree(). This AST node does not have direct correspondence to Scala code, and is emitted by everywhere when we want to wrap a Type in a Tree.

An extractor class to create and pattern match with syntax Typed(expr, tpt). This AST node corresponds to the following Scala code:

expr: tpt

Used to represent unapply methods in pattern matching.

For example:

2 match { case Foo(x) => x }

Is represented as:

Match(
  Literal(Constant(2)),
  List(
    CaseDef(
      UnApply(
        // a dummy node that carries the type of unapplication to patmat
        // the <unapply-selector> here doesn't have an underlying symbol
        // it only has a type assigned, therefore after `untypecheck` this tree is no longer typeable
        Apply(Select(Ident(Foo), TermName("unapply")), List(Ident(TermName("<unapply-selector>")))),
        // arguments of the unapply => nothing synthetic here
        List(Bind(TermName("x"), Ident(nme.WILDCARD)))),
      EmptyTree,
      Ident(TermName("x")))))

Introduced by typer. Eliminated by compiler phases patmat (in the new pattern matcher of 2.10) or explicitouter (in the old pre-2.10 pattern matcher).

An extractor class to create and pattern match with syntax UnApply(fun, args). This AST node does not have direct correspondence to Scala code, and is introduced when typechecking pattern matches and try blocks.

Broadly speaking, a value definition. All these are encoded as ValDefs:

• immutable values, e.g. "val x"
• mutable values, e.g. "var x" - the MUTABLE flag set in mods
• lazy values, e.g. "lazy val x" - the LAZY flag set in mods
• method parameters, see vparamss in scala.reflect.api.Trees#DefDef - the PARAM flag is set in mods
• explicit self-types, e.g. class A { self: Bar => }

An extractor class to create and pattern match with syntax ValDef(mods, name, tpt, rhs). This AST node corresponds to any of the following Scala code:

mods val name: tpt = rhs

mods var name: tpt = rhs

mods name: tpt = rhs // in signatures of function and method definitions

self: Bar => // self-types

If the type of a value is not specified explicitly (i.e. is meant to be inferred), this is expressed by having tpt set to TypeTree() (but not to an EmptyTree!).