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/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author Paul Phillips
package ast
import PartialFunction._
import symtab.Flags
import scala.language.implicitConversions
/** A DSL for generating scala code. The goal is that the
* code generating code should look a lot like the code it
* generates.
trait TreeDSL {
val global: Global
import global._
import definitions._
object CODE {
// Add a null check to a Tree => Tree function
def nullSafe[T](f: Tree => Tree, ifNull: Tree): Tree => Tree =
tree => IF (tree MEMBER_== NULL) THEN ifNull ELSE f(tree)
def returning[T](x: T)(f: T => Unit): T = util.returning(x)(f)
object LIT extends (Any => Literal) {
def typed(x: Any) = apply(x) setType ConstantType(Constant(x))
def apply(x: Any) = Literal(Constant(x))
def unapply(x: Any) = condOpt(x) { case Literal(Constant(value)) => value }
// Boring, predictable trees.
def TRUE = LIT typed true
def FALSE = LIT typed false
def ZERO = LIT(0)
def NULL = LIT(null)
def UNIT = LIT(())
object WILD {
def empty = Ident(nme.WILDCARD)
def apply(tpe: Type) = Ident(nme.WILDCARD) setType tpe
def unapply(other: Any) = cond(other) { case Ident(nme.WILDCARD) => true }
def fn(lhs: Tree, op: Name, args: Tree*) = Apply(Select(lhs, op), args.toList)
def fn(lhs: Tree, op: Symbol, args: Tree*) = Apply(Select(lhs, op), args.toList)
class TreeMethods(target: Tree) {
/** logical/comparison ops **/
def OR(other: Tree) =
if (target == EmptyTree) other
else if (other == EmptyTree) target
else gen.mkOr(target, other)
def AND(other: Tree) =
if (target == EmptyTree) other
else if (other == EmptyTree) target
else gen.mkAnd(target, other)
/** Note - calling ANY_== in the matcher caused primitives to get boxed
* for the comparison, whereas looking up nme.EQ does not. See #3570 for
* an example of how target.tpe can be non-null, yet it claims not to have
* a member called nme.EQ. Not sure if that should happen, but we can be
* robust by dragging in Any regardless.
def MEMBER_== (other: Tree) = {
val opSym = if (target.tpe == null) NoSymbol else target.tpe member nme.EQ
if (opSym == NoSymbol) ANY_==(other)
else fn(target, opSym, other)
def ANY_EQ (other: Tree) = OBJ_EQ(other AS ObjectClass.tpe)
def ANY_== (other: Tree) = fn(target, Any_==, other)
def ANY_!= (other: Tree) = fn(target, Any_!=, other)
def OBJ_!= (other: Tree) = fn(target, Object_!=, other)
def OBJ_EQ (other: Tree) = fn(target, Object_eq, other)
def OBJ_NE (other: Tree) = fn(target, Object_ne, other)
def INT_>= (other: Tree) = fn(target, getMember(IntClass, nme.GE), other)
def INT_== (other: Tree) = fn(target, getMember(IntClass, nme.EQ), other)
// generic operations on ByteClass, IntClass, LongClass
def GEN_| (other: Tree, kind: ClassSymbol) = fn(target, getMember(kind, nme.OR), other)
def GEN_& (other: Tree, kind: ClassSymbol) = fn(target, getMember(kind, nme.AND), other)
def GEN_== (other: Tree, kind: ClassSymbol) = fn(target, getMember(kind, nme.EQ), other)
def GEN_!= (other: Tree, kind: ClassSymbol) = fn(target, getMember(kind, nme.NE), other)
/** Apply, Select, Match **/
def APPLY(params: Tree*) = Apply(target, params.toList)
def APPLY(params: List[Tree]) = Apply(target, params)
def MATCH(cases: CaseDef*) = Match(target, cases.toList)
def DOT(member: Name) = SelectStart(Select(target, member))
def DOT(sym: Symbol) = SelectStart(Select(target, sym))
/** Assignment */
// !!! This method is responsible for some tree sharing, but a diligent
// reviewer pointed out that we shouldn't blindly duplicate these trees
// as there might be DefTrees nested beneath them. It's not entirely
// clear how to proceed, so for now it retains the non-duplicating behavior.
def ===(rhs: Tree) = Assign(target, rhs)
/** Methods for sequences **/
def DROP(count: Int): Tree =
if (count == 0) target
else (target DOT nme.drop)(LIT(count))
/** Casting & type tests -- working our way toward understanding exactly
* what differs between the different forms of IS and AS.
* See ticket #2168 for one illustration of AS vs. AS_ANY.
def AS(tpe: Type) = gen.mkAsInstanceOf(target, tpe, any = true, wrapInApply = false)
def IS(tpe: Type) = gen.mkIsInstanceOf(target, tpe, true)
def IS_OBJ(tpe: Type) = gen.mkIsInstanceOf(target, tpe, false)
def TOSTRING() = fn(target, nme.toString_)
def GETCLASS() = fn(target, Object_getClass)
case class SelectStart(tree: Select) {
def apply(args: Tree*) = Apply(tree, args.toList)
class CaseStart(pat: Tree, guard: Tree) {
def IF(g: Tree): CaseStart = new CaseStart(pat, g)
def ==>(body: Tree): CaseDef = CaseDef(pat, guard, body)
/** VODD, if it's not obvious, means ValOrDefDef. This is the
* common code between a tree based on a pre-existing symbol and
* one being built from scratch.
trait VODDStart {
def name: Name
def defaultMods: Modifiers
def defaultTpt: Tree
def defaultPos: Position
type ResultTreeType <: ValOrDefDef
def mkTree(rhs: Tree): ResultTreeType
def ===(rhs: Tree): ResultTreeType
private var _tpt: Tree = null
private var _pos: Position = null
def withType(tp: Type): this.type = {
_tpt = TypeTree(tp)
def withPos(pos: Position): this.type = {
_pos = pos
final def mods = defaultMods
final def tpt = if (_tpt == null) defaultTpt else _tpt
final def pos = if (_pos == null) defaultPos else _pos
trait SymVODDStart extends VODDStart {
def sym: Symbol
def symType: Type
def name =
def defaultMods = Modifiers(sym.flags)
def defaultTpt = TypeTree(symType) setPos sym.pos.focus
def defaultPos = sym.pos
final def ===(rhs: Tree): ResultTreeType =
atPos(pos)(mkTree(rhs) setSymbol sym)
trait ValCreator {
self: VODDStart =>
type ResultTreeType = ValDef
def mkTree(rhs: Tree): ValDef = ValDef(mods, name.toTermName, tpt, rhs)
trait DefCreator {
self: VODDStart =>
def tparams: List[TypeDef]
def vparamss: List[List[ValDef]]
type ResultTreeType = DefDef
def mkTree(rhs: Tree): DefDef = DefDef(mods, name, tparams, vparamss, tpt, rhs)
class DefSymStart(val sym: Symbol) extends SymVODDStart with DefCreator {
def symType = sym.tpe.finalResultType
def tparams = sym.typeParams map TypeDef
def vparamss = mapParamss(sym)(ValDef)
class ValSymStart(val sym: Symbol) extends SymVODDStart with ValCreator {
def symType = sym.tpe
trait TreeVODDStart extends VODDStart {
def defaultMods = NoMods
def defaultTpt = TypeTree()
def defaultPos = NoPosition
final def ===(rhs: Tree): ResultTreeType =
if (pos == NoPosition) mkTree(rhs)
else atPos(pos)(mkTree(rhs))
class ValTreeStart(val name: Name) extends TreeVODDStart with ValCreator {
class DefTreeStart(val name: Name) extends TreeVODDStart with DefCreator {
def tparams: List[TypeDef] = Nil
def vparamss: List[List[ValDef]] = ListOfNil
class IfStart(cond: Tree, thenp: Tree) {
def THEN(x: Tree) = new IfStart(cond, x)
def ELSE(elsep: Tree) = If(cond, thenp, elsep)
def ENDIF = If(cond, thenp, EmptyTree)
class TryStart(body: Tree, catches: List[CaseDef], fin: Tree) {
def CATCH(xs: CaseDef*) = new TryStart(body, xs.toList, fin)
def ENDTRY = Try(body, catches, fin)
def CASE(pat: Tree): CaseStart = new CaseStart(pat, EmptyTree)
def DEFAULT: CaseStart = new CaseStart(WILD.empty, EmptyTree)
class SymbolMethods(target: Symbol) {
def IS_NULL() = REF(target) OBJ_EQ NULL
def GET() = fn(REF(target), nme.get)
def ARGS = target.paramss.head
/** Top level accessible. */
def MATCHERROR(arg: Tree) = Throw(MatchErrorClass.tpe, arg)
def THROW(sym: Symbol, msg: Tree): Throw = Throw(sym.tpe, msg.TOSTRING())
def NEW(tpt: Tree, args: Tree*): Tree = New(tpt, List(args.toList))
def DEF(sym: Symbol): DefSymStart = new DefSymStart(sym)
def VAL(sym: Symbol): ValSymStart = new ValSymStart(sym)
def AND(guards: Tree*) =
if (guards.isEmpty) EmptyTree
else guards reduceLeft gen.mkAnd
def IF(tree: Tree) = new IfStart(tree, EmptyTree)
def TRY(tree: Tree) = new TryStart(tree, Nil, EmptyTree)
def BLOCK(xs: Tree*) = Block(xs.init.toList, xs.last)
def NOT(tree: Tree) = Select(tree, Boolean_not)
def SOME(xs: Tree*) = Apply(SomeClass.companionSymbol, makeTupleTerm(xs.toList, true))
/** Typed trees from symbols. */
def THIS(sym: Symbol) = gen.mkAttributedThis(sym)
def ID(sym: Symbol) = gen.mkAttributedIdent(sym)
def REF(sym: Symbol) = gen.mkAttributedRef(sym)
def REF(pre: Type, sym: Symbol) = gen.mkAttributedRef(pre, sym)
def makeTupleTerm(trees: List[Tree], flattenUnary: Boolean): Tree = trees match {
case Nil => UNIT
case List(tree) if flattenUnary => tree
case _ => Apply(TupleClass(trees.length).companionModule, trees: _*)
/** Implicits - some of these should probably disappear **/
implicit def mkTreeMethods(target: Tree): TreeMethods = new TreeMethods(target)
implicit def mkTreeMethodsFromSymbol(target: Symbol): TreeMethods = new TreeMethods(Ident(target))
implicit def mkSymbolMethodsFromSymbol(target: Symbol): SymbolMethods = new SymbolMethods(target)
/** (foo DOT bar) might be simply a Select, but more likely it is to be immediately
* followed by an Apply. We don't want to add an actual apply method to arbitrary
* trees, so SelectStart is created with an apply - and if apply is not the next
* thing called, the implicit from SelectStart -> Tree will provide the tree.
implicit def mkTreeFromSelectStart(ss: SelectStart): Select = ss.tree
implicit def mkTreeMethodsFromSelectStart(ss: SelectStart): TreeMethods = mkTreeMethods(ss.tree)
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