Scala example source code file (TreeGen.scala)
The TreeGen.scala Scala example source codepackage scala
package reflect
package internal
import Flags._
import util._
import scala.collection.mutable.ListBuffer
abstract class TreeGen {
val global: SymbolTable
import global._
import definitions._
def rootId(name: Name) = Select(Ident(nme.ROOTPKG), name)
def rootScalaDot(name: Name) = Select(rootId(nme.scala_) setSymbol ScalaPackage, name)
def scalaDot(name: Name) = Select(Ident(nme.scala_) setSymbol ScalaPackage, name)
def scalaAnnotationDot(name: Name) = Select(scalaDot(nme.annotation), name)
def scalaAnyRefConstr = scalaDot(tpnme.AnyRef) // used in ide
def scalaFunctionConstr(argtpes: List[Tree], restpe: Tree, abstractFun: Boolean = false): Tree = {
val cls = if (abstractFun)
mkAttributedRef(AbstractFunctionClass(argtpes.length))
else
mkAttributedRef(FunctionClass(argtpes.length))
AppliedTypeTree(cls, argtpes :+ restpe)
}
/** A creator for method calls, e.g. fn[T1, T2, ...](v1, v2, ...)
* There are a number of variations.
*
* @param receiver symbol of the method receiver
* @param methodName name of the method to call
* @param targs type arguments (if Nil, no TypeApply node will be generated)
* @param args value arguments
* @return the newly created trees.
*/
def mkMethodCall(receiver: Symbol, methodName: Name, targs: List[Type], args: List[Tree]): Tree =
mkMethodCall(Select(mkAttributedRef(receiver), methodName), targs, args)
def mkMethodCall(method: Symbol, targs: List[Type], args: List[Tree]): Tree =
mkMethodCall(mkAttributedRef(method), targs, args)
def mkMethodCall(method: Symbol, args: List[Tree]): Tree =
mkMethodCall(method, Nil, args)
def mkMethodCall(target: Tree, args: List[Tree]): Tree =
mkMethodCall(target, Nil, args)
def mkMethodCall(receiver: Symbol, methodName: Name, args: List[Tree]): Tree =
mkMethodCall(receiver, methodName, Nil, args)
def mkMethodCall(receiver: Tree, method: Symbol, targs: List[Type], args: List[Tree]): Tree =
mkMethodCall(Select(receiver, method), targs, args)
def mkMethodCall(target: Tree, targs: List[Type], args: List[Tree]): Tree =
Apply(mkTypeApply(target, mapList(targs)(TypeTree)), args)
def mkNullaryCall(method: Symbol, targs: List[Type]): Tree =
mkTypeApply(mkAttributedRef(method), mapList(targs)(TypeTree))
/** Builds a reference to value whose type is given stable prefix.
* The type must be suitable for this. For example, it
* must not be a TypeRef pointing to an abstract type variable.
*/
def mkAttributedQualifier(tpe: Type): Tree =
mkAttributedQualifier(tpe, NoSymbol)
/** Builds a reference to value whose type is given stable prefix.
* If the type is unsuitable, e.g. it is a TypeRef for an
* abstract type variable, then an Ident will be made using
* termSym as the Ident's symbol. In that case, termSym must
* not be NoSymbol.
*/
def mkAttributedQualifier(tpe: Type, termSym: Symbol): Tree = {
def failMessage = "mkAttributedQualifier(" + tpe + ", " + termSym + ")"
tpe match {
case NoPrefix =>
EmptyTree
case ThisType(clazz) =>
if (clazz.isEffectiveRoot) EmptyTree
else mkAttributedThis(clazz)
case SingleType(pre, sym) =>
mkApplyIfNeeded(mkAttributedStableRef(pre, sym))
case TypeRef(pre, sym, args) =>
if (sym.isRoot) {
mkAttributedThis(sym)
} else if (sym.isModuleClass) {
mkApplyIfNeeded(mkAttributedRef(pre, sym.sourceModule))
} else if (sym.isModule || sym.isClass) {
assert(phase.erasedTypes, failMessage)
mkAttributedThis(sym)
} else if (sym.isType) {
assert(termSym != NoSymbol, failMessage)
mkAttributedIdent(termSym) setType tpe
} else {
mkAttributedRef(pre, sym)
}
case ConstantType(value) =>
Literal(value) setType tpe
case AnnotatedType(_, atp) =>
mkAttributedQualifier(atp)
case RefinedType(parents, _) =>
// I am unclear whether this is reachable, but
// the following implementation looks logical -Lex
val firstStable = parents.find(_.isStable)
assert(!firstStable.isEmpty, failMessage + " parents = " + parents)
mkAttributedQualifier(firstStable.get)
case _ =>
abort("bad qualifier received: " + failMessage)
}
}
/** If this is a reference to a method with an empty
* parameter list, wrap it in an apply.
*/
def mkApplyIfNeeded(qual: Tree) = qual.tpe match {
case MethodType(Nil, restpe) => atPos(qual.pos)(Apply(qual, Nil) setType restpe)
case _ => qual
}
/** Builds a reference to given symbol with given stable prefix. */
def mkAttributedRef(pre: Type, sym: Symbol): RefTree = {
val qual = mkAttributedQualifier(pre)
qual match {
case EmptyTree => mkAttributedIdent(sym)
case This(clazz) if qual.symbol.isEffectiveRoot => mkAttributedIdent(sym)
case _ => mkAttributedSelect(qual, sym)
}
}
/** Builds a reference to given symbol. */
def mkAttributedRef(sym: Symbol): RefTree =
if (sym.owner.isClass) mkAttributedRef(sym.owner.thisType, sym)
else mkAttributedIdent(sym)
def mkUnattributedRef(sym: Symbol): RefTree = mkUnattributedRef(sym.fullNameAsName('.'))
def mkUnattributedRef(fullName: Name): RefTree = {
val hd :: tl = nme.segments(fullName.toString, assumeTerm = fullName.isTermName)
tl.foldLeft(Ident(hd): RefTree)(Select(_,_))
}
/** Replaces tree type with a stable type if possible */
def stabilize(tree: Tree): Tree = stableTypeFor(tree) match {
case NoType => tree
case tp => tree setType tp
}
/** Computes stable type for a tree if possible */
def stableTypeFor(tree: Tree): Type = (
if (!treeInfo.admitsTypeSelection(tree)) NoType
else tree match {
case This(_) => ThisType(tree.symbol)
case Ident(_) => singleType(tree.symbol.owner.thisType, tree.symbol)
case Select(qual, _) => singleType(qual.tpe, tree.symbol)
case _ => NoType
}
)
/** Builds a reference with stable type to given symbol */
def mkAttributedStableRef(pre: Type, sym: Symbol): Tree =
stabilize(mkAttributedRef(pre, sym))
def mkAttributedStableRef(sym: Symbol): Tree =
stabilize(mkAttributedRef(sym))
def mkAttributedThis(sym: Symbol): This =
This(sym.name.toTypeName) setSymbol sym setType sym.thisType
def mkAttributedIdent(sym: Symbol): RefTree =
Ident(sym.name) setSymbol sym setType sym.tpeHK
def mkAttributedSelect(qual: Tree, sym: Symbol): RefTree = {
// Tests involving the repl fail without the .isEmptyPackage condition.
if (qual.symbol != null && (qual.symbol.isEffectiveRoot || qual.symbol.isEmptyPackage))
mkAttributedIdent(sym)
else {
// Have to recognize anytime a selection is made on a package
// so it can be rewritten to foo.bar.`package`.name rather than
// foo.bar.name if name is in the package object.
// TODO - factor out the common logic between this and
// the Typers method "isInPackageObject", used in typedIdent.
val qualsym = (
if (qual.tpe ne null) qual.tpe.typeSymbol
else if (qual.symbol ne null) qual.symbol
else NoSymbol
)
val needsPackageQualifier = (
(sym ne null)
&& qualsym.hasPackageFlag
&& !(sym.isDefinedInPackage || sym.moduleClass.isDefinedInPackage) // SI-7817 work around strangeness in post-flatten `Symbol#owner`
)
val pkgQualifier =
if (needsPackageQualifier) {
val packageObject = rootMirror.getPackageObjectWithMember(qual.tpe, sym)
Select(qual, nme.PACKAGE) setSymbol packageObject setType singleType(qual.tpe, packageObject)
}
else qual
val tree = Select(pkgQualifier, sym)
if (pkgQualifier.tpe == null) tree
else tree setType (qual.tpe memberType sym)
}
}
/** Builds a type application node if args.nonEmpty, returns fun otherwise. */
def mkTypeApply(fun: Tree, targs: List[Tree]): Tree =
if (targs.isEmpty) fun else TypeApply(fun, targs)
def mkAppliedTypeTree(fun: Tree, targs: List[Tree]): Tree =
if (targs.isEmpty) fun else AppliedTypeTree(fun, targs)
def mkAttributedTypeApply(target: Tree, method: Symbol, targs: List[Type]): Tree =
mkTypeApply(mkAttributedSelect(target, method), targs map TypeTree)
private def mkSingleTypeApply(value: Tree, tpe: Type, what: Symbol, wrapInApply: Boolean) = {
val tapp = mkAttributedTypeApply(value, what, tpe.dealias :: Nil)
if (wrapInApply) Apply(tapp, Nil) else tapp
}
private def typeTestSymbol(any: Boolean) = if (any) Any_isInstanceOf else Object_isInstanceOf
private def typeCastSymbol(any: Boolean) = if (any) Any_asInstanceOf else Object_asInstanceOf
/** Builds an instance test with given value and type. */
def mkIsInstanceOf(value: Tree, tpe: Type, any: Boolean = true, wrapInApply: Boolean = true): Tree =
mkSingleTypeApply(value, tpe, typeTestSymbol(any), wrapInApply)
/** Builds a cast with given value and type. */
def mkAsInstanceOf(value: Tree, tpe: Type, any: Boolean = true, wrapInApply: Boolean = true): Tree =
mkSingleTypeApply(value, tpe, typeCastSymbol(any), wrapInApply)
/** Cast `tree` to `pt`, unless tpe is a subtype of pt, or pt is Unit. */
def maybeMkAsInstanceOf(tree: Tree, pt: Type, tpe: Type, beforeRefChecks: Boolean = false): Tree =
if ((pt == UnitTpe) || (tpe <:< pt)) tree
else atPos(tree.pos)(mkAsInstanceOf(tree, pt, any = true, wrapInApply = !beforeRefChecks))
/** Apparently we smuggle a Type around as a Literal(Constant(tp))
* and the implementation of Constant#tpe is such that x.tpe becomes
* ClassType(value.asInstanceOf[Type]), i.e. java.lang.Class[Type].
* Can't find any docs on how/why it's done this way. See ticket
* SI-490 for some interesting comments from lauri alanko suggesting
* that the type given by classOf[T] is too strong and should be
* weakened so as not to suggest that classOf[List[String]] is any
* different from classOf[List[Int]].
*
* !!! See deconstMap in Erasure for one bug this encoding has induced:
* I would be very surprised if there aren't more.
*/
def mkClassOf(tp: Type): Tree =
Literal(Constant(tp)) setType ConstantType(Constant(tp))
/** Builds a list with given head and tail. */
def mkNil: Tree = mkAttributedRef(NilModule)
/** Builds a tree representing an undefined local, as in
* var x: T = _
* which is appropriate to the given Type.
*/
def mkZero(tp: Type): Tree = tp.typeSymbol match {
case NothingClass => mkMethodCall(Predef_???, Nil) setType NothingTpe
case _ => Literal(mkConstantZero(tp)) setType tp
}
def mkConstantZero(tp: Type): Constant = tp.typeSymbol match {
case UnitClass => Constant(())
case BooleanClass => Constant(false)
case FloatClass => Constant(0.0f)
case DoubleClass => Constant(0.0d)
case ByteClass => Constant(0.toByte)
case ShortClass => Constant(0.toShort)
case IntClass => Constant(0)
case LongClass => Constant(0L)
case CharClass => Constant(0.toChar)
case _ => Constant(null)
}
/** Wrap an expression in a named argument. */
def mkNamedArg(name: Name, tree: Tree): Tree = mkNamedArg(Ident(name), tree)
def mkNamedArg(lhs: Tree, rhs: Tree): Tree = atPos(rhs.pos)(AssignOrNamedArg(lhs, rhs))
/** Builds a tuple */
def mkTuple(elems: List[Tree], flattenUnary: Boolean = true): Tree = elems match {
case Nil =>
Literal(Constant(()))
case tree :: Nil if flattenUnary =>
tree
case _ =>
Apply(scalaDot(TupleClass(elems.length).name.toTermName), elems)
}
def mkTupleType(elems: List[Tree], flattenUnary: Boolean = true): Tree = elems match {
case Nil =>
scalaDot(tpnme.Unit)
case List(tree) if flattenUnary =>
tree
case _ =>
AppliedTypeTree(scalaDot(TupleClass(elems.length).name), elems)
}
// tree1 AND tree2
def mkAnd(tree1: Tree, tree2: Tree): Tree =
Apply(Select(tree1, Boolean_and), List(tree2))
// tree1 OR tree2
def mkOr(tree1: Tree, tree2: Tree): Tree =
Apply(Select(tree1, Boolean_or), List(tree2))
def mkRuntimeUniverseRef: Tree = {
assert(ReflectRuntimeUniverse != NoSymbol)
mkAttributedRef(ReflectRuntimeUniverse) setType singleType(ReflectRuntimeUniverse.owner.thisPrefix, ReflectRuntimeUniverse)
}
def mkSeqApply(arg: Tree): Apply = {
val factory = Select(mkAttributedRef(SeqModule), nme.apply)
Apply(factory, List(arg))
}
def mkSuperInitCall: Select = Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR)
/** Generates a template with constructor corresponding to
*
* constrmods (vparams1_) ... (vparams_n) preSuper { presupers }
* extends superclass(args_1) ... (args_n) with mixins { self => body }
*
* This gets translated to
*
* extends superclass with mixins { self =>
* presupers' // presupers without rhs
* vparamss // abstract fields corresponding to value parameters
* def <init>(vparamss) {
* presupers
* super.<init>(args)
* }
* body
* }
*/
def mkTemplate(parents: List[Tree], self: ValDef, constrMods: Modifiers,
vparamss: List[List[ValDef]], body: List[Tree], superPos: Position = NoPosition): Template = {
/* Add constructor to template */
// create parameters for <init> as synthetic trees.
var vparamss1 = mmap(vparamss) { vd =>
val param = atPos(vd.pos.makeTransparent) {
val mods = Modifiers(vd.mods.flags & (IMPLICIT | DEFAULTPARAM | BYNAMEPARAM) | PARAM | PARAMACCESSOR)
ValDef(mods withAnnotations vd.mods.annotations, vd.name, vd.tpt.duplicate, duplicateAndKeepPositions(vd.rhs))
}
param
}
val (edefs, rest) = body span treeInfo.isEarlyDef
val (evdefs, etdefs) = edefs partition treeInfo.isEarlyValDef
val gvdefs = evdefs map {
case vdef @ ValDef(_, _, tpt, _) =>
copyValDef(vdef)(
// atPos for the new tpt is necessary, since the original tpt might have no position
// (when missing type annotation for ValDef for example), so even though setOriginal modifies the
// position of TypeTree, it would still be NoPosition. That's what the author meant.
tpt = atPos(vdef.pos.focus)(TypeTree() setOriginal tpt setPos tpt.pos.focus),
rhs = EmptyTree
)
}
val lvdefs = evdefs collect { case vdef: ValDef => copyValDef(vdef)(mods = vdef.mods | PRESUPER) }
val constr = {
if (constrMods.isTrait) {
if (body forall treeInfo.isInterfaceMember) None
else Some(
atPos(wrappingPos(superPos, lvdefs)) (
DefDef(NoMods, nme.MIXIN_CONSTRUCTOR, Nil, ListOfNil, TypeTree(), Block(lvdefs, Literal(Constant())))))
}
else {
// convert (implicit ... ) to ()(implicit ... ) if its the only parameter section
if (vparamss1.isEmpty || !vparamss1.head.isEmpty && vparamss1.head.head.mods.isImplicit)
vparamss1 = List() :: vparamss1
val superCall = pendingSuperCall // we can't know in advance which of the parents will end up as a superclass
// this requires knowing which of the parents is a type macro and which is not
// and that's something that cannot be found out before typer
// (the type macros aren't in the trunk yet, but there is a plan for them to land there soon)
// this means that we don't know what will be the arguments of the super call
// therefore here we emit a dummy which gets populated when the template is named and typechecked
Some(
atPos(wrappingPos(superPos, lvdefs ::: vparamss1.flatten).makeTransparent) (
DefDef(constrMods, nme.CONSTRUCTOR, List(), vparamss1, TypeTree(), Block(lvdefs ::: List(superCall), Literal(Constant())))))
}
}
constr foreach (ensureNonOverlapping(_, parents ::: gvdefs, focus = false))
// Field definitions for the class - remove defaults.
val fieldDefs = vparamss.flatten map (vd => {
val field = copyValDef(vd)(mods = vd.mods &~ DEFAULTPARAM, rhs = EmptyTree)
// Prevent overlapping of `field` end's position with default argument's start position.
// This is needed for `Positions.Locator(pos).traverse` to return the correct tree when
// the `pos` is a point position with all its values equal to `vd.rhs.pos.start`.
if(field.pos.isRange && vd.rhs.pos.isRange) field.pos = field.pos.withEnd(vd.rhs.pos.start - 1)
field
})
global.Template(parents, self, gvdefs ::: fieldDefs ::: constr ++: etdefs ::: rest)
}
def mkParents(ownerMods: Modifiers, parents: List[Tree], parentPos: Position = NoPosition) =
if (ownerMods.isCase) parents ::: List(scalaDot(tpnme.Product), scalaDot(tpnme.Serializable))
else if (parents.isEmpty) atPos(parentPos)(scalaAnyRefConstr) :: Nil
else parents
def mkClassDef(mods: Modifiers, name: TypeName, tparams: List[TypeDef], templ: Template): ClassDef = {
val isInterface = mods.isTrait && (templ.body forall treeInfo.isInterfaceMember)
val mods1 = if (isInterface) (mods | Flags.INTERFACE) else mods
ClassDef(mods1, name, tparams, templ)
}
/** Create positioned tree representing an object creation <new parents { stats }
* @param npos the position of the new
* @param cpos the position of the anonymous class starting with parents
*/
def mkNew(parents: List[Tree], self: ValDef, stats: List[Tree],
npos: Position, cpos: Position): Tree =
if (parents.isEmpty)
mkNew(List(scalaAnyRefConstr), self, stats, npos, cpos)
else if (parents.tail.isEmpty && stats.isEmpty) {
// `Parsers.template` no longer differentiates tpts and their argss
// e.g. `C()` will be represented as a single tree Apply(Ident(C), Nil)
// instead of parents = Ident(C), argss = Nil as before
// this change works great for things that are actually templates
// but in this degenerate case we need to perform postprocessing
val app = treeInfo.dissectApplied(parents.head)
atPos(npos union cpos) { New(app.callee, app.argss) }
} else {
val x = tpnme.ANON_CLASS_NAME
atPos(npos union cpos) {
Block(
List(
atPos(cpos) {
ClassDef(
Modifiers(FINAL), x, Nil,
mkTemplate(parents, self, NoMods, ListOfNil, stats, cpos.focus))
}),
atPos(npos) {
New(
Ident(x) setPos npos.focus,
Nil)
}
)
}
}
/** Create a tree representing the function type (argtpes) => restpe */
def mkFunctionTypeTree(argtpes: List[Tree], restpe: Tree): Tree =
AppliedTypeTree(rootScalaDot(newTypeName("Function" + argtpes.length)), argtpes ::: List(restpe))
/** Create a literal unit tree that is inserted by the compiler but not
* written by end user. It's important to distinguish the two so that
* quasiquotes can strip synthetic ones away.
*/
def mkSyntheticUnit() = Literal(Constant(())).updateAttachment(SyntheticUnitAttachment)
/** Create block of statements `stats` */
def mkBlock(stats: List[Tree]): Tree =
if (stats.isEmpty) mkSyntheticUnit()
else if (!stats.last.isTerm) Block(stats, mkSyntheticUnit())
else if (stats.length == 1) stats.head
else Block(stats.init, stats.last)
/** Create a block that wraps multiple statements but don't
* do any wrapping if there is just one statement. Used by
* quasiquotes, macro c.parse api and toolbox.
*/
def mkTreeOrBlock(stats: List[Tree]) = stats match {
case Nil => EmptyTree
case head :: Nil => head
case _ => mkBlock(stats)
}
/** Create a tree representing an assignment <lhs = rhs> */
def mkAssign(lhs: Tree, rhs: Tree): Tree = lhs match {
case Apply(fn, args) => Apply(atPos(fn.pos)(Select(fn, nme.update)), args :+ rhs)
case _ => Assign(lhs, rhs)
}
def mkPackageObject(defn: ModuleDef, pidPos: Position = NoPosition, pkgPos: Position = NoPosition) = {
val module = copyModuleDef(defn)(name = nme.PACKAGEkw)
val pid = atPos(pidPos)(Ident(defn.name))
atPos(pkgPos)(PackageDef(pid, module :: Nil))
}
// Following objects represent encoding of for loop enumerators
// into the regular trees. Such representations are used for:
//
// - as intermediate value of enumerators inside of the parser
// right before the mkFor desugaring is being called
//
// - as intermediate value of enumerators obtained after
// re-sugaring of for loops through build.SyntacticFor
// and build.SyntacticForYield (which are used by quasiquotes)
//
// The encoding uses regular trees with ForAttachment that helps
// to reliably differentiate them from normal trees that can have
// similar shape. fq"$pat <- $rhs" for example is represented in
// the same way as "`<-`($pat, $rhs)"" but with added attachment to
// the `<-` identifier.
//
// The primary rationale behind such representation in favor of
// simple case classes is a wish to re-use the same representation
// between quasiquotes and parser without exposing compiler internals.
// Opaque tree encoding can be changed/adapted at any time without
// breaking end users code.
/** Encode/decode fq"$pat <- $rhs" enumerator as q"`<-`($pat, $rhs)" */
object ValFrom {
def apply(pat: Tree, rhs: Tree): Tree =
Apply(Ident(nme.LARROWkw).updateAttachment(ForAttachment),
List(pat, rhs))
def unapply(tree: Tree): Option[(Tree, Tree)] = tree match {
case Apply(id @ Ident(nme.LARROWkw), List(pat, rhs))
if id.hasAttachment[ForAttachment.type] =>
Some((pat, rhs))
case _ => None
}
}
/** Encode/decode fq"$pat = $rhs" enumerator as q"$pat = $rhs" */
object ValEq {
def apply(pat: Tree, rhs: Tree): Tree =
Assign(pat, rhs).updateAttachment(ForAttachment)
def unapply(tree: Tree): Option[(Tree, Tree)] = tree match {
case Assign(pat, rhs)
if tree.hasAttachment[ForAttachment.type] =>
Some((pat, rhs))
case _ => None
}
}
/** Encode/decode fq"if $cond" enumerator as q"`if`($cond)" */
object Filter {
def apply(tree: Tree) =
Apply(Ident(nme.IFkw).updateAttachment(ForAttachment), List(tree))
def unapply(tree: Tree): Option[Tree] = tree match {
case Apply(id @ Ident(nme.IFkw), List(cond))
if id.hasAttachment[ForAttachment.type] =>
Some((cond))
case _ => None
}
}
/** Encode/decode body of for yield loop as q"`yield`($tree)" */
object Yield {
def apply(tree: Tree): Tree =
Apply(Ident(nme.YIELDkw).updateAttachment(ForAttachment), List(tree))
def unapply(tree: Tree): Option[Tree] = tree match {
case Apply(id @ Ident(nme.YIELDkw), List(tree))
if id.hasAttachment[ForAttachment.type] =>
Some(tree)
case _ => None
}
}
/** Create tree for for-comprehension <for (enums) do body> or
* <for (enums) yield body> where mapName and flatMapName are chosen
* corresponding to whether this is a for-do or a for-yield.
* The creation performs the following rewrite rules:
*
* 1.
*
* for (P <- G) E ==> G.foreach (P => E)
*
* Here and in the following (P => E) is interpreted as the function (P => E)
* if P is a variable pattern and as the partial function { case P => E } otherwise.
*
* 2.
*
* for (P <- G) yield E ==> G.map (P => E)
*
* 3.
*
* for (P_1 <- G_1; P_2 <- G_2; ...) ...
* ==>
* G_1.flatMap (P_1 => for (P_2 <- G_2; ...) ...)
*
* 4.
*
* for (P <- G; E; ...) ...
* =>
* for (P <- G.filter (P => E); ...) ...
*
* 5. For N < MaxTupleArity:
*
* for (P_1 <- G; P_2 = E_2; val P_N = E_N; ...)
* ==>
* for (TupleN(P_1, P_2, ... P_N) <-
* for (x_1 @ P_1 <- G) yield {
* val x_2 @ P_2 = E_2
* ...
* val x_N & P_N = E_N
* TupleN(x_1, ..., x_N)
* } ...)
*
* If any of the P_i are variable patterns, the corresponding `x_i @ P_i' is not generated
* and the variable constituting P_i is used instead of x_i
*
* @param mapName The name to be used for maps (either map or foreach)
* @param flatMapName The name to be used for flatMaps (either flatMap or foreach)
* @param enums The enumerators in the for expression
* @param body The body of the for expression
*/
def mkFor(enums: List[Tree], sugarBody: Tree)(implicit fresh: FreshNameCreator): Tree = {
val (mapName, flatMapName, body) = sugarBody match {
case Yield(tree) => (nme.map, nme.flatMap, tree)
case _ => (nme.foreach, nme.foreach, sugarBody)
}
/* make a closure pat => body.
* The closure is assigned a transparent position with the point at pos.point and
* the limits given by pat and body.
*/
def makeClosure(pos: Position, pat: Tree, body: Tree): Tree = {
def wrapped = wrappingPos(List(pat, body))
def splitpos = (if (pos != NoPosition) wrapped.withPoint(pos.point) else pos).makeTransparent
matchVarPattern(pat) match {
case Some((name, tpt)) =>
Function(
List(atPos(pat.pos) { ValDef(Modifiers(PARAM), name.toTermName, tpt, EmptyTree) }),
body) setPos splitpos
case None =>
atPos(splitpos) {
mkVisitor(List(CaseDef(pat, EmptyTree, body)), checkExhaustive = false)
}
}
}
/* Make an application qual.meth(pat => body) positioned at `pos`.
*/
def makeCombination(pos: Position, meth: TermName, qual: Tree, pat: Tree, body: Tree): Tree =
// ForAttachment on the method selection is used to differentiate
// result of for desugaring from a regular method call
Apply(Select(qual, meth) setPos qual.pos updateAttachment ForAttachment,
List(makeClosure(pos, pat, body))) setPos pos
/* If `pat` is not yet a `Bind` wrap it in one with a fresh name */
def makeBind(pat: Tree): Tree = pat match {
case Bind(_, _) => pat
case _ => Bind(freshTermName(), pat) setPos pat.pos
}
/* A reference to the name bound in Bind `pat`. */
def makeValue(pat: Tree): Tree = pat match {
case Bind(name, _) => Ident(name) setPos pat.pos.focus
}
/* The position of the closure that starts with generator at position `genpos`. */
def closurePos(genpos: Position) =
if (genpos == NoPosition) NoPosition
else {
val end = body.pos match {
case NoPosition => genpos.point
case bodypos => bodypos.end
}
rangePos(genpos.source, genpos.start, genpos.point, end)
}
enums match {
case (t @ ValFrom(pat, rhs)) :: Nil =>
makeCombination(closurePos(t.pos), mapName, rhs, pat, body)
case (t @ ValFrom(pat, rhs)) :: (rest @ (ValFrom(_, _) :: _)) =>
makeCombination(closurePos(t.pos), flatMapName, rhs, pat,
mkFor(rest, sugarBody))
case (t @ ValFrom(pat, rhs)) :: Filter(test) :: rest =>
mkFor(ValFrom(pat, makeCombination(rhs.pos union test.pos, nme.withFilter, rhs, pat.duplicate, test)).setPos(t.pos) :: rest, sugarBody)
case (t @ ValFrom(pat, rhs)) :: rest =>
val valeqs = rest.take(definitions.MaxTupleArity - 1).takeWhile { ValEq.unapply(_).nonEmpty }
assert(!valeqs.isEmpty)
val rest1 = rest.drop(valeqs.length)
val pats = valeqs map { case ValEq(pat, _) => pat }
val rhss = valeqs map { case ValEq(_, rhs) => rhs }
val defpat1 = makeBind(pat)
val defpats = pats map makeBind
val pdefs = (defpats, rhss).zipped flatMap mkPatDef
val ids = (defpat1 :: defpats) map makeValue
val rhs1 = mkFor(
List(ValFrom(defpat1, rhs).setPos(t.pos)),
Yield(Block(pdefs, atPos(wrappingPos(ids)) { mkTuple(ids) }) setPos wrappingPos(pdefs)))
val allpats = (pat :: pats) map (_.duplicate)
val pos1 =
if (t.pos == NoPosition) NoPosition
else rangePos(t.pos.source, t.pos.start, t.pos.point, rhs1.pos.end)
val vfrom1 = ValFrom(atPos(wrappingPos(allpats)) { mkTuple(allpats) }, rhs1).setPos(pos1)
mkFor(vfrom1 :: rest1, sugarBody)
case _ =>
EmptyTree //may happen for erroneous input
}
}
/** Create tree for pattern definition <val pat0 = rhs> */
def mkPatDef(pat: Tree, rhs: Tree)(implicit fresh: FreshNameCreator): List[ValDef] =
mkPatDef(Modifiers(0), pat, rhs)
/** Create tree for pattern definition <mods val pat0 = rhs> */
def mkPatDef(mods: Modifiers, pat: Tree, rhs: Tree)(implicit fresh: FreshNameCreator): List[ValDef] = matchVarPattern(pat) match {
case Some((name, tpt)) =>
List(atPos(pat.pos union rhs.pos) {
ValDef(mods, name.toTermName, tpt, rhs)
})
case None =>
// in case there is exactly one variable x_1 in pattern
// val/var p = e ==> val/var x_1 = e.match (case p => (x_1))
//
// in case there are zero or more than one variables in pattern
// val/var p = e ==> private synthetic val t$ = e.match (case p => (x_1, ..., x_N))
// val/var x_1 = t$._1
// ...
// val/var x_N = t$._N
val rhsUnchecked = mkUnchecked(rhs)
// TODO: clean this up -- there is too much information packked into mkPatDef's `pat` argument
// when it's a simple identifier (case Some((name, tpt)) -- above),
// pat should have the type ascription that was specified by the user
// however, in `case None` (here), we must be careful not to generate illegal pattern trees (such as `(a, b): Tuple2[Int, String]`)
// i.e., this must hold: pat1 match { case Typed(expr, tp) => assert(expr.isInstanceOf[Ident]) case _ => }
// if we encounter such an erroneous pattern, we strip off the type ascription from pat and propagate the type information to rhs
val (pat1, rhs1) = patvarTransformer.transform(pat) match {
// move the Typed ascription to the rhs
case Typed(expr, tpt) if !expr.isInstanceOf[Ident] =>
val rhsTypedUnchecked =
if (tpt.isEmpty) rhsUnchecked
else Typed(rhsUnchecked, tpt) setPos (rhs.pos union tpt.pos)
(expr, rhsTypedUnchecked)
case ok =>
(ok, rhsUnchecked)
}
val vars = getVariables(pat1)
val matchExpr = atPos((pat1.pos union rhs.pos).makeTransparent) {
Match(
rhs1,
List(
atPos(pat1.pos) {
CaseDef(pat1, EmptyTree, mkTuple(vars map (_._1) map Ident.apply))
}
))
}
vars match {
case List((vname, tpt, pos)) =>
List(atPos(pat.pos union pos union rhs.pos) {
ValDef(mods, vname.toTermName, tpt, matchExpr)
})
case _ =>
val tmp = freshTermName()
val firstDef =
atPos(matchExpr.pos) {
ValDef(Modifiers(PrivateLocal | SYNTHETIC | ARTIFACT | (mods.flags & LAZY)),
tmp, TypeTree(), matchExpr)
}
var cnt = 0
val restDefs = for ((vname, tpt, pos) <- vars) yield atPos(pos) {
cnt += 1
ValDef(mods, vname.toTermName, tpt, Select(Ident(tmp), newTermName("_" + cnt)))
}
firstDef :: restDefs
}
}
/** Create tree for for-comprehension generator <val pat0 <- rhs0> */
def mkGenerator(pos: Position, pat: Tree, valeq: Boolean, rhs: Tree)(implicit fresh: FreshNameCreator): Tree = {
val pat1 = patvarTransformer.transform(pat)
if (valeq) ValEq(pat1, rhs).setPos(pos)
else ValFrom(pat1, mkCheckIfRefutable(pat1, rhs)).setPos(pos)
}
def mkCheckIfRefutable(pat: Tree, rhs: Tree)(implicit fresh: FreshNameCreator) =
if (treeInfo.isVarPatternDeep(pat)) rhs
else {
val cases = List(
CaseDef(pat.duplicate, EmptyTree, Literal(Constant(true))),
CaseDef(Ident(nme.WILDCARD), EmptyTree, Literal(Constant(false)))
)
val visitor = mkVisitor(cases, checkExhaustive = false, nme.CHECK_IF_REFUTABLE_STRING)
atPos(rhs.pos)(Apply(Select(rhs, nme.withFilter), visitor :: Nil))
}
/** If tree is a variable pattern, return Some("its name and type").
* Otherwise return none */
private def matchVarPattern(tree: Tree): Option[(Name, Tree)] = {
def wildType(t: Tree): Option[Tree] = t match {
case Ident(x) if x.toTermName == nme.WILDCARD => Some(TypeTree())
case Typed(Ident(x), tpt) if x.toTermName == nme.WILDCARD => Some(tpt)
case _ => None
}
tree match {
case Ident(name) => Some((name, TypeTree()))
case Bind(name, body) => wildType(body) map (x => (name, x))
case Typed(Ident(name), tpt) => Some((name, tpt))
case _ => None
}
}
/** Create visitor <x => x match cases> */
def mkVisitor(cases: List[CaseDef], checkExhaustive: Boolean, prefix: String = "x$")(implicit fresh: FreshNameCreator): Tree = {
val x = freshTermName(prefix)
val id = Ident(x)
val sel = if (checkExhaustive) id else mkUnchecked(id)
Function(List(mkSyntheticParam(x)), Match(sel, cases))
}
/** Traverse pattern and collect all variable names with their types in buffer
* The variables keep their positions; whereas the pattern is converted to be
* synthetic for all nodes that contain a variable position.
*/
class GetVarTraverser extends Traverser {
val buf = new ListBuffer[(Name, Tree, Position)]
def namePos(tree: Tree, name: Name): Position =
if (!tree.pos.isRange || name.containsName(nme.raw.DOLLAR)) tree.pos.focus
else {
val start = tree.pos.start
val end = start + name.decode.length
rangePos(tree.pos.source, start, start, end)
}
override def traverse(tree: Tree): Unit = {
def seenName(name: Name) = buf exists (_._1 == name)
def add(name: Name, t: Tree) = if (!seenName(name)) buf += ((name, t, namePos(tree, name)))
val bl = buf.length
tree match {
case Bind(nme.WILDCARD, _) =>
super.traverse(tree)
case Bind(name, Typed(tree1, tpt)) =>
val newTree = if (treeInfo.mayBeTypePat(tpt)) TypeTree() else tpt.duplicate
add(name, newTree)
traverse(tree1)
case Bind(name, tree1) =>
// can assume only name range as position, as otherwise might overlap
// with binds embedded in pattern tree1
add(name, TypeTree())
traverse(tree1)
case _ =>
super.traverse(tree)
}
if (buf.length > bl)
tree setPos tree.pos.makeTransparent
}
def apply(tree: Tree) = {
traverse(tree)
buf.toList
}
}
/** Returns list of all pattern variables, possibly with their types,
* without duplicates
*/
private def getVariables(tree: Tree): List[(Name, Tree, Position)] =
new GetVarTraverser apply tree
/** Convert all occurrences of (lower-case) variables in a pattern as follows:
* x becomes x @ _
* x: T becomes x @ (_: T)
*/
object patvarTransformer extends Transformer {
override def transform(tree: Tree): Tree = tree match {
case Ident(name) if (treeInfo.isVarPattern(tree) && name != nme.WILDCARD) =>
atPos(tree.pos)(Bind(name, atPos(tree.pos.focus) (Ident(nme.WILDCARD))))
case Typed(id @ Ident(name), tpt) if (treeInfo.isVarPattern(id) && name != nme.WILDCARD) =>
atPos(tree.pos.withPoint(id.pos.point)) {
Bind(name, atPos(tree.pos.withStart(tree.pos.point)) {
Typed(Ident(nme.WILDCARD), tpt)
})
}
case Apply(fn @ Apply(_, _), args) =>
treeCopy.Apply(tree, transform(fn), transformTrees(args))
case Apply(fn, args) =>
treeCopy.Apply(tree, fn, transformTrees(args))
case Typed(expr, tpt) =>
treeCopy.Typed(tree, transform(expr), tpt)
case Bind(name, body) =>
treeCopy.Bind(tree, name, transform(body))
case Alternative(_) | Star(_) =>
super.transform(tree)
case _ =>
tree
}
}
// annotate the expression with @unchecked
def mkUnchecked(expr: Tree): Tree = atPos(expr.pos) {
// This can't be "Annotated(New(UncheckedClass), expr)" because annotations
// are very picky about things and it crashes the compiler with "unexpected new".
Annotated(New(scalaDot(tpnme.unchecked), Nil), expr)
}
def mkSyntheticParam(pname: TermName) =
ValDef(Modifiers(PARAM | SYNTHETIC), pname, TypeTree(), EmptyTree)
def mkCast(tree: Tree, pt: Type): Tree =
atPos(tree.pos)(mkAsInstanceOf(tree, pt, any = true, wrapInApply = false))
}
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