Scala example source code file (UnCurry.scala)
The UnCurry.scala Scala example source code
/* NSC -- new Scala compiler
* Copyright 2005-2013 LAMP/EPFL
* @author
*/
package scala
package tools.nsc
package transform
import symtab.Flags._
import scala.collection.{ mutable, immutable }
import scala.language.postfixOps
/*<export> */
/** - uncurry all symbol and tree types (@see UnCurryPhase) -- this includes normalizing all proper types.
* - for every curried parameter list: (ps_1) ... (ps_n) ==> (ps_1, ..., ps_n)
* - for every curried application: f(args_1)...(args_n) ==> f(args_1, ..., args_n)
* - for every type application: f[Ts] ==> f[Ts]() unless followed by parameters
* - for every use of a parameterless function: f ==> f() and q.f ==> q.f()
* - for every def-parameter: x: => T ==> x: () => T
* - for every use of a def-parameter: x ==> x.apply()
* - for every argument to a def parameter `x: => T':
* if argument is not a reference to a def parameter:
* convert argument `e` to (expansion of) `() => e'
* - for every repeated Scala parameter `x: T*' --> x: Seq[T].
* - for every repeated Java parameter `x: T...' --> x: Array[T], except:
* if T is an unbounded abstract type, replace --> x: Array[Object]
* - for every argument list that corresponds to a repeated Scala parameter
* (a_1, ..., a_n) => (Seq(a_1, ..., a_n))
* - for every argument list that corresponds to a repeated Java parameter
* (a_1, ..., a_n) => (Array(a_1, ..., a_n))
* - for every argument list that is an escaped sequence
* (a_1:_*) => (a_1) (possibly converted to sequence or array, as needed)
* - convert implicit method types to method types
* - convert non-trivial catches in try statements to matches
* - convert non-local returns to throws with enclosing try statements.
* - convert try-catch expressions in contexts where there might be values on the stack to
* a local method and a call to it (since an exception empties the evaluation stack):
*
* meth(x_1,..., try { x_i } catch { ..}, .. x_b0) ==>
* {
* def liftedTry$1 = try { x_i } catch { .. }
* meth(x_1, .., liftedTry$1(), .. )
* }
*/
/*</export> */
abstract class UnCurry extends InfoTransform
with scala.reflect.internal.transform.UnCurry
with TypingTransformers with ast.TreeDSL {
val global: Global // need to repeat here because otherwise last mixin defines global as
// SymbolTable. If we had DOT this would not be an issue
import global._ // the global environment
import definitions._ // standard classes and methods
import CODE._
val phaseName: String = "uncurry"
def newTransformer(unit: CompilationUnit): Transformer = new UnCurryTransformer(unit)
override def changesBaseClasses = false
// ------ Type transformation --------------------------------------------------------
// uncurry and uncurryType expand type aliases
class UnCurryTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {
private val inlineFunctionExpansion = settings.Ydelambdafy.value == "inline"
private var needTryLift = false
private var inConstructorFlag = 0L
private val byNameArgs = mutable.HashSet[Tree]()
private val noApply = mutable.HashSet[Tree]()
private val newMembers = mutable.Map[Symbol, mutable.Buffer[Tree]]()
private val repeatedParams = mutable.Map[Symbol, List[ValDef]]()
/** Add a new synthetic member for `currentOwner` */
private def addNewMember(t: Tree): Unit =
newMembers.getOrElseUpdate(currentOwner, mutable.Buffer()) += t
/** Process synthetic members for `owner`. They are removed form the `newMembers` as a side-effect. */
@inline private def useNewMembers[T](owner: Symbol)(f: List[Tree] => T): T =
f(newMembers.remove(owner).getOrElse(Nil).toList)
private def newFunction0(body: Tree): Tree = {
val result = localTyper.typedPos(body.pos)(Function(Nil, body)).asInstanceOf[Function]
log("Change owner from %s to %s in %s".format(currentOwner, result.symbol, result.body))
result.body changeOwner (currentOwner -> result.symbol)
transformFunction(result)
}
// I don't have a clue why I'm catching TypeErrors here, but it's better
// than spewing stack traces at end users for internal errors. Examples
// which hit at this point should not be hard to come by, but the immediate
// motivation can be seen in continuations-neg/t3718.
override def transform(tree: Tree): Tree = (
try postTransform(mainTransform(tree))
catch { case ex: TypeError =>
unit.error(ex.pos, ex.msg)
debugStack(ex)
EmptyTree
}
)
/* Is tree a reference `x` to a call by name parameter that needs to be converted to
* x.apply()? Note that this is not the case if `x` is used as an argument to another
* call by name parameter.
*/
def isByNameRef(tree: Tree) = (
tree.isTerm
&& (tree.symbol ne null)
&& (isByName(tree.symbol))
&& !byNameArgs(tree)
)
// ------- Handling non-local returns -------------------------------------------------
/** The type of a non-local return expression with given argument type */
private def nonLocalReturnExceptionType(argtype: Type) =
appliedType(NonLocalReturnControlClass, argtype)
/** A hashmap from method symbols to non-local return keys */
private val nonLocalReturnKeys = perRunCaches.newMap[Symbol, Symbol]()
/** Return non-local return key for given method */
private def nonLocalReturnKey(meth: Symbol) =
nonLocalReturnKeys.getOrElseUpdate(meth,
meth.newValue(unit.freshTermName("nonLocalReturnKey"), meth.pos, SYNTHETIC) setInfo ObjectTpe
)
/** Generate a non-local return throw with given return expression from given method.
* I.e. for the method's non-local return key, generate:
*
* throw new NonLocalReturnControl(key, expr)
* todo: maybe clone a pre-existing exception instead?
* (but what to do about exceptions that miss their targets?)
*/
private def nonLocalReturnThrow(expr: Tree, meth: Symbol) = localTyper typed {
Throw(
nonLocalReturnExceptionType(expr.tpe.widen),
Ident(nonLocalReturnKey(meth)),
expr
)
}
/** Transform (body, key) to:
*
* {
* val key = new Object()
* try {
* body
* } catch {
* case ex: NonLocalReturnControl[T @unchecked] =>
* if (ex.key().eq(key)) ex.value()
* else throw ex
* }
* }
*/
private def nonLocalReturnTry(body: Tree, key: Symbol, meth: Symbol) = {
localTyper typed {
val restpe = meth.tpe_*.finalResultType
val extpe = nonLocalReturnExceptionType(restpe)
val ex = meth.newValue(nme.ex, body.pos) setInfo extpe
val argType = restpe withAnnotation (AnnotationInfo marker UncheckedClass.tpe)
val pat = gen.mkBindForCase(ex, NonLocalReturnControlClass, List(argType))
val rhs = (
IF ((ex DOT nme.key)() OBJ_EQ Ident(key))
THEN ((ex DOT nme.value)())
ELSE (Throw(Ident(ex)))
)
val keyDef = ValDef(key, New(ObjectTpe))
val tryCatch = Try(body, pat -> rhs)
import treeInfo.{catchesThrowable, isSyntheticCase}
for {
Try(t, catches, _) <- body
cdef <- catches
if catchesThrowable(cdef) && !isSyntheticCase(cdef)
} {
unit.warning(body.pos, "catch block may intercept non-local return from " + meth)
}
Block(List(keyDef), tryCatch)
}
}
// ------ Transforming anonymous functions and by-name-arguments ----------------
/** Undo eta expansion for parameterless and nullary methods */
def deEta(fun: Function): Tree = fun match {
case Function(List(), expr) if isByNameRef(expr) =>
noApply += expr
expr
case _ =>
fun
}
/** Transform a function node (x_1,...,x_n) => body of type FunctionN[T_1, .., T_N, R] to
*
* class $anon() extends AbstractFunctionN[T_1, .., T_N, R] with Serializable {
* def apply(x_1: T_1, ..., x_N: T_n): R = body
* }
* new $anon()
*
*/
def transformFunction(fun: Function): Tree = {
fun.tpe match {
// can happen when analyzer plugins assign refined types to functions, e.g.
// (() => Int) { def apply(): Int @typeConstraint }
case RefinedType(List(funTp), decls) =>
debuglog(s"eliminate refinement from function type ${fun.tpe}")
fun.tpe = funTp
case _ =>
()
}
deEta(fun) match {
// nullary or parameterless
case fun1 if fun1 ne fun => fun1
case _ =>
def typedFunPos(t: Tree) = localTyper.typedPos(fun.pos)(t)
val funParams = fun.vparams map (_.symbol)
def mkMethod(owner: Symbol, name: TermName, additionalFlags: FlagSet = NoFlags): DefDef =
gen.mkMethodFromFunction(localTyper)(fun, owner, name, additionalFlags)
val canUseDelamdafyMethod = (inConstructorFlag == 0) // Avoiding synthesizing code prone to SI-6666, SI-8363 by using old-style lambda translation
if (inlineFunctionExpansion || !canUseDelamdafyMethod) {
val parents = addSerializable(abstractFunctionForFunctionType(fun.tpe))
val anonClass = fun.symbol.owner newAnonymousFunctionClass(fun.pos, inConstructorFlag) addAnnotation SerialVersionUIDAnnotation
anonClass setInfo ClassInfoType(parents, newScope, anonClass)
val applyMethodDef = mkMethod(anonClass, nme.apply)
anonClass.info.decls enter applyMethodDef.symbol
typedFunPos {
Block(
ClassDef(anonClass, NoMods, ListOfNil, List(applyMethodDef), fun.pos),
Typed(New(anonClass.tpe), TypeTree(fun.tpe)))
}
} else {
// method definition with the same arguments, return type, and body as the original lambda
val liftedMethod = mkMethod(fun.symbol.owner, nme.ANON_FUN_NAME, additionalFlags = ARTIFACT)
// new function whose body is just a call to the lifted method
val newFun = deriveFunction(fun)(_ => typedFunPos(
gen.mkForwarder(gen.mkAttributedRef(liftedMethod.symbol), funParams :: Nil)
))
typedFunPos(Block(liftedMethod, super.transform(newFun)))
}
}
}
def transformArgs(pos: Position, fun: Symbol, args: List[Tree], formals: List[Type]) = {
val isJava = fun.isJavaDefined
def transformVarargs(varargsElemType: Type) = {
def mkArrayValue(ts: List[Tree], elemtp: Type) =
ArrayValue(TypeTree(elemtp), ts) setType arrayType(elemtp)
// when calling into scala varargs, make sure it's a sequence.
def arrayToSequence(tree: Tree, elemtp: Type) = {
exitingUncurry {
localTyper.typedPos(pos) {
val pt = arrayType(elemtp)
val adaptedTree = // might need to cast to Array[elemtp], as arrays are not covariant
if (tree.tpe <:< pt) tree
else gen.mkCastArray(tree, elemtp, pt)
gen.mkWrapArray(adaptedTree, elemtp)
}
}
}
// when calling into java varargs, make sure it's an array - see bug #1360
def sequenceToArray(tree: Tree) = {
val toArraySym = tree.tpe member nme.toArray
assert(toArraySym != NoSymbol)
def getClassTag(tp: Type): Tree = {
val tag = localTyper.resolveClassTag(tree.pos, tp)
// Don't want bottom types getting any further than this (SI-4024)
if (tp.typeSymbol.isBottomClass) getClassTag(AnyTpe)
else if (!tag.isEmpty) tag
else if (tp.bounds.hi ne tp) getClassTag(tp.bounds.hi)
else localTyper.TyperErrorGen.MissingClassTagError(tree, tp)
}
def traversableClassTag(tpe: Type): Tree = {
(tpe baseType TraversableClass).typeArgs match {
case targ :: _ => getClassTag(targ)
case _ => EmptyTree
}
}
exitingUncurry {
localTyper.typedPos(pos) {
gen.mkMethodCall(tree, toArraySym, Nil, List(traversableClassTag(tree.tpe)))
}
}
}
var suffix: Tree =
if (treeInfo isWildcardStarArgList args) {
val Typed(tree, _) = args.last
if (isJava)
if (tree.tpe.typeSymbol == ArrayClass) tree
else sequenceToArray(tree)
else
if (tree.tpe.typeSymbol isSubClass SeqClass) tree
else arrayToSequence(tree, varargsElemType)
}
else {
def mkArray = mkArrayValue(args drop (formals.length - 1), varargsElemType)
if (isJava) mkArray
else if (args.isEmpty) gen.mkNil // avoid needlessly double-wrapping an empty argument list
else arrayToSequence(mkArray, varargsElemType)
}
exitingUncurry {
if (isJava && !isReferenceArray(suffix.tpe) && isArrayOfSymbol(fun.tpe.params.last.tpe, ObjectClass)) {
// The array isn't statically known to be a reference array, so call ScalaRuntime.toObjectArray.
suffix = localTyper.typedPos(pos) {
gen.mkRuntimeCall(nme.toObjectArray, List(suffix))
}
}
}
args.take(formals.length - 1) :+ (suffix setType formals.last)
}
val args1 = if (isVarArgTypes(formals)) transformVarargs(formals.last.typeArgs.head) else args
map2(formals, args1) { (formal, arg) =>
if (!isByNameParamType(formal))
arg
else if (isByNameRef(arg)) {
byNameArgs += arg
arg setType functionType(Nil, arg.tpe)
}
else {
log(s"Argument '$arg' at line ${arg.pos.line} is $formal from ${fun.fullName}")
def canUseDirectly(recv: Tree) = (
recv.tpe.typeSymbol.isSubClass(FunctionClass(0))
&& treeInfo.isExprSafeToInline(recv)
)
arg match {
// don't add a thunk for by-name argument if argument already is an application of
// a Function0. We can then remove the application and use the existing Function0.
case Apply(Select(recv, nme.apply), Nil) if canUseDirectly(recv) =>
recv
case _ =>
newFunction0(arg)
}
}
}
}
/** Called if a tree's symbol is elidable. If it's a DefDef,
* replace only the body/rhs with 0/false/()/null; otherwise replace
* the whole tree with it.
*/
private def replaceElidableTree(tree: Tree): Tree = {
tree match {
case DefDef(_,_,_,_,_,_) =>
deriveDefDef(tree)(rhs => Block(Nil, gen.mkZero(rhs.tpe)) setType rhs.tpe) setSymbol tree.symbol setType tree.tpe
case _ =>
gen.mkZero(tree.tpe) setType tree.tpe
}
}
private def isSelfSynchronized(ddef: DefDef) = ddef.rhs match {
case Apply(fn @ TypeApply(Select(sel, _), _), _) =>
fn.symbol == Object_synchronized && sel.symbol == ddef.symbol.enclClass && !ddef.symbol.enclClass.isTrait
case _ => false
}
/** If an eligible method is entirely wrapped in a call to synchronized
* locked on the same instance, remove the synchronized scaffolding and
* mark the method symbol SYNCHRONIZED for bytecode generation.
*/
private def translateSynchronized(tree: Tree) = tree match {
case dd @ DefDef(_, _, _, _, _, Apply(fn, body :: Nil)) if isSelfSynchronized(dd) =>
log("Translating " + dd.symbol.defString + " into synchronized method")
dd.symbol setFlag SYNCHRONIZED
deriveDefDef(dd)(_ => body)
case _ => tree
}
def isNonLocalReturn(ret: Return) = ret.symbol != currentOwner.enclMethod || currentOwner.isLazy || currentOwner.isAnonymousFunction
// ------ The tree transformers --------------------------------------------------------
def mainTransform(tree: Tree): Tree = {
@inline def withNeedLift(needLift: Boolean)(f: => Tree): Tree = {
val saved = needTryLift
needTryLift = needLift
try f
finally needTryLift = saved
}
/* Transform tree `t` to { def f = t; f } where `f` is a fresh name */
def liftTree(tree: Tree) = {
debuglog("lifting tree at: " + (tree.pos))
val sym = currentOwner.newMethod(unit.freshTermName("liftedTree"), tree.pos)
sym.setInfo(MethodType(List(), tree.tpe))
tree.changeOwner(currentOwner -> sym)
localTyper.typedPos(tree.pos)(Block(
List(DefDef(sym, ListOfNil, tree)),
Apply(Ident(sym), Nil)
))
}
def withInConstructorFlag(inConstructorFlag: Long)(f: => Tree): Tree = {
val saved = this.inConstructorFlag
this.inConstructorFlag = inConstructorFlag
try f
finally this.inConstructorFlag = saved
}
val sym = tree.symbol
// true if the taget is a lambda body that's been lifted into a method
def isLiftedLambdaBody(target: Tree) = target.symbol.isLocalToBlock && target.symbol.isArtifact && target.symbol.name.containsName(nme.ANON_FUN_NAME)
val result = (
// TODO - settings.noassertions.value temporarily retained to avoid
// breakage until a reasonable interface is settled upon.
if ((sym ne null) && (sym.elisionLevel.exists (_ < settings.elidebelow.value || settings.noassertions)))
replaceElidableTree(tree)
else translateSynchronized(tree) match {
case dd @ DefDef(mods, name, tparams, _, tpt, rhs) =>
// Remove default argument trees from parameter ValDefs, SI-4812
val vparamssNoRhs = dd.vparamss mapConserve (_ mapConserve {p =>
treeCopy.ValDef(p, p.mods, p.name, p.tpt, EmptyTree)
})
if (dd.symbol hasAnnotation VarargsClass) saveRepeatedParams(dd)
withNeedLift(needLift = false) {
if (dd.symbol.isClassConstructor) {
atOwner(sym) {
val rhs1 = (rhs: @unchecked) match {
case Block(stats, expr) =>
def transformInConstructor(stat: Tree) =
withInConstructorFlag(INCONSTRUCTOR) { transform(stat) }
val presupers = treeInfo.preSuperFields(stats) map transformInConstructor
val rest = stats drop presupers.length
val supercalls = rest take 1 map transformInConstructor
val others = rest drop 1 map transform
treeCopy.Block(rhs, presupers ::: supercalls ::: others, transform(expr))
}
treeCopy.DefDef(
dd, mods, name, transformTypeDefs(tparams),
transformValDefss(vparamssNoRhs), transform(tpt), rhs1)
}
} else {
super.transform(treeCopy.DefDef(dd, mods, name, tparams, vparamssNoRhs, tpt, rhs))
}
}
case ValDef(_, _, _, rhs) =>
if (sym eq NoSymbol) throw new IllegalStateException("Encountered Valdef without symbol: "+ tree + " in "+ unit)
if (!sym.owner.isSourceMethod)
withNeedLift(needLift = true) { super.transform(tree) }
else
super.transform(tree)
case UnApply(fn, args) =>
val fn1 = transform(fn)
val args1 = fn.symbol.name match {
case nme.unapplySeq => transformArgs(tree.pos, fn.symbol, args, patmat.alignPatterns(tree).expectedTypes)
case _ => args
}
treeCopy.UnApply(tree, fn1, args1)
case Apply(fn, args) =>
val needLift = needTryLift || !fn.symbol.isLabel // SI-6749, no need to lift in args to label jumps.
withNeedLift(needLift) {
val formals = fn.tpe.paramTypes
treeCopy.Apply(tree, transform(fn), transformTrees(transformArgs(tree.pos, fn.symbol, args, formals)))
}
case Assign(_: RefTree, _) =>
withNeedLift(needLift = true) { super.transform(tree) }
case Assign(lhs, _) if lhs.symbol.owner != currentMethod || lhs.symbol.hasFlag(LAZY | ACCESSOR) =>
withNeedLift(needLift = true) { super.transform(tree) }
case ret @ Return(_) if (isNonLocalReturn(ret)) =>
withNeedLift(needLift = true) { super.transform(ret) }
case Try(_, Nil, _) =>
// try-finally does not need lifting: lifting is needed only for try-catch
// expressions that are evaluated in a context where the stack might not be empty.
// `finally` does not attempt to continue evaluation after an exception, so the fact
// that values on the stack are 'lost' does not matter
super.transform(tree)
case Try(block, catches, finalizer) =>
if (needTryLift) transform(liftTree(tree))
else super.transform(tree)
case CaseDef(pat, guard, body) =>
val pat1 = transform(pat)
treeCopy.CaseDef(tree, pat1, transform(guard), transform(body))
// if a lambda is already the right shape we don't need to transform it again
case fun @ Function(_, Apply(target, _)) if (!inlineFunctionExpansion) && isLiftedLambdaBody(target) =>
super.transform(fun)
case fun @ Function(_, _) =>
mainTransform(transformFunction(fun))
case Template(_, _, _) =>
withInConstructorFlag(0) { super.transform(tree) }
case _ =>
val tree1 = super.transform(tree)
if (isByNameRef(tree1)) {
val tree2 = tree1 setType functionType(Nil, tree1.tpe)
return {
if (noApply contains tree2) tree2
else localTyper.typedPos(tree1.pos)(Apply(Select(tree2, nme.apply), Nil))
}
}
tree1
}
)
assert(result.tpe != null, result.shortClass + " tpe is null:\n" + result)
result modifyType uncurry
}
def postTransform(tree: Tree): Tree = exitingUncurry {
def applyUnary(): Tree = {
// TODO_NMT: verify that the inner tree of a type-apply also gets parens if the
// whole tree is a polymorphic nullary method application
def removeNullary() = tree.tpe match {
case MethodType(_, _) => tree
case tp => tree setType MethodType(Nil, tp.resultType)
}
if (tree.symbol.isMethod && !tree.tpe.isInstanceOf[PolyType])
gen.mkApplyIfNeeded(removeNullary())
else if (tree.isType)
TypeTree(tree.tpe) setPos tree.pos
else
tree
}
def isThrowable(pat: Tree): Boolean = pat match {
case Typed(Ident(nme.WILDCARD), tpt) =>
tpt.tpe =:= ThrowableTpe
case Bind(_, pat) =>
isThrowable(pat)
case _ =>
false
}
tree match {
/* Some uncurry post transformations add members to templates.
*
* Members registered by `addMembers` for the current template are added
* once the template transformation has finished.
*
* In particular, this case will add:
* - synthetic Java varargs forwarders for repeated parameters
*/
case Template(_, _, _) =>
localTyper = typer.atOwner(tree, currentClass)
useNewMembers(currentClass) {
newMembers =>
deriveTemplate(tree)(transformTrees(newMembers) ::: _)
}
case dd @ DefDef(_, _, _, vparamss0, _, rhs0) =>
val (newParamss, newRhs): (List[List[ValDef]], Tree) =
if (dependentParamTypeErasure isDependent dd)
dependentParamTypeErasure erase dd
else {
val vparamss1 = vparamss0 match {
case _ :: Nil => vparamss0
case _ => vparamss0.flatten :: Nil
}
(vparamss1, rhs0)
}
val flatdd = copyDefDef(dd)(
vparamss = newParamss,
rhs = nonLocalReturnKeys get dd.symbol match {
case Some(k) => atPos(newRhs.pos)(nonLocalReturnTry(newRhs, k, dd.symbol))
case None => newRhs
}
)
addJavaVarargsForwarders(dd, flatdd)
case tree: Try =>
if (tree.catches exists (cd => !treeInfo.isCatchCase(cd)))
devWarning("VPM BUG - illegal try/catch " + tree.catches)
tree
case Apply(Apply(fn, args), args1) =>
treeCopy.Apply(tree, fn, args ::: args1)
case Ident(name) =>
assert(name != tpnme.WILDCARD_STAR, tree)
applyUnary()
case Select(_, _) | TypeApply(_, _) =>
applyUnary()
case ret @ Return(expr) if isNonLocalReturn(ret) =>
log("non-local return from %s to %s".format(currentOwner.enclMethod, ret.symbol))
atPos(ret.pos)(nonLocalReturnThrow(expr, ret.symbol))
case TypeTree() =>
tree
case _ =>
if (tree.isType) TypeTree(tree.tpe) setPos tree.pos else tree
}
}
/**
* When we concatenate parameter lists, formal parameter types that were dependent
* on prior parameter values will no longer be correctly scoped.
*
* For example:
*
* {{{
* def foo(a: A)(b: a.B): a.type = {b; b}
* // after uncurry
* def foo(a: A, b: a/* NOT IN SCOPE! */.B): a.B = {b; b}
* }}}
*
* This violates the principle that each compiler phase should produce trees that
* can be retyped (see [[scala.tools.nsc.typechecker.TreeCheckers]]), and causes
* a practical problem in `erasure`: it is not able to correctly determine if
* such a signature overrides a corresponding signature in a parent. (SI-6443).
*
* This transformation erases the dependent method types by:
* - Widening the formal parameter type to existentially abstract
* over the prior parameters (using `packSymbols`). This transformation
* is performed in the the `InfoTransform`er [[scala.reflect.internal.transform.UnCurry]].
* - Inserting casts in the method body to cast to the original,
* precise type.
*
* For the example above, this results in:
*
* {{{
* def foo(a: A, b: a.B forSome { val a: A }): a.B = { val b$1 = b.asInstanceOf[a.B]; b$1; b$1 }
* }}}
*/
private object dependentParamTypeErasure {
sealed abstract class ParamTransform {
def param: ValDef
}
final case class Identity(param: ValDef) extends ParamTransform
final case class Packed(param: ValDef, tempVal: ValDef) extends ParamTransform
def isDependent(dd: DefDef): Boolean =
enteringUncurry {
val methType = dd.symbol.info
methType.isDependentMethodType && mexists(methType.paramss)(_.info exists (_.isImmediatelyDependent))
}
/**
* @return (newVparamss, newRhs)
*/
def erase(dd: DefDef): (List[List[ValDef]], Tree) = {
import dd.{ vparamss, rhs }
val paramTransforms: List[ParamTransform] =
map2(vparamss.flatten, dd.symbol.info.paramss.flatten) { (p, infoParam) =>
val packedType = infoParam.info
if (packedType =:= p.symbol.info) Identity(p)
else {
// The Uncurry info transformer existentially abstracted over value parameters
// from the previous parameter lists.
// Change the type of the param symbol
p.symbol updateInfo packedType
// Create a new param tree
val newParam: ValDef = copyValDef(p)(tpt = TypeTree(packedType))
// Within the method body, we'll cast the parameter to the originally
// declared type and assign this to a synthetic val. Later, we'll patch
// the method body to refer to this, rather than the parameter.
val tempVal: ValDef = {
val tempValName = unit freshTermName (p.name + "$")
val newSym = dd.symbol.newTermSymbol(tempValName, p.pos, SYNTHETIC).setInfo(p.symbol.info)
atPos(p.pos)(ValDef(newSym, gen.mkAttributedCast(Ident(p.symbol), p.symbol.info)))
}
Packed(newParam, tempVal)
}
}
val allParams = paramTransforms map (_.param)
val (packedParams, tempVals) = paramTransforms.collect {
case Packed(param, tempVal) => (param, tempVal)
}.unzip
val rhs1 = if (tempVals.isEmpty) rhs else {
localTyper.typedPos(rhs.pos) {
// Patch the method body to refer to the temp vals
val rhsSubstituted = rhs.substituteSymbols(packedParams map (_.symbol), tempVals map (_.symbol))
// The new method body: { val p$1 = p.asInstanceOf[<dependent type>]; ...; <rhsSubstituted> }
Block(tempVals, rhsSubstituted)
}
}
(allParams :: Nil, rhs1)
}
}
/* Analyzes repeated params if method is annotated as `varargs`.
* If the repeated params exist, it saves them into the `repeatedParams` map,
* which is used later.
*/
private def saveRepeatedParams(dd: DefDef): Unit =
if (dd.symbol.isConstructor)
unit.error(dd.symbol.pos, "A constructor cannot be annotated with a `varargs` annotation.")
else treeInfo.repeatedParams(dd) match {
case Nil =>
unit.error(dd.symbol.pos, "A method without repeated parameters cannot be annotated with the `varargs` annotation.")
case reps =>
repeatedParams(dd.symbol) = reps
}
/* Called during post transform, after the method argument lists have been flattened.
* It looks for the method in the `repeatedParams` map, and generates a Java-style
* varargs forwarder.
*/
private def addJavaVarargsForwarders(dd: DefDef, flatdd: DefDef): DefDef = {
if (!dd.symbol.hasAnnotation(VarargsClass) || !repeatedParams.contains(dd.symbol))
return flatdd
def toArrayType(tp: Type): Type = {
val arg = elementType(SeqClass, tp)
// to prevent generation of an `Object` parameter from `Array[T]` parameter later
// as this would crash the Java compiler which expects an `Object[]` array for varargs
// e.g. def foo[T](a: Int, b: T*)
// becomes def foo[T](a: Int, b: Array[Object])
// instead of def foo[T](a: Int, b: Array[T]) ===> def foo[T](a: Int, b: Object)
arrayType(
if (arg.typeSymbol.isTypeParameterOrSkolem) ObjectTpe
else arg
)
}
val reps = repeatedParams(dd.symbol)
val rpsymbols = reps.map(_.symbol).toSet
val theTyper = typer.atOwner(dd, currentClass)
val flatparams = flatdd.vparamss.head
// create the type
val forwformals = flatparams map {
case p if rpsymbols(p.symbol) => toArrayType(p.symbol.tpe)
case p => p.symbol.tpe
}
val forwresult = dd.symbol.tpe_*.finalResultType
val forwformsyms = map2(forwformals, flatparams)((tp, oldparam) =>
currentClass.newValueParameter(oldparam.name, oldparam.symbol.pos).setInfo(tp)
)
def mono = MethodType(forwformsyms, forwresult)
val forwtype = dd.symbol.tpe match {
case MethodType(_, _) => mono
case PolyType(tps, _) => PolyType(tps, mono)
}
// create the symbol
val forwsym = currentClass.newMethod(dd.name.toTermName, dd.pos, VARARGS | SYNTHETIC | flatdd.symbol.flags) setInfo forwtype
def forwParams = forwsym.info.paramss.flatten
// create the tree
val forwtree = theTyper.typedPos(dd.pos) {
val locals = map2(forwParams, flatparams) {
case (_, fp) if !rpsymbols(fp.symbol) => null
case (argsym, fp) =>
Block(Nil,
gen.mkCast(
gen.mkWrapArray(Ident(argsym), elementType(ArrayClass, argsym.tpe)),
seqType(elementType(SeqClass, fp.symbol.tpe))
)
)
}
val seqargs = map2(locals, forwParams) {
case (null, argsym) => Ident(argsym)
case (l, _) => l
}
val end = if (forwsym.isConstructor) List(UNIT) else Nil
DefDef(forwsym, BLOCK(Apply(gen.mkAttributedRef(flatdd.symbol), seqargs) :: end : _*))
}
// check if the method with that name and those arguments already exists in the template
currentClass.info.member(forwsym.name).alternatives.find(s => s != forwsym && s.tpe.matches(forwsym.tpe)) match {
case Some(s) => unit.error(dd.symbol.pos,
"A method with a varargs annotation produces a forwarder method with the same signature "
+ s.tpe + " as an existing method.")
case None =>
// enter symbol into scope
currentClass.info.decls enter forwsym
addNewMember(forwtree)
}
flatdd
}
}
}
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