scala.tools.nsc.transform.UnCurry.scala Maven / Gradle / Ivy
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/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc. dba Akka
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala
package tools.nsc
package transform
import scala.PartialFunction.cond
import scala.annotation.tailrec
import scala.collection.mutable
import scala.collection.mutable.ListBuffer
import scala.reflect.internal.util.ListOfNil
import scala.tools.nsc.Reporting.WarningCategory
import scala.tools.nsc.symtab.Flags._
/** - 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 method defining repeated parameters annotated with @varargs, generate
* a synthetic Java-style vararg method
* - 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(), .. )
* }
* - remove calls to elidable methods and replace their bodies with NOPs when elide-below
* requires it
*/
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 CODE._
import global._
import definitions._
val phaseName: String = "uncurry"
def newTransformer(unit: CompilationUnit): AstTransformer = new UnCurryTransformer(unit)
override def changesBaseClasses = false
// ------ Type transformation --------------------------------------------------------
// uncurry and uncurryType expand type aliases
class UnCurryTransformer(unit: CompilationUnit) extends TypingTransformer(unit) {
private val forceExpandFunction = 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]]()
// Expand `Function`s in constructors to class instance creation (scala/bug#6666, scala/bug#8363)
// We use Java's LambdaMetaFactory (LMF), which requires an interface for the sam's owner
private def mustExpandFunction(fun: Function) = {
// (TODO: Can't use isInterface, yet, as it hasn't been updated for the new trait encoding)
val canUseLambdaMetaFactory = (fun.attachments.get[SAMFunction] match {
case Some(SAMFunction(userDefinedSamTp, sam, _)) =>
// LambdaMetaFactory cannot mix in trait members for us, or instantiate classes -- only pure interfaces need apply
erasure.compilesToPureInterface(erasure.javaErasure(userDefinedSamTp).typeSymbol) &&
// impl restriction -- we currently use the boxed apply, so not really useful to allow specialized sam types (https://github.com/scala/scala/pull/4971#issuecomment-198119167)
// specialization and LMF are at odds, since LMF implements the single abstract method,
// but that's the one that specialization leaves generic, whereas we need to implement the specialized one to avoid boxing
!specializeTypes.isSpecializedIn(sam, userDefinedSamTp)
case _ => true // our built-in FunctionN's are suitable for LambdaMetaFactory by construction
})
!canUseLambdaMetaFactory
}
/** 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)
// 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 =>
reporter.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)
&& !(tree.symbol.hasPackageFlag || tree.isInstanceOf[This] || tree.isInstanceOf[Super])
&& 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 :: Nil)
/** 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(nme.NON_LOCAL_RETURN_KEY_STRING), 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(_, catches, _) <- body
cdef <- catches
if catchesThrowable(cdef) && !isSyntheticCase(cdef)
} {
runReporting.warning(body.pos, "catch block may intercept non-local return from " + meth, WarningCategory.Other, meth)
}
Block(List(keyDef), tryCatch)
}
}
// ------ Transforming anonymous functions and by-name-arguments ----------------
/** 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 =
// Undo eta expansion for parameterless and nullary methods, EXCEPT if `fun` targets a SAM.
// Normally, we can unwrap `() => cbn` to `cbn` where `cbn` refers to a CBN argument (typically `cbn` is an Ident),
// because we know `cbn` will already be a `Function0` thunk. When we're targeting a SAM,
// the types don't align and we must preserve the function wrapper.
if (fun.vparams.isEmpty && isByNameRef(fun.body) && fun.attachments.get[SAMFunction].isEmpty) { noApply += fun.body ; fun.body }
else if (forceExpandFunction || inConstructorFlag != 0) {
// Expand the function body into an anonymous class
gen.expandFunction(localTyper)(fun, inConstructorFlag)
} else {
val mustExpand = mustExpandFunction(fun)
// method definition with the same arguments, return type, and body as the original lambda
val liftedMethod = gen.mkLiftedFunctionBodyMethod(localTyper)(fun.symbol.owner, fun)
// new function whose body is just a call to the lifted method
val newFun = deriveFunction(fun)(_ => localTyper.typedPos(fun.pos)(
gen.mkForwarder(gen.mkAttributedRef(liftedMethod.symbol), (fun.vparams map (_.symbol)) :: Nil)
))
if (!mustExpand) {
liftedMethod.symbol.updateAttachment(DelambdafyTarget)
liftedMethod.updateAttachment(DelambdafyTarget)
}
val typedNewFun = localTyper.typedPos(fun.pos)(Block(liftedMethod :: Nil, super.transform(newFun)))
if (mustExpand) {
val Block(stats, expr : Function) = typedNewFun: @unchecked
treeCopy.Block(typedNewFun, stats, gen.expandFunction(localTyper)(expr, inConstructorFlag))
} else {
typedNewFun
}
}
def transformArgs(pos: Position, fun: Symbol, args: List[Tree], params: List[Symbol]): List[Tree] = {
val isJava = fun.isJavaDefined
def transformVarargs(varargsElemType: Type): List[Tree] = {
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, copy: Boolean): Tree = {
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)
if(copy) {
runReporting.deprecationWarning(tree.pos, NoSymbol, currentOwner,
"Passing an explicit array value to a Scala varargs method is deprecated (since 2.13.0) and will result in a defensive copy; "+
"Use the more efficient non-copying ArraySeq.unsafeWrapArray or an explicit toIndexedSeq call", "2.13.0")
gen.mkMethodCall(PredefModule, nme.copyArrayToImmutableIndexedSeq, List(elemtp), List(adaptedTree))
} else gen.mkWrapVarargsArray(adaptedTree, elemtp)
}
}
}
// when calling into java varargs, make sure it's an array - see bug #1360
def sequenceToArray(tree: Tree): Tree = {
val toArraySym = tree.tpe member nme.toArray
assert(toArraySym != NoSymbol, "toArray")
@tailrec
def getClassTag(tp: Type): Tree = {
val tag = localTyper.resolveClassTag(tree.pos, tp)
// Don't want bottom types getting any further than this (scala/bug#4024)
if (tp.typeSymbol.isBottomClass) getClassTag(AnyTpe)
else if (!tag.isEmpty) tag
else if (tp.upperBound ne tp) getClassTag(tp.upperBound)
else localTyper.TyperErrorGen.MissingClassTagError(tree, tp)
}
def iterableClassTag(tpe: Type): Tree = {
(tpe baseType IterableClass).typeArgs match {
case targ :: _ => getClassTag(targ)
case _ => EmptyTree
}
}
exitingUncurry {
localTyper.typedPos(pos) {
gen.mkMethodCall(tree, toArraySym, Nil, List(iterableClassTag(tree.tpe)))
}
}
}
/* Java-style varargs = expects `Array` rather than `Seq`
* Note that `fun.isJavaDefined` is not good enough because
* if we override a varargs method defined in Java, `superaccessors`
* will make us a superaccessor which also takes `Array` rather than `Seq`.
* See scala/bug#10368 */
val javaStyleVarArgs = isJavaVarArgsMethod(fun)
var suffix: Tree =
if (treeInfo isWildcardStarArgList args) {
val Typed(tree, _) = args.last: @unchecked
if (javaStyleVarArgs)
if (tree.tpe.typeSymbol == ArrayClass) tree
else sequenceToArray(tree)
else
if (tree.tpe.typeSymbol isSubClass SeqClass) tree
else arrayToSequence(tree, varargsElemType, copy = true) // existing array, make a defensive copy
}
else {
def mkArray = mkArrayValue(args drop (params.length - 1), varargsElemType)
// if args.length < params.length the repeated argument is empty
def emptyVarargs = compareLengths(args, params) < 0
if (javaStyleVarArgs) mkArray
else if (emptyVarargs) gen.mkNil // avoid needlessly double-wrapping an empty argument list
else arrayToSequence(mkArray, varargsElemType, copy = false) // fresh array, no need to copy
}
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))
}
}
}
val args1 = ListBuffer[Tree]()
args1 ++= args.iterator.take(params.length - 1)
args1 += suffix setType params.last.info
args1.toList
}
val isVarargs = isVarArgsList(params)
val args1 = if (isVarargs) transformVarargs(params.last.info.typeArgs.head.widen) else args
map2Conserve(args1, params) { (arg, param) =>
if (!isByNameParamType(param.info)) arg
else if (isByNameRef(arg)) { // thunk does not need to be forced because it's a reference to a by-name arg passed to a by-name param
byNameArgs += arg
arg setType functionType(Nil, arg.tpe)
} else {
log(s"Argument '$arg' at line ${arg.pos.line} is ${param.info} from ${fun.fullName}")
def canUseDirectly(qual: Tree) = qual.tpe.typeSymbol.isSubClass(FunctionClass(0)) && treeInfo.isExprSafeToInline(qual)
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(qual, nme.apply), Nil) if canUseDirectly(qual) => qual
case body =>
val thunkFun = localTyper.typedPos(body.pos)(Function(Nil, body)).asInstanceOf[Function]
log(s"Change owner from $currentOwner to ${thunkFun.symbol} in ${thunkFun.body}")
thunkFun.body.changeOwner(currentOwner, thunkFun.symbol)
transformFunction(thunkFun)
}
}
}
}
/** 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 = {
def elisionOf(t: Type): Tree = t.typeSymbol match {
case StringClass => Literal(Constant("")) setType t
case _ => gen.mkZero(t)
}
tree match {
case DefDef(_,_,_,_,_,rhs) =>
val rhs1 = if (rhs == EmptyTree) rhs else Block(Nil, elisionOf(rhs.tpe)) setType rhs.tpe
deriveDefDef(tree)(_ => rhs1) setSymbol tree.symbol setType tree.tpe
case _ =>
elisionOf(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 &&
!ddef.symbol.isDelambdafyTarget /* these become static later, unsuitable for ACC_SYNCHRONIZED */
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.
*
* Delambdafy targets are deemed ineligible as the Delambdafy phase will
* replace `this.synchronized` with `\$this.synchronized` now that it emits
* all lambda impl methods as static.
*/
private def translateSynchronized(tree: Tree) = tree match {
case dd @ DefDef(_, _, _, _, _, Apply(_, 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(nme.LIFTED_TREE), tree.pos, Flag.ARTIFACT)
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 target is a lambda body that's been lifted into a method
def isLiftedLambdaMethod(funSym: Symbol) =
funSym.isArtifact && funSym.name.containsName(nme.ANON_FUN_NAME) && funSym.isLocalToBlock
def checkIsElidable(sym: Symbol): Boolean = (sym ne null) && sym.elisionLevel.exists { level =>
if (sym.isMethod) level < settings.elidebelow.value
else {
// TODO: report error? It's already done in RefChecks. https://github.com/scala/scala/pull/5539#issuecomment-331376887
reporter.error(sym.pos, s"${sym.name}: Only methods can be marked @elidable.")
false
}
}
val result =
if (checkIsElidable(sym))
replaceElidableTree(tree)
else translateSynchronized(tree) match {
case dd @ DefDef(mods, name, tparams, _, tpt, rhs) =>
// Remove default argument trees from parameter ValDefs, scala/bug#4812
val vparamssNoRhs = dd.vparamss mapConserve (_ mapConserve {p =>
treeCopy.ValDef(p, p.mods, p.name, p.tpt, EmptyTree)
})
if (dd.symbol hasAnnotation VarargsClass) validateVarargs(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(mods, _, _, rhs) =>
if (sym eq NoSymbol) throw new IllegalStateException("Encountered Valdef without symbol: "+ tree + " in "+ unit)
if (!sym.owner.isSourceMethod || mods.isLazy)
withNeedLift(needLift = true) { super.transform(tree) }
else
super.transform(tree)
case sel: Select if sel.qualifier.tpe.typeSymbol.isDerivedValueClass =>
// `c.f` where `c` is a value class is translated to `C.f$extension(c)` (value class member) or
// `new C(c).f()` (universal trait member). In both cases, `try` within `c` needs a lift.
withNeedLift(needLift = true) { super.transform(tree) }
case Apply(fn, args) =>
// Read the param symbols before `transform(fn)`, because UnCurry replaces T* by Seq[T] (see DesugaredParameterType).
// The call to `transformArgs` below needs `formals` that still have varargs.
val fnParams = fn.tpe.params
val transformedFn = transform(fn)
// scala/bug#6479: no need to lift in args to label jumps
// scala/bug#11127: boolean && / || are emitted using jumps, the lhs stack value is consumed by the conditional jump
val noReceiverOnStack = fn.symbol.isLabel || fn.symbol == currentRun.runDefinitions.Boolean_and || fn.symbol == currentRun.runDefinitions.Boolean_or
val needLift = needTryLift || !noReceiverOnStack
withNeedLift(needLift) {
treeCopy.Apply(tree, transformedFn, transformTrees(transformArgs(tree.pos, fn.symbol, args, fnParams)))
}
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 !forceExpandFunction && isLiftedLambdaMethod(target.symbol) =>
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
}
result.setType(uncurry(result.tpe))
}
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)
}
val sym = tree.symbol
// our info transformer may not have run yet, so duplicate flag logic instead of forcing it to run
val isMethodExitingUncurry = (sym hasFlag METHOD) || (sym hasFlag MODULE) && !sym.isStatic
if (isMethodExitingUncurry && !tree.tpe.isInstanceOf[PolyType])
gen.mkApplyIfNeeded(removeNullary()) // apply () if tree.tpe has zero-arg MethodType
else if (tree.isType)
TypeTree(tree.tpe) setPos tree.pos
else
tree
}
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 ddSym = dd.symbol
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)
}
// A no-arg method with ConstantType result type can safely be reduced to the corresponding Literal
// (only pure methods are typed as ConstantType). We could also do this for methods with arguments,
// after ensuring the arguments are not referenced.
val literalRhsIfConst =
if (newParamss.head.isEmpty) { // We know newParamss.length == 1 from above
ddSym.info.resultType match {
case tp@FoldableConstantType(value) => Literal(value) setType tp setPos newRhs.pos // inlining of gen.mkAttributedQualifier(tp)
case _ => newRhs
}
} else newRhs
val flatdd = copyDefDef(dd)(
vparamss = newParamss,
rhs = nonLocalReturnKeys get ddSym match {
case Some(k) => atPos(newRhs.pos)(nonLocalReturnTry(literalRhsIfConst, k, ddSym))
case None => literalRhsIfConst
}
)
// Only class members can reasonably be called from Java due to name mangling.
// Additionally, the Uncurry info transformer only adds a forwarder symbol to class members,
// since the other symbols are not part of the ClassInfoType (see reflect.internal.transform.UnCurry)
if (dd.symbol.owner.isClass)
addJavaVarargsForwarders(dd, flatdd)
else
flatdd
case tree: Try =>
devWarningIf(tree.catches exists (!treeInfo.isCatchCase(_))) {
"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(s"non-local return from ${currentOwner.enclMethod} to ${ret.symbol}")
if (settings.warnNonlocalReturn)
runReporting.warning(ret.pos, s"return statement uses an exception to pass control to the caller of the enclosing named ${ret.symbol}", WarningCategory.LintNonlocalReturn, 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. (scala/bug#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 `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 {
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.{rhs, vparamss}
val (allParams, packedParamsSyms, tempVals): (List[ValDef], List[Symbol], List[ValDef]) = {
val allParamsBuf: ListBuffer[ValDef] = ListBuffer.empty
val packedParamsSymsBuf: ListBuffer[Symbol] = ListBuffer.empty
val tempValsBuf: ListBuffer[ValDef] = ListBuffer.empty
def addPacked(param: ValDef, tempVal: ValDef): Unit = {
allParamsBuf += param
if (rhs != EmptyTree) {
packedParamsSymsBuf += param.symbol
tempValsBuf += tempVal
}
}
def addParamTransform(p: ValDef, infoParam: Symbol): Unit = {
val packedType = infoParam.info
if (packedType =:= p.symbol.info) allParamsBuf += 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 = {
// scala/bug#9442: using the "uncurry-erased" type (the one after the uncurry phase) can lead to incorrect
// tree transformations. For example, compiling:
//
// def foo(c: Ctx)(l: c.Tree): Unit = {
// val l2: c.Tree = l
// }
//
// Results in the following AST:
//
// def foo(c: Ctx, l: Ctx#Tree): Unit = {
// val l$1: Ctx#Tree = l.asInstanceOf[Ctx#Tree]
// val l2: c.Tree = l$1 // no, not really, it's not.
// }
//
// Of course, this is incorrect, since `l$1` has type `Ctx#Tree`, which is not a subtype of `c.Tree`.
//
// So what we need to do is to use the pre-uncurry type when creating `l$1`, which is `c.Tree` and is
// correct. Now, there are two additional problems:
// 1. when varargs and byname params are involved, the uncurry transformation desugars these special
// cases to actual typerefs, eg:
//
// T* ~> Seq[T] (Scala-defined varargs)
// T* ~> Array[T] (Java-defined varargs)
// => T ~> Function0[T] (by name params)
//
// we use the DesugaredParameterType object (defined in scala.reflect.internal.transform.UnCurry)
// to redo this desugaring manually here
// 2. the type needs to be normalized, since `gen.mkCast` checks this (no HK here, just aliases have
// to be expanded before handing the type to `gen.mkAttributedCast`, which calls `gen.mkCast`)
val info0 =
enteringUncurry(p.symbol.info) match {
case DesugaredParameterType(desugaredTpe) =>
desugaredTpe
case tpe =>
tpe
}
val info = info0.normalize
val tempValName = unit.freshTermName(p.name.toStringWithSuffix("$"))
val newSym = dd.symbol.newTermSymbol(tempValName, p.pos, SYNTHETIC).setInfo(info)
atPos(p.pos)(ValDef(newSym, gen.mkAttributedCast(Ident(p.symbol), info)))
}
addPacked(newParam, tempVal)
}
}
val viter = vparamss.iterator.flatten
val piter = dd.symbol.info.paramss.iterator.flatten
while (viter.hasNext && piter.hasNext)
addParamTransform(viter.next(), piter.next())
(allParamsBuf.toList, packedParamsSymsBuf.toList, tempValsBuf.toList)
}
val rhs1 = if (rhs == EmptyTree || tempVals.isEmpty) rhs else {
localTyper.typedPos(rhs.pos) {
// Patch the method body to refer to the temp vals
val rhsSubstituted = rhs.substituteSymbols(packedParamsSyms, tempVals.map(_.symbol))
// The new method body: { val p$1 = p.asInstanceOf[]; ...; }
Block(tempVals, rhsSubstituted)
}
}
(allParams :: Nil, rhs1)
}
}
private def validateVarargs(dd: DefDef): Unit =
if (dd.symbol.isConstructor)
reporter.error(dd.symbol.pos, "A constructor cannot be annotated with a `varargs` annotation.")
else {
val ok = cond(dd.symbol.paramss.filter(_.nonEmpty)) {
case initPs :+ lastPs =>
initPs.forall(!definitions.isVarArgsList(_)) && definitions.isVarArgsList(lastPs)
}
if (!ok)
reporter.error(dd.pos, "A method annotated with @varargs must have a single repeated parameter in its last parameter list.")
}
/**
* Called during post transform, after the method argument lists have been flattened.
* It looks for the forwarder symbol in the symbol attachments and generates a Java-style
* varargs forwarder.
*
* @note The Java-style varargs method symbol is generated in the Uncurry info transformer. If the
* symbol can't be found this method reports a warning and carries on.
* @see [[scala.reflect.internal.transform.UnCurry]]
*/
private def addJavaVarargsForwarders(dd: DefDef, flatdd: DefDef): DefDef = {
if (!dd.symbol.hasAnnotation(VarargsClass) || !enteringUncurry(mexists(dd.symbol.paramss)(sym => definitions.isRepeatedParamType(sym.tpe))))
return flatdd
val forwSym: Symbol = {
currentClass.info // make sure the info is up to date, so the varargs forwarder symbol has been generated
flatdd.symbol.attachments.get[VarargsSymbolAttachment] match {
case Some(VarargsSymbolAttachment(sym)) => sym
case None =>
runReporting.warning(dd.pos, s"Could not generate Java varargs forwarder for ${flatdd.symbol}. Please file a bug.", WarningCategory.Other, dd.symbol)
return flatdd
}
}
val newPs = forwSym.tpe.params
val isRepeated = enteringUncurry(dd.symbol.info.paramss.flatten.map(sym => definitions.isRepeatedParamType(sym.tpe)))
val oldPs = flatdd.symbol.paramss.head
val theTyper = typer.atOwner(dd, currentClass)
val forwTree = theTyper.typedPos(dd.pos) {
val seqArgs = map3(newPs, oldPs, isRepeated)((param, _, isRep) => {
if (!isRep) Ident(param)
else {
val parTp = elementType(ArrayClass, param.tpe)
val wrap = gen.mkWrapVarargsArray(Ident(param), parTp)
param.attachments.get[TypeParamVarargsAttachment] match {
case Some(TypeParamVarargsAttachment(tp)) => gen.mkCast(wrap, seqType(tp))
case _ => wrap
}
}
})
val forwCall = Apply(gen.mkAttributedRef(flatdd.symbol), seqArgs)
DefDef(forwSym, if (forwSym.isConstructor) Block(List(forwCall), UNIT) else forwCall)
}
// check if the method with that name and those arguments already exists in the template
enteringUncurry(currentClass.info.member(forwSym.name).alternatives.find(s => s != forwSym && s.tpe.matches(forwSym.tpe))) match {
case Some(s) =>
reporter.error(dd.symbol.pos,
s"A method annotated with @varargs produces a forwarder method with the same signature ${s.tpe} as an existing method.")
case None =>
// enter symbol into scope
addNewMember(forwTree)
}
flatdd
}
}
}
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