package dotty.tools.dotc
package transform
import TreeTransforms._
import core.Denotations._
import core.SymDenotations._
import core.Contexts._
import core.Symbols._
import core.Types._
import core.Constants._
import core.StdNames._
import core.transform.Erasure.isUnboundedGeneric
import dotty.tools.dotc.ast.tpd
import dotty.tools.dotc.util.Positions
import typer.ErrorReporting._
import ast.Trees._
import dotty.tools.dotc.util.Positions.Position
import dotty.tools.dotc.core.Decorators._
import dotty.tools.dotc.core.Flags
import scala.reflect.internal.util.Collections
/** This transform eliminates patterns. Right now it's a dummy.
* Awaiting the real pattern matcher.
* elimRepeated is required
*/
class PatternMatcher extends MiniPhaseTransform {
import dotty.tools.dotc.ast.tpd._
implicit val ctx: Context = ???
def name: String = "patternMatcher"
/*override def transformCaseDef(tree: CaseDef)(implicit ctx: Context, info: TransformerInfo): Tree =
cpy.CaseDef(tree, Literal(Constant("<eliminated pattern>")), tree.guard, tree.body)*/
/*case Try(block, catches, finalizer) =>
treeCopy.Try(tree, transform(block), translator.translateTry(transformTrees(catches).asInstanceOf[List[CaseDef]], tree.tpe, tree.pos), transform(finalizer))
case _ => super.transform(tree)*/
/*override def transformMatch(tree: tpd.Match)(implicit ctx: Context, info: TransformerInfo): tpd.Tree = {
case Match(sel, cases) =>
val origTp = tree.tpe
// setType origTp intended for CPS -- TODO: is it necessary?
val translated = translator.translateMatch(treeCopy.Match(tree, transform(sel), transformTrees(cases).asInstanceOf[List[CaseDef]]))
try {
localTyper.typed(translated) setType origTp
} catch {
case x: (Types#TypeError) =>
// TODO: this should never happen; error should've been reported during type checking
unit.error(tree.pos, "error during expansion of this match (this is a scalac bug).\nThe underlying error was: "+ x.msg)
translated
}
}*/
def translator = {
new OptimizingMatchTranslator/*(localTyper)*/
}
class OptimizingMatchTranslator extends MatchOptimizer/*(val typer: analyzer.Typer)*/ /*extends MatchTranslator*/
trait Debugging {
// TODO: the inliner fails to inline the closures to debug.patmat unless the method is nested in an object
object debug {
//val printPatmat = global.settings.Ypatmatdebug.value
final def patmat(s: => String) = /*if (printPatmat) Console.err.*/
println(s)
final def patmatResult[T](s: => String)(result: T): T = {
/*if (printPatmat) Console.err.*/
println(s + ": " + result)
result
}
}
}
trait MatchMonadInterface {
// val typer: Typer
def matchOwner(implicit ctx: Context) = ctx.owner
def pureType(tp: Type): Type = tp
def reportUnreachable(pos: Position) = {
ctx.warning("unreachable code", pos)
}
def reportMissingCases(pos: Position, counterExamples: List[String]) = {
val ceString =
if (counterExamples.tail.isEmpty) "input: " + counterExamples.head
else "inputs: " + counterExamples.mkString(", ")
ctx.warning("match may not be exhaustive.\nIt would fail on the following "+ ceString, pos)
}
}
trait CodegenCore extends MatchMonadInterface {
private var ctr = 0
def freshName(prefix: String) = ctx.freshName(prefix).toTermName
// assert(owner ne null); assert(owner ne NoSymbol)
def freshSym(pos: Position, tp: Type = NoType, prefix: String = "x") =
ctx.newSymbol(ctx.owner, freshName(prefix), Flags.Synthetic, tp, coord = pos)
def newSynthCaseLabel(name: String, tpe:Type) = ctx.newSymbol(ctx.owner, ctx.freshName(name).toTermName, Flags.Label, tpe)
//NoSymbol.newLabel(freshName(name), NoPosition) setFlag treeInfo.SYNTH_CASE_FLAGS
// codegen relevant to the structure of the translation (how extractors are combined)
trait AbsCodegen {
def matcher(scrut: Tree, scrutSym: Symbol, restpe: Type)(cases: List[Casegen => Tree], matchFailGen: Option[Symbol => Tree]): Tree
// local / context-free
def _asInstanceOf(b: Symbol, tp: Type): Tree
def _equals(checker: Tree, binder: Symbol): Tree
def _isInstanceOf(b: Symbol, tp: Type): Tree
def drop(tgt: Tree)(n: Int): Tree
def index(tgt: Tree)(i: Int): Tree
def mkZero(tp: Type): Tree
def tupleSel(binder: Symbol)(i: Int): Tree
}
// structure
trait Casegen extends AbsCodegen {
def one(res: Tree): Tree
def flatMap(prev: Tree, b: Symbol, next: Tree): Tree
def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree
def flatMapGuard(cond: Tree, next: Tree): Tree
def ifThenElseZero(c: Tree, thenp: Tree): Tree =
If(c, thenp, zero)
protected def zero: Tree
}
def codegen: AbsCodegen
abstract class CommonCodegen extends AbsCodegen {
def fun(arg: TermSymbol, body: Tree): Tree =
DefDef(arg, body)
def tupleSel(binder: Symbol)(i: Int): Tree = ref(binder).select(nme.productAccessorName(i)) // make tree that accesses the i'th component of the tuple referenced by binder
def index(tgt: Tree)(i: Int): Tree = tgt.appliedTo(Literal(Constant(i)))
// Right now this blindly calls drop on the result of the unapplySeq
// unless it verifiably has no drop method (this is the case in particular
// with Array.) You should not actually have to write a method called drop
// for name-based matching, but this was an expedient route for the basics.
def drop(tgt: Tree)(n: Int): Tree = {
def callDirect = tgt.select(nme.drop).appliedTo(Literal(Constant(n)))
def callRuntime = ref(ctx.definitions.traversableDropMethod).appliedTo(tgt, Literal(Constant(n)))
def needsRuntime = (tgt.tpe ne null) && tgt.tpe.baseTypeRef(ctx.definitions.SeqType.classSymbol).member(nme.drop).exists /*typeOfMemberNamedDrop(tgt.tpe) == NoType*/
if (needsRuntime) callRuntime else callDirect
}
// NOTE: checker must be the target of the ==, that's the patmat semantics for ya
def _equals(checker: Tree, binder: Symbol): Tree = checker.select(defn.Any_equals).appliedTo(ref(binder))
// the force is needed mainly to deal with the GADT typing hack (we can't detect it otherwise as tp nor pt need contain an abstract type, we're just casting wildly)
def _asInstanceOf(b: Symbol, tp: Type): Tree = if (b.info <:< tp) ref(b) else ref(b).select(defn.Any_asInstanceOf).appliedToType(tp)
def _isInstanceOf(b: Symbol, tp: Type): Tree = ref(b).select(defn.Any_isInstanceOf).appliedToType(tp)
def mkZero(tp: Type): Tree = initValue(tp)
}
}
trait TypedSubstitution extends MatchMonadInterface {
object Substitution {
def apply(from: Symbol, to: Tree) = new Substitution(List(from), List(to))
// requires sameLength(from, to)
def apply(from: List[Symbol], to: List[Tree]) =
if (from nonEmpty) new Substitution(from, to) else EmptySubstitution
}
class Substitution(val from: List[Symbol], val to: List[Tree]) {
// We must explicitly type the trees that we replace inside some other tree, since the latter may already have been typed,
// and will thus not be retyped. This means we might end up with untyped subtrees inside bigger, typed trees.
def apply(tree: Tree): Tree = {
// according to -Ystatistics 10% of translateMatch's time is spent in this method...
// since about half of the typedSubst's end up being no-ops, the check below shaves off 5% of the time spent in typedSubst
/*if (!tree.exists { case i@Ident(_) => from contains i.symbol case _ => false}) tree
else*/ (new TreeMap {
/*private def typedIfOrigTyped(to: Tree, origTp: Type): Tree =
if (origTp == null || origTp == NoType) to
// important: only type when actually substing and when original tree was typed
// (don't need to use origTp as the expected type, though, and can't always do this anyway due to unknown type params stemming from polymorphic extractors)
else typer.typed(to)*/
override def transform(tree: Tree)(implicit ctx: Context): Tree = {
def subst(from: List[Symbol], to: List[Tree]): Tree =
if (from.isEmpty) tree
else if (tree.symbol == from.head) to.head //typedIfOrigTyped(to.head.shallowDuplicate.setPos(tree.pos), tree.tpe)
else subst(from.tail, to.tail)
tree match {
case Ident(_) => subst(from, to)
case _ => super.transform(tree)
}
}
}).transform(tree)
}
// the substitution that chains `other` before `this` substitution
// forall t: Tree. this(other(t)) == (this >> other)(t)
def >>(other: Substitution): Substitution = {
val (fromFiltered, toFiltered) = (from, to).zipped filter { (f, t) => !other.from.contains(f) }
new Substitution(other.from ++ fromFiltered, other.to.map(apply) ++ toFiltered) // a quick benchmarking run indicates the `.map(apply)` is not too costly
}
override def toString = (from.map(_.name) zip to) mkString("Substitution(", ", ", ")")
}
object EmptySubstitution extends Substitution(Nil, Nil) {
override def apply(tree: Tree): Tree = tree
override def >>(other: Substitution): Substitution = other
}
}
trait OptimizedCodegen extends CodegenCore with TypedSubstitution with MatchMonadInterface {
override def codegen: AbsCodegen = optimizedCodegen
// when we know we're targetting Option, do some inlining the optimizer won't do
// for example, `o.flatMap(f)` becomes `if(o == None) None else f(o.get)`, similarly for orElse and guard
// this is a special instance of the advanced inlining optimization that takes a method call on
// an object of a type that only has two concrete subclasses, and inlines both bodies, guarded by an if to distinguish the two cases
object optimizedCodegen extends CommonCodegen { //import CODE._
/** Inline runOrElse and get rid of Option allocations
*
* runOrElse(scrut: scrutTp)(matcher): resTp = matcher(scrut) getOrElse ${catchAll(`scrut`)}
* the matcher's optional result is encoded as a flag, keepGoing, where keepGoing == true encodes result.isEmpty,
* if keepGoing is false, the result Some(x) of the naive translation is encoded as matchRes == x
*/
def matcher(scrut: Tree, scrutSym: Symbol, restpe: Type)(cases: List[Casegen => Tree], matchFailGen: Option[Symbol => Tree]): Tree = {
val matchRes = ctx.newSymbol(NoSymbol, ctx.freshName("x").toTermName, Flags.Synthetic | Flags.Param, restpe /*withoutAnnotations*/)
//NoSymbol.newValueParameter(newTermName("x"), NoPosition, newFlags = SYNTHETIC) setInfo restpe.withoutAnnotations
val mtype = MethodType(List("x".toTermName), List(restpe))(_=>restpe)
val matchEnd = newSynthCaseLabel("matchEnd", mtype)
val matchEndDef = DefDef(matchEnd, args => args.head.head)
var lastSymbol: TermSymbol = null
def newCaseSym = {
lastSymbol = newSynthCaseLabel(ctx.freshName("case"), MethodType(Nil, restpe))
lastSymbol
}
// must compute catchAll after caseLabels (side-effects nextCase)
// catchAll.isEmpty iff no synthetic default case needed (the (last) user-defined case is a default)
// if the last user-defined case is a default, it will never jump to the next case; it will go immediately to matchEnd
val catchAllDef = matchFailGen.map({ matchFailGen =>
DefDef(newCaseSym, _ => Block(List(matchEndDef), ref(matchEnd).appliedTo(matchFailGen(scrutSym))))
}) // at most 1 element
val caseDefs = cases.foldLeft[Tree](catchAllDef.getOrElse(matchEndDef)){ (acc: Tree, mkCase: Casegen => Tree) =>
val nextCase = lastSymbol.orElse(matchEnd)
DefDef(newCaseSym, _ => Block(List(acc), mkCase(new OptimizedCasegen(matchEnd, nextCase))))
}
// scrutSym == NoSymbol when generating an alternatives matcher
// val scrutDef = scrutSym.fold(List[Tree]())(ValDef(_, scrut) :: Nil) // for alternatives
// the generated block is taken apart in TailCalls under the following assumptions
// the assumption is once we encounter a case, the remainder of the block will consist of cases
// the prologue may be empty, usually it is the valdef that stores the scrut
// val (prologue, cases) = stats span (s => !s.isInstanceOf[LabelDef])
Block(
List(caseDefs),
ref(lastSymbol).appliedToNone
)
}
class OptimizedCasegen(matchEnd: Symbol, nextCase: Symbol) extends CommonCodegen with Casegen {
def matcher(scrut: Tree, scrutSym: Symbol, restpe: Type)(cases: List[Casegen => Tree], matchFailGen: Option[Symbol => Tree]): Tree =
optimizedCodegen.matcher(scrut, scrutSym, restpe)(cases, matchFailGen)
// only used to wrap the RHS of a body
// res: T
// returns MatchMonad[T]
def one(res: Tree): Tree = ref(matchEnd) appliedTo res // a jump to a case label is special-cased in typedApply
protected def zero: Tree = ref(nextCase) appliedToNone
// prev: MatchMonad[T]
// b: T
// next: MatchMonad[U]
// returns MatchMonad[U]
def flatMap(prev: Tree, b: Symbol, next: Tree): Tree = {
val prevSym = freshSym(prev.pos, prev.tpe, "o")
Block(
List(ValDef(prevSym, prev)),
// must be isEmpty and get as we don't control the target of the call (prev is an extractor call)
ifThenElseZero(
ref(prevSym).select("isEmpty".toTermName).select(ctx.definitions.Boolean_!),
Substitution(b, ref(prevSym).select("get".toTermName))(next)
)
)
}
// cond: Boolean
// res: T
// nextBinder: T
// next == MatchMonad[U]
// returns MatchMonad[U]
def flatMapCond(cond: Tree, res: Tree, nextBinder: Symbol, next: Tree): Tree = {
val rest = Block(List(ValDef(nextBinder.asTerm, res)), next)
ifThenElseZero(cond, rest)
}
// guardTree: Boolean
// next: MatchMonad[T]
// returns MatchMonad[T]
def flatMapGuard(guardTree: Tree, next: Tree): Tree =
ifThenElseZero(guardTree, next)
def flatMapCondStored(cond: Tree, condSym: Symbol, res: Tree, nextBinder: Symbol, next: Tree): Tree =
ifThenElseZero(cond, Block(
List(Assign(ref(condSym), Literal(Constant(true))),
Assign(ref(nextBinder), res)),
next
))
}
}
}
final case class Suppression(exhaustive: Boolean, unreachable: Boolean)
object Suppression {
val NoSuppression = Suppression(false, false)
}
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// the making of the trees
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
trait TreeMakers extends TypedSubstitution with CodegenCore {
def optimizeCases(prevBinder: Symbol, cases: List[List[TreeMaker]], pt: Type): (List[List[TreeMaker]], List[Tree])
def analyzeCases(prevBinder: Symbol, cases: List[List[TreeMaker]], pt: Type, suppression: Suppression): Unit
def emitSwitch(scrut: Tree, scrutSym: Symbol, cases: List[List[TreeMaker]], pt: Type, matchFailGenOverride: Option[Symbol => Tree], unchecked: Boolean): Option[Tree] =
None
// for catch (no need to customize match failure)
def emitTypeSwitch(bindersAndCases: List[(Symbol, List[TreeMaker])], pt: Type): Option[List[CaseDef]] =
None
abstract class TreeMaker{
def pos: Position
/** captures the scope and the value of the bindings in patterns
* important *when* the substitution happens (can't accumulate and do at once after the full matcher has been constructed)
*/
def substitution: Substitution =
if (currSub eq null) localSubstitution
else currSub
protected def localSubstitution: Substitution
private[TreeMakers] def incorporateOuterSubstitution(outerSubst: Substitution): Unit = {
if (currSub ne null) {
println("BUG: incorporateOuterSubstitution called more than once for "+ ((this, currSub, outerSubst)))
Thread.dumpStack()
}
else currSub = outerSubst >> substitution
}
private[this] var currSub: Substitution = null
/** The substitution that specifies the trees that compute the values of the subpattern binders.
*
* Should not be used to perform actual substitution!
* Only used to reason symbolically about the values the subpattern binders are bound to.
* See TreeMakerToCond#updateSubstitution.
*
* Overridden in PreserveSubPatBinders to pretend it replaces the subpattern binders by subpattern refs
* (Even though we don't do so anymore -- see SI-5158, SI-5739 and SI-6070.)
*
* TODO: clean this up, would be nicer to have some higher-level way to compute
* the binders bound by this tree maker and the symbolic values that correspond to them
*/
def subPatternsAsSubstitution: Substitution = substitution
// build Tree that chains `next` after the current extractor
def chainBefore(next: Tree)(casegen: Casegen): Tree
}
sealed trait NoNewBinders extends TreeMaker {
protected val localSubstitution: Substitution = EmptySubstitution
}
case class TrivialTreeMaker(tree: Tree) extends TreeMaker with NoNewBinders {
def pos = tree.pos
def chainBefore(next: Tree)(casegen: Casegen): Tree = tree
}
case class BodyTreeMaker(body: Tree, matchPt: Type) extends TreeMaker with NoNewBinders {
def pos = body.pos
def chainBefore(next: Tree)(casegen: Casegen): Tree = // assert(next eq EmptyTree)
/*atPos(body.pos)*/(casegen.one(/*substitution(*/body/*)*/)) // since SubstOnly treemakers are dropped, need to do it here
override def toString = "B"+((body, matchPt))
}
case class SubstOnlyTreeMaker(prevBinder: Symbol, nextBinder: Symbol) extends TreeMaker {
val pos = Positions.NoPosition
val localSubstitution = Substitution(prevBinder, ref(nextBinder))
def chainBefore(next: Tree)(casegen: Casegen): Tree = /*substitution(*/next//)
override def toString = "S" + localSubstitution
}
sealed abstract class FunTreeMaker extends TreeMaker {
val nextBinder: Symbol
def pos = nextBinder.pos
}
sealed abstract class CondTreeMaker extends FunTreeMaker {
val prevBinder: Symbol
val nextBinderTp: Type
val cond: Tree
val res: Tree
lazy val nextBinder = freshSym(pos, nextBinderTp)
lazy val localSubstitution = Substitution(List(prevBinder), List(ref(nextBinder)))
def chainBefore(next: Tree)(casegen: Casegen): Tree =
/*atPos(pos)(*/casegen.flatMapCond(cond, res, nextBinder, substitution(next))//)
}
// unless we're optimizing, emit local variable bindings for all subpatterns of extractor/case class patterns
protected val debugInfoEmitVars = true //!settings.optimise.value
sealed trait PreserveSubPatBinders extends TreeMaker {
val subPatBinders: List[Symbol]
val subPatRefs: List[Tree]
val ignoredSubPatBinders: Set[Symbol]
// unless `debugInfoEmitVars`, this set should contain the bare minimum for correctness
// mutable case class fields need to be stored regardless (SI-5158, SI-6070) -- see override in ProductExtractorTreeMaker
// sub patterns bound to wildcard (_) are never stored as they can't be referenced
// dirty debuggers will have to get dirty to see the wildcards
lazy val storedBinders: Set[Symbol] =
(if (debugInfoEmitVars) subPatBinders.toSet else Set.empty) ++ extraStoredBinders -- ignoredSubPatBinders
// e.g., mutable fields of a case class in ProductExtractorTreeMaker
def extraStoredBinders: Set[Symbol]
def emitVars = storedBinders.nonEmpty
private lazy val (stored, substed) = (subPatBinders, subPatRefs).zipped.partition{ case (sym, _) => storedBinders(sym) }
protected lazy val localSubstitution: Substitution = if (!emitVars) Substitution(subPatBinders, subPatRefs)
else {
val (subPatBindersSubstituted, subPatRefsSubstituted) = substed.unzip
Substitution(subPatBindersSubstituted.toList, subPatRefsSubstituted.toList)
}
/** The substitution that specifies the trees that compute the values of the subpattern binders.
*
* We pretend to replace the subpattern binders by subpattern refs
* (Even though we don't do so anymore -- see SI-5158, SI-5739 and SI-6070.)
*/
override def subPatternsAsSubstitution =
Substitution(subPatBinders, subPatRefs) >> super.subPatternsAsSubstitution
def bindSubPats(in: Tree): Tree =
if (!emitVars) in
else {
// binders in `subPatBindersStored` that are referenced by tree `in`
val usedBinders = new collection.mutable.HashSet[Symbol]()
// all potentially stored subpat binders
val potentiallyStoredBinders = stored.unzip._1.toSet
// compute intersection of all symbols in the tree `in` and all potentially stored subpat binders
new DeepFolder[Unit]((x: Unit, t:Tree) => if (potentiallyStoredBinders(t.symbol)) usedBinders += t.symbol).apply((), in)
if (usedBinders.isEmpty) in
else {
// only store binders actually used
val (subPatBindersStored, subPatRefsStored) = stored.filter{case (b, _) => usedBinders(b)}.unzip
Block(Collections.map2(subPatBindersStored.toList, subPatRefsStored.toList)((bind, ref) => ValDef(bind.asTerm, ref)), in)
}
}
}
/**
* Make a TreeMaker that will result in an extractor call specified by `extractor`
* the next TreeMaker (here, we don't know which it'll be) is chained after this one by flatMap'ing
* a function with binder `nextBinder` over our extractor's result
* the function's body is determined by the next TreeMaker
* (furthermore, the interpretation of `flatMap` depends on the codegen instance we're using).
*
* The values for the subpatterns, as computed by the extractor call in `extractor`,
* are stored in local variables that re-use the symbols in `subPatBinders`.
* This makes extractor patterns more debuggable (SI-5739).
*/
case class ExtractorTreeMaker(extractor: Tree, extraCond: Option[Tree], nextBinder: Symbol)(
val subPatBinders: List[Symbol],
val subPatRefs: List[Tree],
extractorReturnsBoolean: Boolean,
val checkedLength: Option[Int],
val prevBinder: Symbol,
val ignoredSubPatBinders: Set[Symbol]
) extends FunTreeMaker with PreserveSubPatBinders {
def extraStoredBinders: Set[Symbol] = Set()
println(s"""
|ExtractorTreeMaker($extractor, $extraCond, $nextBinder) {
| $subPatBinders
| $subPatRefs
| $extractorReturnsBoolean
| $checkedLength
| $prevBinder
| $ignoredSubPatBinders
|}""".stripMargin)
def chainBefore(next: Tree)(casegen: Casegen): Tree = {
val condAndNext = extraCond match {
case Some(cond: Tree) =>
casegen.ifThenElseZero(substitution(cond), bindSubPats(substitution(next)))
case _ =>
bindSubPats(substitution(next))
}
if (extractorReturnsBoolean) casegen.flatMapCond(extractor, unitLiteral, nextBinder, condAndNext)
else casegen.flatMap(extractor, nextBinder, condAndNext)
}
override def toString = "X"+((extractor, nextBinder.name))
}
/**
* An optimized version of ExtractorTreeMaker for Products.
* For now, this is hard-coded to case classes, and we simply extract the case class fields.
*
* The values for the subpatterns, as specified by the case class fields at the time of extraction,
* are stored in local variables that re-use the symbols in `subPatBinders`.
* This makes extractor patterns more debuggable (SI-5739) as well as
* avoiding mutation after the pattern has been matched (SI-5158, SI-6070)
*
* TODO: make this user-definable as follows
* When a companion object defines a method `def unapply_1(x: T): U_1`, but no `def unapply` or `def unapplySeq`,
* the extractor is considered to match any non-null value of type T
* the pattern is expected to have as many sub-patterns as there are `def unapply_I(x: T): U_I` methods,
* and the type of the I'th sub-pattern is `U_I`.
* The same exception for Seq patterns applies: if the last extractor is of type `Seq[U_N]`,
* the pattern must have at least N arguments (exactly N if the last argument is annotated with `: _*`).
* The arguments starting at N (and beyond) are taken from the sequence returned by apply_N,
* and it is checked that that sequence has enough elements to provide values for all expected sub-patterns.
*
* For a case class C, the implementation is assumed to be `def unapply_I(x: C) = x._I`,
* and the extractor call is inlined under that assumption.
*/
case class ProductExtractorTreeMaker(prevBinder: Symbol, extraCond: Option[Tree])(
val subPatBinders: List[Symbol],
val subPatRefs: List[Tree],
val mutableBinders: List[Symbol],
binderKnownNonNull: Boolean,
val ignoredSubPatBinders: Set[Symbol]
) extends FunTreeMaker with PreserveSubPatBinders {
val nextBinder = prevBinder // just passing through
// mutable binders must be stored to avoid unsoundness or seeing mutation of fields after matching (SI-5158, SI-6070)
def extraStoredBinders: Set[Symbol] = mutableBinders.toSet
def chainBefore(next: Tree)(casegen: Casegen): Tree = {
val nullCheck: Tree = ref(prevBinder).select(ctx.definitions.Object_ne).appliedTo(Literal(Constant(null)))
val cond: Option[Tree] =
if (binderKnownNonNull) extraCond
else extraCond.map(nullCheck.select(ctx.definitions.Boolean_and).appliedTo).orElse(Some(nullCheck))
cond match {
case Some(cond: Tree) =>
casegen.ifThenElseZero(cond, bindSubPats(substitution(next)))
case _ =>
bindSubPats(substitution(next))
}
}
override def toString = "P"+((prevBinder.name, extraCond getOrElse "", localSubstitution))
}
object IrrefutableExtractorTreeMaker {
// will an extractor with unapply method of methodtype `tp` always succeed?
// note: this assumes the other side-conditions implied by the extractor are met
// (argument of the right type, length check succeeds for unapplySeq,...)
def irrefutableExtractorType(tp: Type): Boolean = tp.resultType.dealias match {
// case TypeRef(_, SomeClass, _) => true todo
// probably not useful since this type won't be inferred nor can it be written down (yet)
// case ConstantTrue => true todo
case _ => false
}
def unapply(xtm: ExtractorTreeMaker): Option[(Tree, Symbol)] = xtm match {
case ExtractorTreeMaker(extractor, None, nextBinder) if irrefutableExtractorType(extractor.tpe) =>
Some((extractor, nextBinder))
case _ =>
None
}
}
object TypeTestTreeMaker {
// factored out so that we can consistently generate other representations of the tree that implements the test
// (e.g. propositions for exhaustivity and friends, boolean for isPureTypeTest)
trait TypeTestCondStrategy {
type Result
def outerTest(testedBinder: Symbol, expectedTp: Type): Result
// TODO: can probably always widen
def typeTest(testedBinder: Symbol, expectedTp: Type): Result
def nonNullTest(testedBinder: Symbol): Result
def equalsTest(pat: Tree, testedBinder: Symbol): Result
def eqTest(pat: Tree, testedBinder: Symbol): Result
def and(a: Result, b: Result): Result
def tru: Result
}
object treeCondStrategy extends TypeTestCondStrategy {
type Result = Tree
def and(a: Result, b: Result): Result = a.select(ctx.definitions.Boolean_and).appliedTo(b)
def tru = Literal(Constant(true))
def typeTest(testedBinder: Symbol, expectedTp: Type) = codegen._isInstanceOf(testedBinder, expectedTp)
def nonNullTest(testedBinder: Symbol) = ref(testedBinder).select(ctx.definitions.Object_ne).appliedTo(Literal(Constant(null)))
def equalsTest(pat: Tree, testedBinder: Symbol) = codegen._equals(pat, testedBinder)
def eqTest(pat: Tree, testedBinder: Symbol) = ref(testedBinder).select(ctx.definitions.Object_eq).appliedTo(pat)
def outerTest(testedBinder: Symbol, expectedTp: Type): Tree = {
val expectedOuter = expectedTp.normalizedPrefix match {
case ThisType(clazz) => This(clazz)
case NoType => Literal(Constant(true)) // fallback for SI-6183 todo?
case pre => ref(pre.termSymbol)
}
// ExplicitOuter replaces `Select(q, outerSym) OBJ_EQ expectedPrefix` by `Select(q, outerAccessor(outerSym.owner)) OBJ_EQ expectedPrefix`
// if there's an outer accessor, otherwise the condition becomes `true` -- TODO: can we improve needsOuterTest so there's always an outerAccessor?
// val outer = expectedTp.typeSymbol.newMethod(vpmName.outer, newFlags = SYNTHETIC | ARTIFACT) setInfo expectedTp.prefix
codegen._asInstanceOf(testedBinder, expectedTp).select("<outer>".toTermName).select(ctx.definitions.Object_eq).appliedTo(expectedOuter)
}
}
object pureTypeTestChecker extends TypeTestCondStrategy {
type Result = Boolean
def typeTest(testedBinder: Symbol, expectedTp: Type): Result = true
def outerTest(testedBinder: Symbol, expectedTp: Type): Result = false
def nonNullTest(testedBinder: Symbol): Result = false
def equalsTest(pat: Tree, testedBinder: Symbol): Result = false
def eqTest(pat: Tree, testedBinder: Symbol): Result = false
def and(a: Result, b: Result): Result = false // we don't and type tests, so the conjunction must include at least one false
def tru = true
}
def nonNullImpliedByTestChecker(binder: Symbol) = new TypeTestCondStrategy {
type Result = Boolean
def typeTest(testedBinder: Symbol, expectedTp: Type): Result = testedBinder eq binder
def outerTest(testedBinder: Symbol, expectedTp: Type): Result = false
def nonNullTest(testedBinder: Symbol): Result = testedBinder eq binder
def equalsTest(pat: Tree, testedBinder: Symbol): Result = false // could in principle analyse pat and see if it's statically known to be non-null
def eqTest(pat: Tree, testedBinder: Symbol): Result = false // could in principle analyse pat and see if it's statically known to be non-null
def and(a: Result, b: Result): Result = a || b
def tru = false
}
}
/** implements the run-time aspects of (§8.2) (typedPattern has already done the necessary type transformations)
*
* Type patterns consist of types, type variables, and wildcards. A type pattern T is of one of the following forms:
- A reference to a class C, p.C, or T#C.
This type pattern matches any non-null instance of the given class.
Note that the prefix of the class, if it is given, is relevant for determining class instances.
For instance, the pattern p.C matches only instances of classes C which were created with the path p as prefix.
The bottom types scala.Nothing and scala.Null cannot be used as type patterns, because they would match nothing in any case.
- A singleton type p.type.
This type pattern matches only the value denoted by the path p
(that is, a pattern match involved a comparison of the matched value with p using method eq in class AnyRef). // TODO: the actual pattern matcher uses ==, so that's what I'm using for now
// https://issues.scala-lang.org/browse/SI-4577 "pattern matcher, still disappointing us at equality time"
- A compound type pattern T1 with ... with Tn where each Ti is a type pat- tern.
This type pattern matches all values that are matched by each of the type patterns Ti.
- A parameterized type pattern T[a1,...,an], where the ai are type variable patterns or wildcards _.
This type pattern matches all values which match T for some arbitrary instantiation of the type variables and wildcards.
The bounds or alias type of these type variable are determined as described in (§8.3).
- A parameterized type pattern scala.Array[T1], where T1 is a type pattern. // TODO
This type pattern matches any non-null instance of type scala.Array[U1], where U1 is a type matched by T1.
**/
case class TypeTestTreeMaker(prevBinder: Symbol, testedBinder: Symbol, expectedTp: Type, nextBinderTp: Type)(override val pos: Position, extractorArgTypeTest: Boolean = false) extends CondTreeMaker {
import TypeTestTreeMaker._
println("TTTM"+((prevBinder, extractorArgTypeTest, testedBinder, expectedTp, nextBinderTp)))
lazy val outerTestNeeded = (
(expectedTp.normalizedPrefix ne NoPrefix)
&& !expectedTp.normalizedPrefix.typeSymbol.isPackageObject
&& true //needsOuterTest(expectedTp, testedBinder.info, matchOwner) // todo
)
// the logic to generate the run-time test that follows from the fact that
// a `prevBinder` is expected to have type `expectedTp`
// the actual tree-generation logic is factored out, since the analyses generate Cond(ition)s rather than Trees
// TODO: `null match { x : T }` will yield a check that (indirectly) tests whether `null ne null`
// don't bother (so that we don't end up with the warning "comparing values of types Null and Null using `ne' will always yield false")
def renderCondition(cs: TypeTestCondStrategy): cs.Result = {
import cs._
// propagate expected type
def expTp(t: Tree): t.type = t // setType expectedTp todo:
def testedWide = testedBinder.info.widen
def expectedWide = expectedTp.widen
def isAnyRef = testedWide <:< ctx.definitions.AnyRefType
def isAsExpected = testedWide <:< expectedTp
def isExpectedPrimitiveType = isAsExpected && ctx.definitions.ScalaValueClasses.contains(expectedTp.classSymbol)
def isExpectedReferenceType = isAsExpected && (expectedTp <:< ctx.definitions.AnyRefType)
def mkNullTest = nonNullTest(testedBinder)
def mkOuterTest = outerTest(testedBinder, expectedTp)
def mkTypeTest = typeTest(testedBinder, expectedWide)
def mkEqualsTest(lhs: Tree): cs.Result = equalsTest(lhs, testedBinder)
def mkEqTest(lhs: Tree): cs.Result = eqTest(lhs, testedBinder)
def addOuterTest(res: cs.Result): cs.Result = if (outerTestNeeded) and(res, mkOuterTest) else res
// If we conform to expected primitive type:
// it cannot be null and cannot have an outer pointer. No further checking.
// If we conform to expected reference type:
// have to test outer and non-null
// If we do not conform to expected type:
// have to test type and outer (non-null is implied by successful type test)
def mkDefault = (
if (isExpectedPrimitiveType) tru
else addOuterTest(
if (isExpectedReferenceType) mkNullTest
else mkTypeTest
)
)
// true when called to type-test the argument to an extractor
// don't do any fancy equality checking, just test the type
// TODO: verify that we don't need to special-case Array
// I think it's okay:
// - the isInstanceOf test includes a test for the element type
// - Scala's arrays are invariant (so we don't drop type tests unsoundly)
if (extractorArgTypeTest) mkDefault
else expectedTp match {
case ThisType(sym) if sym.flags is Flags.Module => and(mkEqualsTest(ref(sym)), mkTypeTest) // must use == to support e.g. List() == Nil
case t:SingletonType => mkEqTest(singleton(expectedTp)) // SI-4577, SI-4897
case ConstantType(Constant(null)) if isAnyRef => mkEqTest(expTp(Literal(Constant(null))))
case ConstantType(const) => mkEqualsTest(expTp(Literal(const)))
case ThisType(sym) => mkEqTest(expTp(This(sym)))
case _ => mkDefault
}
}
val cond = renderCondition(treeCondStrategy)
val res = codegen._asInstanceOf(testedBinder, nextBinderTp)
// is this purely a type test, e.g. no outer check, no equality tests (used in switch emission)
def isPureTypeTest = renderCondition(pureTypeTestChecker)
def impliesBinderNonNull(binder: Symbol) = renderCondition(nonNullImpliedByTestChecker(binder))
override def toString = "TT"+((expectedTp, testedBinder.name, nextBinderTp))
}
// need to substitute to deal with existential types -- TODO: deal with existentials better, don't substitute (see RichClass during quick.comp)
case class EqualityTestTreeMaker(prevBinder: Symbol, patTree: Tree, override val pos: Position) extends CondTreeMaker {
val nextBinderTp = prevBinder.info.widen
// NOTE: generate `patTree == patBinder`, since the extractor must be in control of the equals method (also, patBinder may be null)
// equals need not be well-behaved, so don't intersect with pattern's (stabilized) type (unlike MaybeBoundTyped's accumType, where it's required)
val cond = codegen._equals(patTree, prevBinder)
val res = ref(prevBinder)
override def toString = "ET"+((prevBinder.name, patTree))
}
case class AlternativesTreeMaker(prevBinder: Symbol, var altss: List[List[TreeMaker]], pos: Position) extends TreeMaker with NoNewBinders {
// don't substitute prevBinder to nextBinder, a set of alternatives does not need to introduce a new binder, simply reuse the previous one
override private[TreeMakers] def incorporateOuterSubstitution(outerSubst: Substitution): Unit = {
super.incorporateOuterSubstitution(outerSubst)
altss = altss map (alts => propagateSubstitution(alts, substitution))
}
def chainBefore(next: Tree)(codegenAlt: Casegen): Tree = {
/*atPos(pos)*/{
// one alternative may still generate multiple trees (e.g., an extractor call + equality test)
// (for now,) alternatives may not bind variables (except wildcards), so we don't care about the final substitution built internally by makeTreeMakers
val combinedAlts = altss map (altTreeMakers =>
((casegen: Casegen) => combineExtractors(altTreeMakers :+ TrivialTreeMaker(casegen.one(Literal(Constant(true)))))(casegen))
)
val findAltMatcher = codegenAlt.matcher(EmptyTree, NoSymbol, ctx.definitions.BooleanType)(combinedAlts, Some(x => Literal(Constant(false))))
codegenAlt.ifThenElseZero(findAltMatcher, substitution(next))
}
}
}
case class GuardTreeMaker(guardTree: Tree) extends TreeMaker with NoNewBinders {
val pos = guardTree.pos
def chainBefore(next: Tree)(casegen: Casegen): Tree = casegen.flatMapGuard(substitution(guardTree), next)
override def toString = "G("+ guardTree +")"
}
// combineExtractors changes the current substitution's of the tree makers in `treeMakers`
// requires propagateSubstitution(treeMakers) has been called
def combineExtractors(treeMakers: List[TreeMaker])(casegen: Casegen): Tree =
treeMakers.foldRight(EmptyTree: Tree)((a, b) => a.chainBefore(b)(casegen))
def removeSubstOnly(makers: List[TreeMaker]) = makers filterNot (_.isInstanceOf[SubstOnlyTreeMaker])
// a foldLeft to accumulate the localSubstitution left-to-right
// it drops SubstOnly tree makers, since their only goal in life is to propagate substitutions to the next tree maker, which is fullfilled by propagateSubstitution
def propagateSubstitution(treeMakers: List[TreeMaker], initial: Substitution): List[TreeMaker] = {
var accumSubst: Substitution = initial
treeMakers foreach { maker =>
maker incorporateOuterSubstitution accumSubst
accumSubst = maker.substitution
}
removeSubstOnly(treeMakers)
}
// calls propagateSubstitution on the treemakers
def combineCases(scrut: Tree, scrutSym: Symbol, casesRaw: List[List[TreeMaker]], pt: Type, owner: Symbol, matchFailGenOverride: Option[Symbol => Tree]): Tree = {
// drops SubstOnlyTreeMakers, since their effect is now contained in the TreeMakers that follow them
val casesNoSubstOnly = casesRaw map (propagateSubstitution(_, EmptySubstitution))
combineCasesNoSubstOnly(scrut, scrutSym, casesNoSubstOnly, pt, owner, matchFailGenOverride)
}
// pt is the fully defined type of the cases (either pt or the lub of the types of the cases)
def combineCasesNoSubstOnly(scrut: Tree, scrutSym: Symbol, casesNoSubstOnly: List[List[TreeMaker]], pt: Type, owner: Symbol, matchFailGenOverride: Option[Symbol => Tree]): Tree =
/*fixerUpper(owner, scrut.pos)*/ {
def matchFailGen = matchFailGenOverride orElse Some((arg: Symbol) => Throw(New(defn.MatchErrorType, List(ref(arg)))))
println("combining cases: "+ (casesNoSubstOnly.map(_.mkString(" >> ")).mkString("{", "\n", "}")))
val (suppression, requireSwitch): (Suppression, Boolean) =
/*if (settings.XnoPatmatAnalysis)*/ (Suppression.NoSuppression, false)
/*else scrut match {
case Typed(tree, tpt) =>
val suppressExhaustive = tpt.tpe hasAnnotation UncheckedClass
val supressUnreachable = tree match {
case Ident(name) if name startsWith nme.CHECK_IF_REFUTABLE_STRING => true // SI-7183 don't warn for withFilter's that turn out to be irrefutable.
case _ => false
}
val suppression = Suppression(suppressExhaustive, supressUnreachable)
// matches with two or fewer cases need not apply for switchiness (if-then-else will do)
val requireSwitch = treeInfo.isSwitchAnnotation(tpt.tpe) && casesNoSubstOnly.lengthCompare(2) > 0
(suppression, requireSwitch)
case _ =>
(Suppression.NoSuppression, false)
}*/
emitSwitch(scrut, scrutSym, casesNoSubstOnly, pt, matchFailGenOverride, suppression.exhaustive).getOrElse{
if (requireSwitch) ctx.warning("could not emit switch for @switch annotated match", scrut.pos)
if (casesNoSubstOnly nonEmpty) {
// before optimizing, check casesNoSubstOnly for presence of a default case,
// since DCE will eliminate trivial cases like `case _ =>`, even if they're the last one
// exhaustivity and reachability must be checked before optimization as well
// TODO: improve notion of trivial/irrefutable -- a trivial type test before the body still makes for a default case
// ("trivial" depends on whether we're emitting a straight match or an exception, or more generally, any supertype of scrutSym.tpe is a no-op)
// irrefutability checking should use the approximation framework also used for CSE, unreachability and exhaustivity checking
val synthCatchAll: Option[Symbol => Tree] =
if (casesNoSubstOnly.nonEmpty && {
val nonTrivLast = casesNoSubstOnly.last
nonTrivLast.nonEmpty && nonTrivLast.head.isInstanceOf[BodyTreeMaker]
}) None
else matchFailGen
analyzeCases(scrutSym, casesNoSubstOnly, pt, suppression)
val (cases, toHoist) = optimizeCases(scrutSym, casesNoSubstOnly, pt)
val matchRes = codegen.matcher(scrut, scrutSym, pt)(cases map combineExtractors, synthCatchAll)
if (toHoist isEmpty) matchRes else Block(toHoist, matchRes)
} else {
codegen.matcher(scrut, scrutSym, pt)(Nil, matchFailGen)
}
}
}
// TODO: do this during tree construction, but that will require tracking the current owner in treemakers
// TODO: assign more fine-grained positions
// fixes symbol nesting, assigns positions
/*protected def fixerUpper(origOwner: Symbol, pos: Position) = new Traverser {
currentOwner = origOwner
override def traverse(t: Tree) {
t match {
case Function(_, _) if t.symbol == NoSymbol =>
t.symbol = currentOwner.newAnonymousFunctionValue(t.pos)
debug.patmat("new symbol for "+ ((t, t.symbol.ownerChain)))
case Function(_, _) if (t.symbol.owner == NoSymbol) || (t.symbol.owner == origOwner) =>
debug.patmat("fundef: "+ ((t, t.symbol.ownerChain, currentOwner.ownerChain)))
t.symbol.owner = currentOwner
case d : DefTree if (d.symbol != NoSymbol) && ((d.symbol.owner == NoSymbol) || (d.symbol.owner == origOwner)) => // don't indiscriminately change existing owners! (see e.g., pos/t3440, pos/t3534, pos/unapplyContexts2)
debug.patmat("def: "+ ((d, d.symbol.ownerChain, currentOwner.ownerChain)))
d.symbol.moduleClass andAlso (_.owner = currentOwner)
d.symbol.owner = currentOwner
// TODO DD:
// case _ if (t.symbol != NoSymbol) && (t.symbol ne null) =>
debug.patmat("untouched "+ ((t, t.getClass, t.symbol.ownerChain, currentOwner.ownerChain)))
case _ =>
}
super.traverse(t)
}
// override def apply
// debug.patmat("before fixerupper: "+ xTree)
// currentRun.trackerFactory.snapshot()
// debug.patmat("after fixerupper")
// currentRun.trackerFactory.snapshot()
}*/
}
trait MatchOptimizer extends OptimizedCodegen with TreeMakers
/*with SwitchEmission // todo: toBe ported
with CommonSubconditionElimination*/ {
override def optimizeCases(prevBinder: Symbol, cases: List[List[TreeMaker]], pt: Type): (List[List[TreeMaker]], List[Tree]) = {
// TODO: do CSE on result of doDCE(prevBinder, cases, pt)
val optCases = cases// todo: doCSE(prevBinder, cases, pt)
val toHoist = Nil/*(
for (treeMakers <- optCases)
yield treeMakers.collect{case tm: ReusedCondTreeMaker => tm.treesToHoist}
).flatten.flatten.toList*/
(optCases, toHoist)
}
}
trait MatchTranslator extends TreeMakers with ScalacPatternExpanders {
def isBackquoted(x: Ident) = x.isInstanceOf[BackquotedIdent]
def isVarPattern(pat: Tree): Boolean = pat match {
case x: Ident => !isBackquoted(x) && nme.isVariableName(x.name)
case _ => false
}
/** A conservative approximation of which patterns do not discern anything.
* They are discarded during the translation.
*/
object WildcardPattern {
def unapply(pat: Tree): Boolean = pat match {
case Bind(nme.WILDCARD, WildcardPattern()) => true // don't skip when binding an interesting symbol!
//case Star(WildcardPattern()) => true // dd todo:?
case x: Ident => isVarPattern(x)
case Alternative(ps) => ps forall unapply
case EmptyTree => true
case _ => false
}
}
object PatternBoundToUnderscore {
def unapply(pat: Tree): Boolean = pat match {
case Bind(nme.WILDCARD, _) => true // don't skip when binding an interesting symbol!
case Ident(nme.WILDCARD) => true
case Alternative(ps) => ps forall unapply
case Typed(PatternBoundToUnderscore(), _) => true
case _ => false
}
}
object SymbolBound {
def unapply(tree: Tree): Option[(Symbol, Tree)] = tree match {
case Bind(_, expr) if tree.symbol.exists => Some(tree.symbol -> expr)
case _ => None
}
}
// Always map repeated params to sequences
private def setVarInfo(sym: Symbol, info: Type) ={
//setInfo debug.patmatResult(s"changing ${sym.defString} to")(repeatedToSeq(info))
if(sym.info =:= info) assert(false, "should this happen?")
sym
}
def newBoundTree(tree: Tree, pt: Type): BoundTree = tree match {
case SymbolBound(sym, expr) => BoundTree(setVarInfo(sym, pt), expr)
case _ => BoundTree(setVarInfo(freshSym(tree.pos, prefix = "p"), pt), tree)
}
final case class BoundTree(binder: Symbol, tree: Tree) {
private lazy val extractor = ExtractorCall(tree)
def pos = tree.pos
def tpe = binder.info.dealias.widen // the type of the variable bound to the pattern
def pt = unbound match {
// case Star(tpt) => this glbWith seqType(tpt.tpe) dd todo:
case TypeBound(tpe) => tpe
case tree => tree.tpe
}
def glbWith(other: Type) = ctx.typeComparer.glb(tpe :: other :: Nil)// .normalize
object SymbolAndTypeBound {
def unapply(tree: Tree): Option[(Symbol, Type)] = tree match {
case SymbolBound(sym, TypeBound(tpe)) => Some(sym -> tpe)
case TypeBound(tpe) => Some(binder -> tpe)
case _ => None
}
}
object TypeBound {
def unapply(tree: Tree): Option[Type] = tree match {
case Typed(Ident(_), _) if tree.tpe != null => Some(tree.tpe)
case _ => None
}
}
private def rebindTo(pattern: Tree) = BoundTree(binder, pattern)
private def step(treeMakers: TreeMaker*)(subpatterns: BoundTree*): TranslationStep = TranslationStep(treeMakers.toList, subpatterns.toList)
private def bindingStep(sub: Symbol, subpattern: Tree) = step(SubstOnlyTreeMaker(sub, binder))(rebindTo(subpattern))
private def equalityTestStep() = step(EqualityTestTreeMaker(binder, tree, pos))()
private def typeTestStep(sub: Symbol, subPt: Type) = step(TypeTestTreeMaker(sub, binder, subPt, glbWith(subPt))(pos))()
private def alternativesStep(alts: List[Tree]) = step(AlternativesTreeMaker(binder, translatedAlts(alts), alts.head.pos))()
private def translatedAlts(alts: List[Tree]) = alts map (alt => rebindTo(alt).translate())
private def noStep() = step()()
private def unsupportedPatternMsg = sm"""
|unsupported pattern: ${tree.show} / $this (this is a scalac bug.)
|""".trim
// example check: List[Int] <:< ::[Int]
private def extractorStep(): TranslationStep = {
def paramType = extractor.aligner.wholeType
import extractor.treeMaker
// chain a type-testing extractor before the actual extractor call
// it tests the type, checks the outer pointer and casts to the expected type
// TODO: the outer check is mandated by the spec for case classes, but we do it for user-defined unapplies as well [SPEC]
// (the prefix of the argument passed to the unapply must equal the prefix of the type of the binder)
lazy val typeTest = TypeTestTreeMaker(binder, binder, paramType, paramType)(pos, extractorArgTypeTest = true)
// check whether typetest implies binder is not null,
// even though the eventual null check will be on typeTest.nextBinder
// it'll be equal to binder casted to paramType anyway (and the type test is on binder)
def extraction: TreeMaker = treeMaker(typeTest.nextBinder, typeTest impliesBinderNonNull binder, pos)
// paramType = the type expected by the unapply
// TODO: paramType may contain unbound type params (run/t2800, run/t3530)
val makers = (
// Statically conforms to paramType
if (this ensureConformsTo paramType) treeMaker(binder, false, pos) :: Nil
else typeTest :: extraction :: Nil
)
step(makers: _*)(extractor.subBoundTrees: _*)
}
// Summary of translation cases. I moved the excerpts from the specification further below so all
// the logic can be seen at once.
//
// [1] skip wildcard trees -- no point in checking them
// [2] extractor and constructor patterns
// [3] replace subpatBinder by patBinder, as if the Bind was not there.
// It must be patBinder, as subpatBinder has the wrong info: even if the bind assumes a better type,
// this is not guaranteed until we cast
// [4] typed patterns - a typed pattern never has any subtrees
// must treat Typed and Bind together -- we need to know the patBinder of the Bind pattern to get at the actual type
// [5] literal and stable id patterns
// [6] pattern alternatives
// [7] symbol-less bind patterns - this happens in certain ill-formed programs, there'll be an error later
// don't fail here though (or should we?)
def nextStep(): TranslationStep = tree match {
case WildcardPattern() => noStep()
case _: UnApply | _: Apply => extractorStep()
case SymbolAndTypeBound(sym, tpe) => typeTestStep(sym, tpe)
case TypeBound(tpe) => typeTestStep(binder, tpe)
case SymbolBound(sym, expr) => bindingStep(sym, expr)
case Literal(Constant(_)) | Ident(_) | Select(_, _) | This(_) => equalityTestStep()
case Alternative(alts) => alternativesStep(alts)
case _ => ctx.error(unsupportedPatternMsg, pos) ; noStep()
}
def translate(): List[TreeMaker] = nextStep() merge (_.translate())
private def setInfo(paramType: Type): Boolean = {
ctx.warning(s"resetting info of $this to $paramType")
setVarInfo(binder, paramType)
true
}
// If <:< but not =:=, no type test needed, but the tree maker relies on the binder having
// exactly paramType (and not just some type compatible with it.) SI-6624 shows this is necessary
// because apparently patBinder may have an unfortunate type (.decls don't have the case field
// accessors) TODO: get to the bottom of this -- I assume it happens when type checking
// infers a weird type for an unapply call. By going back to the parameterType for the
// extractor call we get a saner type, so let's just do that for now.
def ensureConformsTo(paramType: Type): Boolean = (
(tpe =:= paramType)
|| (tpe <:< paramType) && setInfo(paramType)
)
private def concreteType = tpe.bounds.hi
private def unbound = unbind(tree)
private def tpe_s = if (pt <:< concreteType) "" + pt else s"$pt (binder: $tpe)"
private def at_s = unbound match {
case WildcardPattern() => ""
case pat => s" @ $pat"
}
override def toString = s"${binder.name}: $tpe_s$at_s"
}
// a list of TreeMakers that encode `patTree`, and a list of arguments for recursive invocations of `translatePattern` to encode its subpatterns
final case class TranslationStep(makers: List[TreeMaker], subpatterns: List[BoundTree]) {
def merge(f: BoundTree => List[TreeMaker]): List[TreeMaker] = makers ::: (subpatterns flatMap f)
override def toString = if (subpatterns.isEmpty) "" else subpatterns.mkString("(", ", ", ")")
}
def isSyntheticDefaultCase(cdef: CaseDef) = cdef match {
case CaseDef(Bind(nme.DEFAULT_CASE, _), EmptyTree, _) => true
case _ => false
}
def elimAnonymousClass(t: Type) = t match {
case t:TypeRef if t.symbol.isAnonymousClass =>
t.symbol.asClass.typeRef.asSeenFrom(t.prefix, t.symbol.owner)
case _ =>
t
}
/** Is this pattern node a catch-all or type-test pattern? */
def isCatchCase(cdef: CaseDef) = cdef match {
case CaseDef(Typed(Ident(nme.WILDCARD), tpt), EmptyTree, _) =>
isSimpleThrowable(tpt.tpe)
case CaseDef(Bind(_, Typed(Ident(nme.WILDCARD), tpt)), EmptyTree, _) =>
isSimpleThrowable(tpt.tpe)
case _ =>
isDefaultCase(cdef)
}
def isNonBottomSubClass(thiz: Symbol, that: Symbol)(implicit ctx: Context): Boolean = (
(thiz eq that) || thiz.isError || that.isError ||
thiz.info.baseClasses.contains(that)
)
private def isSimpleThrowable(tp: Type)(implicit ctx: Context): Boolean = tp match {
case tp @ TypeRef(pre, _) =>
val sym = tp.symbol
(pre == NoPrefix || pre.widen.typeSymbol.isStatic) &&
(isNonBottomSubClass(sym, ctx.definitions.ThrowableClass)) && /* bq */ !(sym is Flags.Trait)
case _ =>
false
}
/** Implement a pattern match by turning its cases (including the implicit failure case)
* into the corresponding (monadic) extractors, and combining them with the `orElse` combinator.
*
* For `scrutinee match { case1 ... caseN }`, the resulting tree has the shape
* `runOrElse(scrutinee)(x => translateCase1(x).orElse(translateCase2(x)).....orElse(zero))`
*
* NOTE: the resulting tree is not type checked, nor are nested pattern matches transformed
* thus, you must typecheck the result (and that will in turn translate nested matches)
* this could probably optimized... (but note that the matchStrategy must be solved for each nested patternmatch)
*/
def translateMatch(match_ : Match): Tree = {
val Match(selector, cases) = match_
val (nonSyntheticCases, defaultOverride) = cases match {
case init :+ last if isSyntheticDefaultCase(last) => (init, Some(((scrut: Symbol) => last.body)))
case _ => (cases, None)
}
// checkMatchVariablePatterns(nonSyntheticCases) // only used for warnings
// we don't transform after uncurry
// (that would require more sophistication when generating trees,
// and the only place that emits Matches after typers is for exception handling anyway)
/*if (phase.id >= currentRun.uncurryPhase.id)
devWarning(s"running translateMatch past uncurry (at $phase) on $selector match $cases")*/
println("translating "+ cases.mkString("{", "\n", "}"))
//val start = if (Statistics.canEnable) Statistics.startTimer(patmatNanos) else null
val selectorTp = elimAnonymousClass(selector.tpe.widen/*withoutAnnotations*/)
// when one of the internal cps-type-state annotations is present, strip all CPS annotations
///val origPt = removeCPSFromPt(match_.tpe)
// relevant test cases: pos/existentials-harmful.scala, pos/gadt-gilles.scala, pos/t2683.scala, pos/virtpatmat_exist4.scala
// pt is the skolemized version
val pt = match_.tpe //repeatedToSeq(origPt)
// val packedPt = repeatedToSeq(typer.packedType(match_, context.owner))
val selectorSym = freshSym(selector.pos, pureType(selectorTp))
selectorSym.setFlag(Flags.SyntheticCase)
// pt = Any* occurs when compiling test/files/pos/annotDepMethType.scala with -Xexperimental
val combined = combineCases(selector, selectorSym, nonSyntheticCases map translateCase(selectorSym, pt), pt, matchOwner, defaultOverride)
// if (Statistics.canEnable) Statistics.stopTimer(patmatNanos, start)
combined
}
// return list of typed CaseDefs that are supported by the backend (typed/bind/wildcard)
// we don't have a global scrutinee -- the caught exception must be bound in each of the casedefs
// there's no need to check the scrutinee for null -- "throw null" becomes "throw new NullPointerException"
// try to simplify to a type-based switch, or fall back to a catch-all case that runs a normal pattern match
// unlike translateMatch, we type our result before returning it
def translateTry(caseDefs: List[CaseDef], pt: Type, pos: Position): List[CaseDef] =
// if they're already simple enough to be handled by the back-end, we're done
if (caseDefs forall treeInfo.isCatchCase) caseDefs
else {
val swatches = { // switch-catches
val bindersAndCases = caseDefs map { caseDef =>
// generate a fresh symbol for each case, hoping we'll end up emitting a type-switch (we don't have a global scrut there)
// if we fail to emit a fine-grained switch, have to do translateCase again with a single scrutSym (TODO: uniformize substitution on treemakers so we can avoid this)
val caseScrutSym = freshSym(pos, pureType(ThrowableTpe))
(caseScrutSym, propagateSubstitution(translateCase(caseScrutSym, pt)(caseDef), EmptySubstitution))
}
for(cases <- emitTypeSwitch(bindersAndCases, pt).toList
if cases forall treeInfo.isCatchCase; // must check again, since it's not guaranteed -- TODO: can we eliminate this? e.g., a type test could test for a trait or a non-trivial prefix, which are not handled by the back-end
cse <- cases) yield fixerUpper(matchOwner, pos)(cse).asInstanceOf[CaseDef]
}
val catches = if (swatches.nonEmpty) swatches else {
val scrutSym = freshSym(pos, pureType(ThrowableTpe))
val casesNoSubstOnly = caseDefs map { caseDef => (propagateSubstitution(translateCase(scrutSym, pt)(caseDef), EmptySubstitution))}
val exSym = freshSym(pos, pureType(ThrowableTpe), "ex")
List(
atPos(pos) {
CaseDef(
Bind(exSym, Ident(nme.WILDCARD)), // TODO: does this need fixing upping?
EmptyTree,
combineCasesNoSubstOnly(REF(exSym), scrutSym, casesNoSubstOnly, pt, matchOwner, Some(scrut => Throw(REF(exSym))))
)
})
}
typer.typedCases(catches, ThrowableTpe, WildcardType)
}
/** The translation of `pat if guard => body` has two aspects:
* 1) the substitution due to the variables bound by patterns
* 2) the combination of the extractor calls using `flatMap`.
*
* 2) is easy -- it looks like: `translatePattern_1.flatMap(translatePattern_2....flatMap(translatePattern_N.flatMap(translateGuard.flatMap((x_i) => success(Xbody(x_i)))))...)`
* this must be right-leaning tree, as can be seen intuitively by considering the scope of bound variables:
* variables bound by pat_1 must be visible from the function inside the left-most flatMap right up to Xbody all the way on the right
* 1) is tricky because translatePattern_i determines the shape of translatePattern_i+1:
* zoom in on `translatePattern_1.flatMap(translatePattern_2)` for example -- it actually looks more like:
* `translatePattern_1(x_scrut).flatMap((x_1) => {y_i -> x_1._i}translatePattern_2)`
*
* `x_1` references the result (inside the monad) of the extractor corresponding to `pat_1`,
* this result holds the values for the constructor arguments, which translatePattern_1 has extracted
* from the object pointed to by `x_scrut`. The `y_i` are the symbols bound by `pat_1` (in order)
* in the scope of the remainder of the pattern, and they must thus be replaced by:
* - (for 1-ary unapply) x_1
* - (for n-ary unapply, n > 1) selection of the i'th tuple component of `x_1`
* - (for unapplySeq) x_1.apply(i)
*
* in the treemakers,
*
* Thus, the result type of `translatePattern_i`'s extractor must conform to `M[(T_1,..., T_n)]`.
*
* Operationally, phase 1) is a foldLeft, since we must consider the depth-first-flattening of
* the transformed patterns from left to right. For every pattern ast node, it produces a transformed ast and
* a function that will take care of binding and substitution of the next ast (to the right).
*
*/
def translateCase(scrutSym: Symbol, pt: Type)(caseDef: CaseDef) = {
val CaseDef(pattern, guard, body) = caseDef
translatePattern(BoundTree(scrutSym, pattern)) ++ translateGuard(guard) :+ translateBody(body, pt)
}
def translatePattern(bound: BoundTree): List[TreeMaker] = bound.translate()
def translateGuard(guard: Tree): List[TreeMaker] =
if (guard == EmptyTree) Nil
else List(GuardTreeMaker(guard))
// TODO: 1) if we want to support a generalisation of Kotlin's patmat continue, must not hard-wire lifting into the monad (which is now done by codegen.one),
// so that user can generate failure when needed -- use implicit conversion to lift into monad on-demand?
// to enable this, probably need to move away from Option to a monad specific to pattern-match,
// so that we can return Option's from a match without ambiguity whether this indicates failure in the monad, or just some result in the monad
// 2) body.tpe is the type of the body after applying the substitution that represents the solution of GADT type inference
// need the explicit cast in case our substitutions in the body change the type to something that doesn't take GADT typing into account
def translateBody(body: Tree, matchPt: Type): TreeMaker =
BodyTreeMaker(body, matchPt)
// Some notes from the specification
/*A constructor pattern is of the form c(p1, ..., pn) where n ≥ 0.
It consists of a stable identifier c, followed by element patterns p1, ..., pn.
The constructor c is a simple or qualified name which denotes a case class (§5.3.2).
If the case class is monomorphic, then it must conform to the expected type of the pattern,
and the formal parameter types of x’s primary constructor (§5.3) are taken as the expected
types of the element patterns p1, ..., pn.
If the case class is polymorphic, then its type parameters are instantiated so that the
instantiation of c conforms to the expected type of the pattern.
The instantiated formal parameter types of c’s primary constructor are then taken as the
expected types of the component patterns p1, ..., pn.
The pattern matches all objects created from constructor invocations c(v1, ..., vn)
where each element pattern pi matches the corresponding value vi .
A special case arises when c’s formal parameter types end in a repeated parameter.
This is further discussed in (§8.1.9).
**/
/* A typed pattern x : T consists of a pattern variable x and a type pattern T.
The type of x is the type pattern T, where each type variable and wildcard is replaced by a fresh, unknown type.
This pattern matches any value matched by the type pattern T (§8.2); it binds the variable name to that value.
*/
/* A pattern binder x@p consists of a pattern variable x and a pattern p.
The type of the variable x is the static type T of the pattern p.
This pattern matches any value v matched by the pattern p,
provided the run-time type of v is also an instance of T, <-- TODO! https://issues.scala-lang.org/browse/SI-1503
and it binds the variable name to that value.
*/
/* 8.1.4 Literal Patterns
A literal pattern L matches any value that is equal (in terms of ==) to the literal L.
The type of L must conform to the expected type of the pattern.
8.1.5 Stable Identifier Patterns (a stable identifier r (see §3.1))
The pattern matches any value v such that r == v (§12.1).
The type of r must conform to the expected type of the pattern.
*/
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// helper methods: they analyze types and trees in isolation, but they are not (directly) concerned with the structure of the overall translation
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
object ExtractorCall {
// TODO: check unargs == args
def apply(tree: Tree): ExtractorCall = tree match {
case UnApply(unfun, args) => new ExtractorCallRegular(alignPatterns(tree), unfun, args) // extractor
case Apply(fun, args) => new ExtractorCallProd(alignPatterns(tree), fun, args) // case class
}
}
abstract class ExtractorCall(val aligner: PatternAligned) {
import aligner._
def fun: Tree
def args: List[Tree]
// don't go looking for selectors if we only expect one pattern
def rawSubPatTypes = aligner.extractedTypes
def resultInMonad = if (isBool) UnitTpe else typeOfMemberNamedGet(resultType)
def resultType = fun.tpe.finalResultType
/** Create the TreeMaker that embodies this extractor call
*
* `binder` has been casted to `paramType` if necessary
* `binderKnownNonNull` indicates whether the cast implies `binder` cannot be null
* when `binderKnownNonNull` is `true`, `ProductExtractorTreeMaker` does not do a (redundant) null check on binder
*/
def treeMaker(binder: Symbol, binderKnownNonNull: Boolean, pos: Position): TreeMaker
// `subPatBinders` are the variables bound by this pattern in the following patterns
// subPatBinders are replaced by references to the relevant part of the extractor's result (tuple component, seq element, the result as-is)
// must set infos to `subPatTypes`, which are provided by extractor's result,
// as b.info may be based on a Typed type ascription, which has not been taken into account yet by the translation
// (it will later result in a type test when `tp` is not a subtype of `b.info`)
// TODO: can we simplify this, together with the Bound case?
def subPatBinders = subBoundTrees map (_.binder)
lazy val subBoundTrees = (args, subPatTypes).zipped map newBoundTree
// never store these in local variables (for PreserveSubPatBinders)
lazy val ignoredSubPatBinders: Set[Symbol] = subPatBinders zip args collect { case (b, PatternBoundToUnderscore()) => b } toSet
// do repeated-parameter expansion to match up with the expected number of arguments (in casu, subpatterns)
private def nonStarSubPatTypes = aligner.typedNonStarPatterns map (_.tpe)
def subPatTypes: List[Type] = typedPatterns map (_.tpe)
// there are `productArity` non-seq elements in the tuple.
protected def firstIndexingBinder = productArity
protected def expectedLength = elementArity
protected def lastIndexingBinder = totalArity - starArity - 1
private def productElemsToN(binder: Symbol, n: Int): List[Tree] = 1 to n map tupleSel(binder) toList
private def genTake(binder: Symbol, n: Int): List[Tree] = (0 until n).toList map (codegen index seqTree(binder))
private def genDrop(binder: Symbol, n: Int): List[Tree] = codegen.drop(seqTree(binder))(expectedLength) :: Nil
// codegen.drop(seqTree(binder))(nbIndexingIndices)))).toList
protected def seqTree(binder: Symbol) = tupleSel(binder)(firstIndexingBinder + 1)
protected def tupleSel(binder: Symbol)(i: Int): Tree = codegen.tupleSel(binder)(i)
// the trees that select the subpatterns on the extractor's result,
// referenced by `binder`
protected def subPatRefsSeq(binder: Symbol): List[Tree] = {
def lastTrees: List[Tree] = (
if (!aligner.isStar) Nil
else if (expectedLength == 0) seqTree(binder) :: Nil
else genDrop(binder, expectedLength)
)
// this error-condition has already been checked by checkStarPatOK:
// if(isSeq) assert(firstIndexingBinder + nbIndexingIndices + (if(lastIsStar) 1 else 0) == totalArity, "(resultInMonad, ts, subPatTypes, subPats)= "+(resultInMonad, ts, subPatTypes, subPats))
// [1] there are `firstIndexingBinder` non-seq tuple elements preceding the Seq
// [2] then we have to index the binder that represents the sequence for the remaining subpatterns, except for...
// [3] the last one -- if the last subpattern is a sequence wildcard:
// drop the prefix (indexed by the refs on the preceding line), return the remainder
( productElemsToN(binder, firstIndexingBinder)
++ genTake(binder, expectedLength)
++ lastTrees
).toList
}
// the trees that select the subpatterns on the extractor's result, referenced by `binder`
// require (nbSubPats > 0 && (!lastIsStar || isSeq))
protected def subPatRefs(binder: Symbol): List[Tree] = (
if (totalArity > 0 && isSeq) subPatRefsSeq(binder)
else productElemsToN(binder, totalArity)
)
private def compareInts(t1: Tree, t2: Tree) =
gen.mkMethodCall(termMember(ScalaPackage, "math"), TermName("signum"), Nil, (t1 INT_- t2) :: Nil)
protected def lengthGuard(binder: Symbol): Option[Tree] =
// no need to check unless it's an unapplySeq and the minimal length is non-trivially satisfied
checkedLength map { expectedLength =>
// `binder.lengthCompare(expectedLength)`
// ...if binder has a lengthCompare method, otherwise
// `scala.math.signum(binder.length - expectedLength)`
def checkExpectedLength = sequenceType member nme.lengthCompare match {
case NoSymbol => compareInts(Select(seqTree(binder), nme.length), LIT(expectedLength))
case lencmp => (seqTree(binder) DOT lencmp)(LIT(expectedLength))
}
// the comparison to perform
// when the last subpattern is a wildcard-star the expectedLength is but a lower bound
// (otherwise equality is required)
def compareOp: (Tree, Tree) => Tree =
if (aligner.isStar) _ INT_>= _
else _ INT_== _
// `if (binder != null && $checkExpectedLength [== | >=] 0) then else zero`
(seqTree(binder) ANY_!= NULL) AND compareOp(checkExpectedLength, ZERO)
}
def checkedLength: Option[Int] =
// no need to check unless it's an unapplySeq and the minimal length is non-trivially satisfied
if (!isSeq || expectedLength < starArity) None
else Some(expectedLength)
}
// TODO: to be called when there's a def unapplyProd(x: T): U
// U must have N members _1,..., _N -- the _i are type checked, call their type Ti,
// for now only used for case classes -- pretending there's an unapplyProd that's the identity (and don't call it)
class ExtractorCallProd(aligner: PatternAligned, val fun: Tree, val args: List[Tree]) extends ExtractorCall(aligner) {
/** Create the TreeMaker that embodies this extractor call
*
* `binder` has been casted to `paramType` if necessary
* `binderKnownNonNull` indicates whether the cast implies `binder` cannot be null
* when `binderKnownNonNull` is `true`, `ProductExtractorTreeMaker` does not do a (redundant) null check on binder
*/
def treeMaker(binder: Symbol, binderKnownNonNull: Boolean, pos: Position): TreeMaker = {
val paramAccessors = binder.constrParamAccessors
// binders corresponding to mutable fields should be stored (SI-5158, SI-6070)
// make an exception for classes under the scala package as they should be well-behaved,
// to optimize matching on List
val mutableBinders = (
if (!binder.info.typeSymbol.hasTransOwner(ScalaPackageClass) &&
(paramAccessors exists (_.isMutable)))
subPatBinders.zipWithIndex.collect{ case (binder, idx) if paramAccessors(idx).isMutable => binder }
else Nil
)
// checks binder ne null before chaining to the next extractor
ProductExtractorTreeMaker(binder, lengthGuard(binder))(subPatBinders, subPatRefs(binder), mutableBinders, binderKnownNonNull, ignoredSubPatBinders)
}
// reference the (i-1)th case accessor if it exists, otherwise the (i-1)th tuple component
override protected def tupleSel(binder: Symbol)(i: Int): Tree = {
val accessors = binder.caseFieldAccessors
if (accessors isDefinedAt (i-1)) REF(binder) DOT accessors(i-1)
else codegen.tupleSel(binder)(i) // this won't type check for case classes, as they do not inherit ProductN
}
}
class ExtractorCallRegular(aligner: PatternAligned, extractorCallIncludingDummy: Tree, val args: List[Tree]) extends ExtractorCall(aligner) {
val Unapplied(fun) = extractorCallIncludingDummy
/** Create the TreeMaker that embodies this extractor call
*
* `binder` has been casted to `paramType` if necessary
* `binderKnownNonNull` is not used in this subclass
*
* TODO: implement review feedback by @retronym:
* Passing the pair of values around suggests:
* case class Binder(sym: Symbol, knownNotNull: Boolean).
* Perhaps it hasn't reached critical mass, but it would already clean things up a touch.
*/
def treeMaker(patBinderOrCasted: Symbol, binderKnownNonNull: Boolean, pos: Position): TreeMaker = {
// the extractor call (applied to the binder bound by the flatMap corresponding
// to the previous (i.e., enclosing/outer) pattern)
val extractorApply = atPos(pos)(spliceApply(patBinderOrCasted))
// can't simplify this when subPatBinders.isEmpty, since UnitTpe is definitely
// wrong when isSeq, and resultInMonad should always be correct since it comes
// directly from the extractor's result type
val binder = freshSym(pos, pureType(resultInMonad))
ExtractorTreeMaker(extractorApply, lengthGuard(binder), binder)(
subPatBinders,
subPatRefs(binder),
aligner.isBool,
checkedLength,
patBinderOrCasted,
ignoredSubPatBinders
)
}
override protected def seqTree(binder: Symbol): Tree =
if (firstIndexingBinder == 0) REF(binder)
else super.seqTree(binder)
// the trees that select the subpatterns on the extractor's result, referenced by `binder`
// require (totalArity > 0 && (!lastIsStar || isSeq))
override protected def subPatRefs(binder: Symbol): List[Tree] =
if (aligner.isSingle) ref(binder) :: Nil // special case for extractors
else super.subPatRefs(binder)
protected def spliceApply(binder: Symbol): Tree = {
object splice extends Transformer {
def binderRef(pos: Position): Tree =
ref(binder) //setPos pos
override def transform(t: Tree) = t match {
// duplicated with the extractor Unapplied
case Apply(x, List(i @ Ident(nme.SELECTOR_DUMMY))) =>
cpy.Apply(t, x, binderRef(i.pos) :: Nil)
// SI-7868 Account for numeric widening, e.g. <unappplySelector>.toInt
case Apply(x, List(i @ (sel @ Select(Ident(nme.SELECTOR_DUMMY), name)))) =>
cpy.Apply(t, x, cpy.Select(sel, binderRef(i.pos), name) :: Nil)
case _ =>
super.transform(t)
}
}
splice transform extractorCallIncludingDummy
}
override def rawSubPatTypes = aligner.extractor.varargsTypes
}
}
/** An extractor returns: F1, F2, ..., Fi, opt[Seq[E] or E*]
* A case matches: P1, P2, ..., Pj, opt[Seq[E]]
* Put together: P1/F1, P2/F2, ... Pi/Fi, Pi+1/E, Pi+2/E, ... Pj/E, opt[Seq[E]]
*
* Here Pm/Fi is the last pattern to match the fixed arity section.
*
* productArity: the value of i, i.e. the number of non-sequence types in the extractor
* nonStarArity: the value of j, i.e. the number of non-star patterns in the case definition
* elementArity: j - i, i.e. the number of non-star patterns which must match sequence elements
* starArity: 1 or 0 based on whether there is a star (sequence-absorbing) pattern
* totalArity: nonStarArity + starArity, i.e. the number of patterns in the case definition
*
* Note that productArity is a function only of the extractor, and
* nonStar/star/totalArity are all functions of the patterns. The key
* value for aligning and typing the patterns is elementArity, as it
* is derived from both sets of information.
*/
trait PatternExpander[Pattern, Type] {
/** You'll note we're not inside the cake. "Pattern" and "Type" are
* arbitrary types here, and NoPattern and NoType arbitrary values.
*/
def NoPattern: Pattern
def NoType: Type
/** It's not optimal that we're carrying both sequence and repeated
* type here, but the implementation requires more unraveling before
* it can be avoided.
*
* sequenceType is Seq[T], elementType is T, repeatedType is T*.
*/
sealed case class Repeated(sequenceType: Type, elementType: Type, repeatedType: Type) {
def exists = elementType != NoType
def elementList = if (exists) elementType :: Nil else Nil
def sequenceList = if (exists) sequenceType :: Nil else Nil
def repeatedList = if (exists) repeatedType :: Nil else Nil
override def toString = s"${elementType}*"
}
object NoRepeated extends Repeated(NoType, NoType, NoType) {
override def toString = "<none>"
}
final case class Patterns(fixed: List[Pattern], star: Pattern) {
def hasStar = star != NoPattern
def starArity = if (hasStar) 1 else 0
def nonStarArity = fixed.length
def totalArity = nonStarArity + starArity
def starPatterns = if (hasStar) star :: Nil else Nil
def all = fixed ::: starPatterns
override def toString = all mkString ", "
}
/** An 'extractor' can be a case class or an unapply or unapplySeq method.
* Decoding what it is that they extract takes place before we arrive here,
* so that this class can concentrate only on the relationship between
* patterns and types.
*
* In a case class, the class is the unextracted type and the fixed and
* repeated types are derived from its constructor parameters.
*
* In an unapply, this is reversed: the parameter to the unapply is the
* unextracted type, and the other types are derived based on the return
* type of the unapply method.
*
* In other words, this case class and unapply are encoded the same:
*
* case class Foo(x: Int, y: Int, zs: Char*)
* def unapplySeq(x: Foo): Option[(Int, Int, Seq[Char])]
*
* Both are Extractor(Foo, Int :: Int :: Nil, Repeated(Seq[Char], Char, Char*))
*
* @param whole The type in its unextracted form
* @param fixed The non-sequence types which are extracted
* @param repeated The sequence type which is extracted
*/
final case class Extractor(whole: Type, fixed: List[Type], repeated: Repeated) {
require(whole != NoType, s"expandTypes($whole, $fixed, $repeated)")
def productArity = fixed.length
def hasSeq = repeated.exists
def elementType = repeated.elementType
def sequenceType = repeated.sequenceType
def allTypes = fixed ::: repeated.sequenceList
def varargsTypes = fixed ::: repeated.repeatedList
def isErroneous = allTypes contains NoType
private def typeStrings = fixed.map("" + _) ::: ( if (hasSeq) List("" + repeated) else Nil )
def offeringString = if (isErroneous) "<error>" else typeStrings match {
case Nil => "Boolean"
case tp :: Nil => tp
case tps => tps.mkString("(", ", ", ")")
}
override def toString = "%s => %s".format(whole, offeringString)
}
final case class TypedPat(pat: Pattern, tpe: Type) {
override def toString = s"$pat: $tpe"
}
/** If elementArity is...
* 0: A perfect match between extractor and the fixed patterns.
* If there is a star pattern it will match any sequence.
* > 0: There are more patterns than products. There will have to be a
* sequence which can populate at least <elementArity> patterns.
* < 0: There are more products than patterns: compile time error.
*/
final case class Aligned(patterns: Patterns, extractor: Extractor) {
def elementArity = patterns.nonStarArity - productArity
def productArity = extractor.productArity
def starArity = patterns.starArity
def totalArity = patterns.totalArity
def wholeType = extractor.whole
def sequenceType = extractor.sequenceType
def productTypes = extractor.fixed
def extractedTypes = extractor.allTypes
def typedNonStarPatterns = products ::: elements
def typedPatterns = typedNonStarPatterns ::: stars
def isBool = !isSeq && productArity == 0
def isSingle = !isSeq && totalArity == 1
def isStar = patterns.hasStar
def isSeq = extractor.hasSeq
private def typedAsElement(pat: Pattern) = TypedPat(pat, extractor.elementType)
private def typedAsSequence(pat: Pattern) = TypedPat(pat, extractor.sequenceType)
private def productPats = patterns.fixed take productArity
private def elementPats = patterns.fixed drop productArity
private def products = (productPats, productTypes).zipped map TypedPat
private def elements = elementPats map typedAsElement
private def stars = patterns.starPatterns map typedAsSequence
override def toString = s"""
|Aligned {
| patterns $patterns
| extractor $extractor
| arities $productArity/$elementArity/$starArity // product/element/star
| typed ${typedPatterns mkString ", "}
|}""".stripMargin.trim
}
}
/** This is scalac-specific logic layered on top of the scalac-agnostic
* "matching products to patterns" logic defined in PatternExpander.
*/
trait ScalacPatternExpanders {
type PatternAligned = ScalacPatternExpander#Aligned
implicit class AlignedOps(val aligned: PatternAligned) {
import aligned._
def expectedTypes = typedPatterns map (_.tpe)
def unexpandedFormals = extractor.varargsTypes
}
trait ScalacPatternExpander extends PatternExpander[Tree, Type] {
def NoPattern = EmptyTree
def NoType = NoType
def newPatterns(patterns: List[Tree]): Patterns = patterns match {
case init :+ last if isStar(last) => Patterns(init, last)
case _ => Patterns(patterns, NoPattern)
}
def elementTypeOf(tpe: Type) = {
val seq = repeatedToSeq(tpe)
( typeOfMemberNamedHead(seq)
orElse typeOfMemberNamedApply(seq)
orElse definitions.elementType(ArrayClass, seq)
)
}
def newExtractor(whole: Type, fixed: List[Type], repeated: Repeated): Extractor =
logResult(s"newExtractor($whole, $fixed, $repeated")(Extractor(whole, fixed, repeated))
// Turn Seq[A] into Repeated(Seq[A], A, A*)
def repeatedFromSeq(seqType: Type): Repeated = {
val elem = elementTypeOf(seqType)
val repeated = scalaRepeatedType(elem)
Repeated(seqType, elem, repeated)
}
// Turn A* into Repeated(Seq[A], A, A*)
def repeatedFromVarargs(repeated: Type): Repeated =
Repeated(repeatedToSeq(repeated), repeatedToSingle(repeated), repeated)
/** In this case we are basing the pattern expansion on a case class constructor.
* The argument is the MethodType carried by the primary constructor.
*/
def applyMethodTypes(method: Type): Extractor = {
val whole = method.finalResultType
method.paramTypes match {
case init :+ last if isScalaRepeatedParamType(last) => newExtractor(whole, init, repeatedFromVarargs(last))
case tps => newExtractor(whole, tps, NoRepeated)
}
}
/** In this case, expansion is based on an unapply or unapplySeq method.
* Unfortunately the MethodType does not carry the information of whether
* it was unapplySeq, so we have to funnel that information in separately.
*/
def unapplyMethodTypes(method: Type, isSeq: Boolean): Extractor = {
val whole = firstParamType(method)
val result = method.finalResultType
val expanded = (
if (result =:= BooleanTpe) Nil
else typeOfMemberNamedGet(result) match {
case rawGet if !hasSelectors(rawGet) => rawGet :: Nil
case rawGet => typesOfSelectors(rawGet)
}
)
expanded match {
case init :+ last if isSeq => newExtractor(whole, init, repeatedFromSeq(last))
case tps => newExtractor(whole, tps, NoRepeated)
}
}
}
object alignPatterns extends ScalacPatternExpander {
/** Converts a T => (A, B, C) extractor to a T => ((A, B, CC)) extractor.
*/
def tupleExtractor(extractor: Extractor): Extractor =
extractor.copy(fixed = tupleType(extractor.fixed) :: Nil)
private def validateAligned(tree: Tree, aligned: Aligned): Aligned = {
import aligned._
def owner = tree.symbol.owner
def offering = extractor.offeringString
def symString = tree.symbol.fullLocationString
def offerString = if (extractor.isErroneous) "" else s" offering $offering"
def arityExpected = ( if (extractor.hasSeq) "at least " else "" ) + productArity
def err(msg: String) = currentUnit.error(tree.pos, msg)
def warn(msg: String) = currentUnit.warning(tree.pos, msg)
def arityError(what: String) = err(s"$what patterns for $owner$offerString: expected $arityExpected, found $totalArity")
if (isStar && !isSeq)
err("Star pattern must correspond with varargs or unapplySeq")
else if (elementArity < 0)
arityError("not enough")
else if (elementArity > 0 && !extractor.hasSeq)
arityError("too many")
aligned
}
def apply(sel: Tree, args: List[Tree]): Aligned = {
val fn = sel match {
case Unapplied(fn) => fn
case _ => sel
}
val patterns = newPatterns(args)
val isSeq = sel.symbol.name == nme.unapplySeq
val isUnapply = sel.symbol.name == nme.unapply
val extractor = sel.symbol.name match {
case nme.unapply => unapplyMethodTypes(fn.tpe, isSeq = false)
case nme.unapplySeq => unapplyMethodTypes(fn.tpe, isSeq = true)
case _ => applyMethodTypes(fn.tpe)
}
/** Rather than let the error that is SI-6675 pollute the entire matching
* process, we will tuple the extractor before creation Aligned so that
* it contains known good values.
*/
def productArity = extractor.productArity
def acceptMessage = if (extractor.isErroneous) "" else s" to hold ${extractor.offeringString}"
val requiresTupling = isUnapply && patterns.totalArity == 1 && productArity > 1
if (requiresTupling && effectivePatternArity(args) == 1)
currentUnit.deprecationWarning(sel.pos, s"${sel.symbol.owner} expects $productArity patterns$acceptMessage but crushing into $productArity-tuple to fit single pattern (SI-6675)")
val normalizedExtractor = if (requiresTupling) tupleExtractor(extractor) else extractor
validateAligned(fn, Aligned(patterns, normalizedExtractor))
}
def apply(tree: Tree): Aligned = tree match {
case Apply(fn, args) => apply(fn, args)
case UnApply(fn, args) => apply(fn, args)
}
}
}
}
