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package dotty.tools.dotc
package core
import annotation.tailrec
import Symbols._
import Contexts._, Names._, Phases._, printing.Texts._, printing.Printer
import util.Positions.Position, util.SourcePosition
import collection.mutable.ListBuffer
import scala.language.implicitConversions
/** This object provides useful implicit decorators for types defined elsewhere */
object Decorators {
/** Turns Strings into PreNames, adding toType/TermName methods */
implicit class StringDecorator(val s: String) extends AnyVal with PreName {
def toTypeName: TypeName = typeName(s)
def toTermName: TermName = termName(s)
def toText(printer: Printer): Text = Str(s)
}
/** Implements a findSymbol method on iterators of Symbols that
* works like find but avoids Option, replacing None with NoSymbol.
*/
implicit class SymbolIteratorDecorator(val it: Iterator[Symbol]) extends AnyVal {
final def findSymbol(p: Symbol => Boolean): Symbol = {
while (it.hasNext) {
val sym = it.next
if (p(sym)) return sym
}
NoSymbol
}
}
final val MaxFilterRecursions = 1000
/** Implements filterConserve, zipWithConserve methods
* on lists that avoid dupliation of list nodes where feasible.
*/
implicit class ListDecorator[T](val xs: List[T]) extends AnyVal {
@inline final def mapconserve[U](f: T => U): List[U] = {
@tailrec
def loop(mapped: ListBuffer[U], unchanged: List[U], pending: List[T]): List[U] =
if (pending.isEmpty) {
if (mapped eq null) unchanged
else mapped.prependToList(unchanged)
} else {
val head0 = pending.head
val head1 = f(head0)
if (head1.asInstanceOf[AnyRef] eq head0.asInstanceOf[AnyRef])
loop(mapped, unchanged, pending.tail)
else {
val b = if (mapped eq null) new ListBuffer[U] else mapped
var xc = unchanged
while (xc ne pending) {
b += xc.head
xc = xc.tail
}
b += head1
val tail0 = pending.tail
loop(b, tail0.asInstanceOf[List[U]], tail0)
}
}
loop(null, xs.asInstanceOf[List[U]], xs)
}
/** Like `xs filter p` but returns list `xs` itself - instead of a copy -
* if `p` is true for all elements and `xs` is not longer
* than `MaxFilterRecursions`.
*/
def filterConserve(p: T => Boolean): List[T] = {
def loop(xs: List[T], nrec: Int): List[T] = xs match {
case Nil => xs
case x :: xs1 =>
if (nrec < MaxFilterRecursions) {
val ys1 = loop(xs1, nrec + 1)
if (p(x))
if (ys1 eq xs1) xs else x :: ys1
else
ys1
} else xs filter p
}
loop(xs, 0)
}
/** Like `(xs, ys).zipped.map(f)`, but returns list `xs` itself
* - instead of a copy - if function `f` maps all elements of
* `xs` to themselves. Also, it is required that `ys` is at least
* as long as `xs`.
*/
def zipWithConserve[U](ys: List[U])(f: (T, U) => T): List[T] =
if (xs.isEmpty) xs
else {
val x1 = f(xs.head, ys.head)
val xs1 = xs.tail.zipWithConserve(ys.tail)(f)
if ((x1.asInstanceOf[AnyRef] eq xs.head.asInstanceOf[AnyRef]) &&
(xs1 eq xs.tail)) xs
else x1 :: xs1
}
final def hasSameLengthAs[U](ys: List[U]): Boolean = {
@tailrec def loop(xs: List[T], ys: List[U]): Boolean =
if (xs.isEmpty) ys.isEmpty
else ys.nonEmpty && loop(xs.tail, ys.tail)
loop(xs, ys)
}
}
implicit class ListOfListDecorator[T](val xss: List[List[T]]) extends AnyVal {
def nestedMap[U](f: T => U): List[List[U]] = xss map (_ map f)
}
implicit class TextToString(val text: Text) extends AnyVal {
def show(implicit ctx: Context) = text.mkString(ctx.settings.pageWidth.value)
}
/** Implements a test whether a list of strings representing phases contains
* a given phase. The test returns true if the given phase starts with
* one of the names in the list of strings.
*/
implicit class PhaseListDecorator(val names: List[String]) extends AnyVal {
def containsPhase(phase: Phase) =
names exists (phase.name.startsWith)
}
implicit def sourcePos(pos: Position)(implicit ctx: Context): SourcePosition =
ctx.source.atPos(pos)
}
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