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Fix NPE in Implicits #1903

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Merged
merged 1 commit into from
Jan 16, 2017
Merged

Fix NPE in Implicits #1903

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14 changes: 11 additions & 3 deletions compiler/src/dotty/tools/dotc/typer/Implicits.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -155,14 +155,22 @@ object Implicits {
(ctx.scope eq outerImplicits.ctx.scope)) outerImplicits.level
else outerImplicits.level + 1

/** Is this the outermost implicits? This is the case if it either the implicits
* of NoContext, or the last one before it.
*/
private def isOuterMost = {
val finalImplicits = NoContext.implicits
(this eq finalImplicits) || (outerImplicits eq finalImplicits)
}

/** The implicit references that are eligible for type `tp`. */
def eligible(tp: Type): List[Candidate] = /*>|>*/ track(s"eligible in ctx") /*<|<*/ {
if (tp.hash == NotCached) computeEligible(tp)
else eligibleCache get tp match {
case Some(eligibles) =>
def elided(ci: ContextualImplicits): Int = {
val n = ci.refs.length
if (ci.outerImplicits == NoContext.implicits) n
if (ci.isOuterMost) n
else n + elided(ci.outerImplicits)
}
if (monitored) record(s"elided eligible refs", elided(this))
Expand All @@ -183,7 +191,7 @@ object Implicits {
private def computeEligible(tp: Type): List[Candidate] = /*>|>*/ ctx.traceIndented(i"computeEligible $tp in $refs%, %", implicitsDetailed) /*<|<*/ {
if (monitored) record(s"check eligible refs in ctx", refs.length)
val ownEligible = filterMatching(tp)
if (outerImplicits == NoContext.implicits) ownEligible
if (isOuterMost) ownEligible
else ownEligible ::: {
val shadowed = ownEligible.map(_.ref.name).toSet
outerImplicits.eligible(tp).filterNot(cand => shadowed.contains(cand.ref.name))
Expand All @@ -192,7 +200,7 @@ object Implicits {

override def toString = {
val own = s"(implicits: ${refs mkString ","})"
if (outerImplicits == NoContext.implicits) own else own + "\n " + outerImplicits
if (isOuterMost) own else own + "\n " + outerImplicits
}

/** This context, or a copy, ensuring root import from symbol `root`
Expand Down