diff options
| -rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/Implicits.scala | 103 | ||||
| -rw-r--r-- | test/files/neg/divergent-implicit.check | 6 | ||||
| -rw-r--r-- | test/files/pos/t8460.scala | 25 |
3 files changed, 92 insertions, 42 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala index 1a38fcf3a4..d87090fa46 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Implicits.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Implicits.scala @@ -833,19 +833,41 @@ trait Implicits { * so that if there is a best candidate it can still be selected. */ object DivergentImplicitRecovery { - // symbol of the implicit that caused the divergence. - // Initially null, will be saved on first diverging expansion. - private var implicitSym: Symbol = _ - private var countdown: Int = 1 - - def sym: Symbol = implicitSym - def apply(search: SearchResult, i: ImplicitInfo): SearchResult = - if (search.isDivergent && countdown > 0) { - countdown -= 1 - implicitSym = i.sym - log(s"discarding divergent implicit $implicitSym during implicit search") + private var divergentError: Option[DivergentImplicitTypeError] = None + + private def saveDivergent(err: DivergentImplicitTypeError) { + if (divergentError.isEmpty) divergentError = Some(err) + } + + def issueSavedDivergentError() { + divergentError foreach (err => context.issue(err)) + } + + def apply(search: SearchResult, i: ImplicitInfo, errors: Seq[AbsTypeError]): SearchResult = { + // A divergent error from a nested implicit search will be found in `errors`. Stash that + // aside to be re-issued if this implicit search fails. + errors.collectFirst { case err: DivergentImplicitTypeError => err } foreach saveDivergent + + if (search.isDivergent && divergentError.isEmpty) { + // Divergence triggered by `i` at this level of the implicit serach. We haven't + // seen divergence so far, we won't issue this error just yet, and instead temporarily + // treat `i` as a failed candidate. + saveDivergent(DivergentImplicitTypeError(tree, pt, i.sym)) + log(s"discarding divergent implicit ${i.sym} during implicit search") SearchFailure - } else search + } else { + if (search.isFailure) { + // We don't want errors that occur during checking implicit info + // to influence the check of further infos, but we should retain divergent implicit errors + // (except for the one we already squirreled away) + val saved = divergentError.getOrElse(null) + context.reportBuffer.retainErrors { + case err: DivergentImplicitTypeError => err ne saved + } + } + search + } + } } /** Sorted list of eligible implicits. @@ -869,31 +891,33 @@ trait Implicits { * - if it matches, forget about all others it improves upon */ @tailrec private def rankImplicits(pending: Infos, acc: Infos): Infos = pending match { - case Nil => acc - case i :: is => - DivergentImplicitRecovery(typedImplicit(i, ptChecked = true, isLocalToCallsite), i) match { - case sr if sr.isDivergent => - Nil - case sr if sr.isFailure => - // We don't want errors that occur during checking implicit info - // to influence the check of further infos. - context.reportBuffer.retainErrors { - case err: DivergentImplicitTypeError => true + case Nil => acc + case firstPending :: otherPending => + def firstPendingImproves(alt: ImplicitInfo) = + firstPending == alt || ( + try improves(firstPending, alt) + catch { + case e: CyclicReference => + debugwarn(s"Discarding $firstPending during implicit search due to cyclic reference.") + true } - rankImplicits(is, acc) - case newBest => - best = newBest - val newPending = undoLog undo { - is filterNot (alt => alt == i || { - try improves(i, alt) - catch { - case e: CyclicReference => - debugwarn(s"Discarding $i during implicit search due to cyclic reference") - true - } - }) + ) + + val typedFirstPending = typedImplicit(firstPending, ptChecked = true, isLocalToCallsite) + + // Pass the errors to `DivergentImplicitRecovery` so that it can note + // the first `DivergentImplicitTypeError` that is being propagated + // from a nested implicit search; this one will be + // re-issued if this level of the search fails. + DivergentImplicitRecovery(typedFirstPending, firstPending, context.errors) match { + case sr if sr.isDivergent => Nil + case sr if sr.isFailure => rankImplicits(otherPending, acc) + case newBest => + best = newBest // firstPending is our new best, since we already pruned last time around: + val pendingImprovingBest = undoLog undo { + otherPending filterNot firstPendingImproves } - rankImplicits(newPending, i :: acc) + rankImplicits(pendingImprovingBest, firstPending :: acc) } } @@ -921,12 +945,9 @@ trait Implicits { } if (best.isFailure) { - /* If there is no winner, and we witnessed and caught divergence, - * now we can throw it for the error message. - */ - if (DivergentImplicitRecovery.sym != null) { - DivergingImplicitExpansionError(tree, pt, DivergentImplicitRecovery.sym)(context) - } + // If there is no winner, and we witnessed and recorded a divergence error, + // our recovery attempt has failed, so we must now issue it. + DivergentImplicitRecovery.issueSavedDivergentError() if (invalidImplicits.nonEmpty) setAddendum(pos, () => diff --git a/test/files/neg/divergent-implicit.check b/test/files/neg/divergent-implicit.check index 60d876409f..d4a3ddfc71 100644 --- a/test/files/neg/divergent-implicit.check +++ b/test/files/neg/divergent-implicit.check @@ -3,6 +3,10 @@ divergent-implicit.scala:4: error: type mismatch; required: String val x1: String = 1 ^ +divergent-implicit.scala:5: error: diverging implicit expansion for type Int => String +starting with method $conforms in object Predef + val x2: String = cast[Int, String](1) + ^ divergent-implicit.scala:14: error: type mismatch; found : Test2.Foo required: Test2.Bar @@ -13,4 +17,4 @@ divergent-implicit.scala:15: error: type mismatch; required: Test2.Bar val y: Bar = new Baz ^ -three errors found +four errors found diff --git a/test/files/pos/t8460.scala b/test/files/pos/t8460.scala new file mode 100644 index 0000000000..10d2ed432c --- /dev/null +++ b/test/files/pos/t8460.scala @@ -0,0 +1,25 @@ +object tan extends UFunc { + implicit def ImplDouble: Impl[Double, Double] = ??? +} + +trait UFunc { + trait TC[+A] + type Impl[V, VR] = UFunc.UImpl[this.type, V, VR] +} + +object UFunc { + class UImpl[A, B, C] + implicit def implicitDoubleUTag[Tag, V, VR](implicit conv: V=>Double, impl: UImpl[Tag, Double, VR]):UImpl[Tag, V, VR] = ??? + +} + +object Test { + implicitly[tan.Impl[Double, Double]] + // we should discard the one and only divergent implicit (`implicitDoubleUTag`) + // This is done under `scalac-hash v2.10.4 test.scala`, but not under + // `scalac-hash v2.10.4 -Xdivergence211 test.scala` + // + // This seems to be because the companion implicits contain redundant entries + // + +} |