diff options
| -rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/Infer.scala | 6 | ||||
| -rw-r--r-- | src/reflect/scala/reflect/internal/Types.scala | 19 | ||||
| -rw-r--r-- | test/files/pos/t6846.scala | 28 |
3 files changed, 40 insertions, 13 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala index a43dbae1fa..7188290688 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala @@ -1122,15 +1122,17 @@ trait Infer extends Checkable { */ def inferExprInstance(tree: Tree, tparams: List[Symbol], pt: Type = WildcardType, treeTp0: Type = null, keepNothings: Boolean = true, useWeaklyCompatible: Boolean = false): List[Symbol] = { val treeTp = if(treeTp0 eq null) tree.tpe else treeTp0 // can't refer to tree in default for treeTp0 + val (targs, tvars) = exprTypeArgs(tparams, treeTp, pt, useWeaklyCompatible) printInference( ptBlock("inferExprInstance", "tree" -> tree, "tree.tpe"-> tree.tpe, "tparams" -> tparams, - "pt" -> pt + "pt" -> pt, + "targs" -> targs, + "tvars" -> tvars ) ) - val (targs, tvars) = exprTypeArgs(tparams, treeTp, pt, useWeaklyCompatible) if (keepNothings || (targs eq null)) { //@M: adjustTypeArgs fails if targs==null, neg/t0226 substExpr(tree, tparams, targs, pt) diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala index 7a63699259..c121c6020e 100644 --- a/src/reflect/scala/reflect/internal/Types.scala +++ b/src/reflect/scala/reflect/internal/Types.scala @@ -3144,23 +3144,20 @@ trait Types extends api.Types { self: SymbolTable => * Checks subtyping of higher-order type vars, and uses variances as defined in the * type parameter we're trying to infer (the result will be sanity-checked later). */ - def unifyFull(tpe: Type) = { - // The alias/widen variations are often no-ops. - val tpes = ( - if (isLowerBound) List(tpe, tpe.widen, tpe.dealias, tpe.widen.dealias).distinct - else List(tpe) - ) - tpes exists { tp => - val lhs = if (isLowerBound) tp.typeArgs else typeArgs - val rhs = if (isLowerBound) typeArgs else tp.typeArgs - - sameLength(lhs, rhs) && { + def unifyFull(tpe: Type): Boolean = { + def unifySpecific(tp: Type) = { + sameLength(typeArgs, tp.typeArgs) && { + val lhs = if (isLowerBound) tp.typeArgs else typeArgs + val rhs = if (isLowerBound) typeArgs else tp.typeArgs // this is a higher-kinded type var with same arity as tp. // side effect: adds the type constructor itself as a bound addBound(tp.typeConstructor) isSubArgs(lhs, rhs, params, AnyDepth) } } + // The type with which we can successfully unify can be hidden + // behind singleton types and type aliases. + tpe.dealiasWidenChain exists unifySpecific } // There's a <: test taking place right now, where tp is a concrete type and this is a typevar diff --git a/test/files/pos/t6846.scala b/test/files/pos/t6846.scala new file mode 100644 index 0000000000..009566493f --- /dev/null +++ b/test/files/pos/t6846.scala @@ -0,0 +1,28 @@ +object Test { + class Arb[_] + implicit def foo[M[_], A]: Arb[M[A]] = null + foo: Arb[List[Int]] + type ListInt = List[Int] + foo: Arb[ListInt] +} + +object Test2 { + import scala.collection.immutable.List + + class Carb[_] + implicit def narrow[N, M[_], A](x: Carb[M[A]])(implicit ev: N <:< M[A]): Carb[N] = null + implicit def bar[M[_], A]: Carb[M[A]] = null + + type ListInt = List[Int] + + val x: List[Int] = List(1) + val y: ListInt = List(1) + + type ListSingletonX = x.type + type ListSingletonY = y.type + + bar: Carb[List[Int]] + bar: Carb[ListInt] + bar: Carb[ListSingletonX] + bar: Carb[ListSingletonY] +} |