diff options
Diffstat (limited to 'src/reflect')
| -rw-r--r-- | src/reflect/scala/reflect/internal/Types.scala | 60 |
1 files changed, 40 insertions, 20 deletions
diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala index bfd18f6a43..c2637e6967 100644 --- a/src/reflect/scala/reflect/internal/Types.scala +++ b/src/reflect/scala/reflect/internal/Types.scala @@ -593,6 +593,26 @@ trait Types extends api.Types { self: SymbolTable => /** Expands type aliases. */ def dealias = this + /** Repeatedly apply widen and dealias until they have no effect. + * This compensates for the fact that type aliases can hide beneath + * singleton types and singleton types can hide inside type aliases. + */ + def dealiasWiden: Type = ( + if (this ne widen) widen.dealiasWiden + else if (this ne dealias) dealias.dealiasWiden + else this + ) + + /** All the types encountered in the course of dealiasing/widening, + * including each intermediate beta reduction step (whereas calling + * dealias applies as many as possible.) + */ + def dealiasWidenChain: List[Type] = this :: ( + if (this ne widen) widen.dealiasWidenChain + else if (this ne betaReduce) betaReduce.dealiasWidenChain + else Nil + ) + def etaExpand: Type = this /** Performs a single step of beta-reduction on types. @@ -3173,23 +3193,20 @@ 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 @@ -3282,7 +3299,7 @@ trait Types extends api.Types { self: SymbolTable => if (constr.instValid) constr.inst // get here when checking higher-order subtyping of the typevar by itself // TODO: check whether this ever happens? - else if (isHigherKinded) typeFun(params, applyArgs(params map (_.typeConstructor))) + else if (isHigherKinded) logResult("Normalizing HK $this")(typeFun(params, applyArgs(params map (_.typeConstructor)))) else super.normalize ) override def typeSymbol = origin.typeSymbol @@ -3754,7 +3771,7 @@ trait Types extends api.Types { self: SymbolTable => def existentialAbstraction(tparams: List[Symbol], tpe0: Type): Type = if (tparams.isEmpty) tpe0 else { - val tpe = deAlias(tpe0) + val tpe = normalizeAliases(tpe0) val tpe1 = new ExistentialExtrapolation(tparams) extrapolate tpe var tparams0 = tparams var tparams1 = tparams0 filter tpe1.contains @@ -3768,13 +3785,16 @@ trait Types extends api.Types { self: SymbolTable => newExistentialType(tparams1, tpe1) } - /** Remove any occurrences of type aliases from this type */ - object deAlias extends TypeMap { - def apply(tp: Type): Type = mapOver { - tp match { - case TypeRef(pre, sym, args) if sym.isAliasType => tp.normalize - case _ => tp - } + /** Normalize any type aliases within this type (@see Type#normalize). + * Note that this depends very much on the call to "normalize", not "dealias", + * so it is no longer carries the too-stealthy name "deAlias". + */ + object normalizeAliases extends TypeMap { + def apply(tp: Type): Type = tp match { + case TypeRef(_, sym, _) if sym.isAliasType => + def msg = if (tp.isHigherKinded) s"Normalizing type alias function $tp" else s"Dealiasing type alias $tp" + mapOver(logResult(msg)(tp.normalize)) + case _ => mapOver(tp) } } |