Merge pull request #238 from dotty-staging/fix/bounds-propagation-v2

Fix/bounds propagation v2

Author: odersky

src/dotty/tools/dotc/core/SymDenotations.scala

@@ -432,7 +432,7 @@ object SymDenotations {
     final def isSetter(implicit ctx: Context) =
       (this is Accessor) &&
       originalName.isSetterName &&
-      info.firstParamTypes.nonEmpty // to avoid being fooled by   var x_= : Unit = ...
+      (!isCompleted || info.firstParamTypes.nonEmpty) // to avoid being fooled by   var x_= : Unit = ...
 
     /** is this the constructor of a class? */
     final def isClassConstructor = name == nme.CONSTRUCTOR

src/dotty/tools/dotc/core/TypeApplications.scala

@@ -293,8 +293,9 @@ class TypeApplications(val self: Type) extends AnyVal {
   /** If this is an encoding of a (partially) applied type, return its arguments,
    *  otherwise return Nil.
    *  Existential types in arguments are returned as TypeBounds instances.
+   *  @param interpolate   See argInfo
    */
-  final def argInfos(implicit ctx: Context): List[Type] = {
+  final def argInfos(interpolate: Boolean)(implicit ctx: Context): List[Type] = {
     var tparams: List[TypeSymbol] = null
     def recur(tp: Type, refineCount: Int): mutable.ListBuffer[Type] = tp.stripTypeVar match {
       case tp @ RefinedType(tycon, name) =>
@@ -304,7 +305,7 @@ class TypeApplications(val self: Type) extends AnyVal {
           if (tparams == null) tparams = tycon.typeParams
           if (buf.size < tparams.length) {
             val tparam = tparams(buf.size)
-            if (name == tparam.name) buf += tp.refinedInfo.argInfo(tparam)
+            if (name == tparam.name) buf += tp.refinedInfo.argInfo(tparam, interpolate)
             else null
           } else null
         }
@@ -316,6 +317,8 @@ class TypeApplications(val self: Type) extends AnyVal {
     if (buf == null) Nil else buf.toList
   }
 
+  final def argInfos(implicit ctx: Context): List[Type] = argInfos(interpolate = true)
+
   /** Argument types where existential types in arguments are disallowed */
   def argTypes(implicit ctx: Context) = argInfos mapConserve noBounds
 
@@ -338,16 +341,27 @@ class TypeApplications(val self: Type) extends AnyVal {
 
   /** If this is the image of a type argument to type parameter `tparam`,
    *  recover the type argument, otherwise NoType.
+   *  @param interpolate   If true, replace type bounds as arguments corresponding to
+   *                       variant type parameters by their dominating element. I.e. an argument
+   *
+   *                           T <: U
+   *
+   *                       for a covariant type-parameter becomes U, and an argument
+   *
+   *                           T >: L
+   *
+   *                       for a contravariant type-parameter becomes L.
    */
-  final def argInfo(tparam: Symbol)(implicit ctx: Context): Type = self match {
+  final def argInfo(tparam: Symbol, interpolate: Boolean = true)(implicit ctx: Context): Type = self match {
     case TypeBounds(lo, hi) =>
       if (lo eq hi) hi
-      else {
+      else if (interpolate) {
         val v = tparam.variance
         if (v > 0 && (lo isRef defn.NothingClass)) hi
         else if (v < 0 && (hi isRef defn.AnyClass)) lo
-        else self // it's wildcard type; return its bounds
+        else self
       }
+      else self
     case _ =>
       NoType
   }

src/dotty/tools/dotc/core/TypeComparer.scala

@@ -307,6 +307,11 @@ class TypeComparer(initctx: Context) extends DotClass {
     }
   }
 
+  private def narrowRefined(tp: Type): Type = tp match {
+    case tp: RefinedType => RefinedThis(tp)
+    case _ => tp
+  }
+
   /** If the prefix of a named type is `this` (i.e. an instance of type
    *  `ThisType` or `RefinedThis`), and there is a refinement type R that
    *  "refines" (transitively contains as its parent) a class reference
@@ -650,52 +655,54 @@ class TypeComparer(initctx: Context) extends DotClass {
       }
       compareNamed
     case tp2 @ RefinedType(parent2, name2) =>
+        def qualifies(m: SingleDenotation) = isSubType(m.info, tp2.refinedInfo)
+        def memberMatches(mbr: Denotation): Boolean = mbr match { // inlined hasAltWith for performance
+          case mbr: SingleDenotation => qualifies(mbr)
+          case _ => mbr hasAltWith qualifies
+        }
+      def compareRefinedSlow: Boolean = {
+        def hasMatchingMember(name: Name): Boolean = /*>|>*/ ctx.traceIndented(s"hasMatchingMember($name) ${tp1.member(name).info.show}", subtyping) /*<|<*/ {
+          val tp1r = rebaseQual(tp1, name)
+          (memberMatches(narrowRefined(tp1r) member name)
+            ||
+            { // special case for situations like:
+              //    foo <: C { type T = foo.T }
+              tp2.refinedInfo match {
+                case TypeBounds(lo, hi) if lo eq hi =>
+                  !ctx.phase.erasedTypes && (tp1r select name) =:= lo
+                case _ => false
+              }
+            })
+        }
+        val matchesParent = {
+          val saved = pendingRefinedBases
+          try {
+            addPendingName(name2, tp2, tp2)
+            isSubType(tp1, parent2)
+          } finally pendingRefinedBases = saved
+        }
+        (matchesParent && (
+          name2 == nme.WILDCARD
+          || hasMatchingMember(name2)
+          || fourthTry(tp1, tp2))
+          || needsEtaLift(tp1, tp2) && tp1.testLifted(tp2.typeParams, isSubType(_, tp2)))
+      }
       def compareRefined: Boolean = tp1.widen match {
         case tp1 @ RefinedType(parent1, name1) if name1 == name2 && name1.isTypeName =>
-          // optimized case; all info on tp1.name1 is in refinement tp1.refinedInfo.
-          isSubType(normalizedInfo(tp1), tp2.refinedInfo) && {
-            val saved = pendingRefinedBases
-            try {
-              addPendingName(name1, tp1, tp2)
-              isSubType(parent1, parent2)
-            }
-            finally pendingRefinedBases = saved
+          normalizedInfo(tp1) match {
+            case bounds1 @ TypeBounds(lo1, hi1) if lo1 eq hi1 =>
+              isSubType(bounds1, tp2.refinedInfo) && {
+                val saved = pendingRefinedBases
+                try {
+                  addPendingName(name1, tp1, tp2)
+                  isSubType(parent1, parent2)
+                } finally pendingRefinedBases = saved
+              }
+            case _ =>
+              compareRefinedSlow
           }
         case _ =>
-          def qualifies(m: SingleDenotation) = isSubType(m.info, tp2.refinedInfo)
-          def memberMatches(mbr: Denotation): Boolean = mbr match { // inlined hasAltWith for performance
-            case mbr: SingleDenotation => qualifies(mbr)
-            case _ => mbr hasAltWith qualifies
-          }
-          def hasMatchingMember(name: Name): Boolean = /*>|>*/ ctx.traceIndented(s"hasMatchingMember($name) ${tp1.member(name).info.show}", subtyping) /*<|<*/ {
-            val tp1r = rebaseQual(tp1, name)
-            (  memberMatches(tp1r member name)
-            ||
-               { // special case for situations like:
-                 //    foo <: C { type T = foo.T }
-                 tp2.refinedInfo match {
-                   case TypeBounds(lo, hi) if lo eq hi =>
-                     !ctx.phase.erasedTypes && (tp1r select name) =:= lo
-                   case _ => false
-                 }
-               }
-            )
-          }
-          val matchesParent = {
-            val saved = pendingRefinedBases
-            try {
-              addPendingName(name2, tp2, tp2)
-              isSubType(tp1, parent2)
-            }
-            finally pendingRefinedBases = saved
-          }
-          (  matchesParent && (
-                name2 == nme.WILDCARD
-             || hasMatchingMember(name2)
-             || fourthTry(tp1, tp2)
-             )
-          || needsEtaLift(tp1, tp2) && tp1.testLifted(tp2.typeParams, isSubType(_, tp2))
-          )
+          compareRefinedSlow
       }
       compareRefined
     case OrType(tp21, tp22) =>

src/dotty/tools/dotc/core/TypeOps.scala

@@ -7,12 +7,14 @@ import config.Printers._
 import Decorators._
 import StdNames._
 import util.SimpleMap
+import collection.mutable
+import ast.tpd._
 
 trait TypeOps { this: Context =>
 
   final def asSeenFrom(tp: Type, pre: Type, cls: Symbol, theMap: AsSeenFromMap): Type = {
 
-    def toPrefix(pre: Type, cls: Symbol, thiscls: ClassSymbol): Type = /*>|>*/ ctx.debugTraceIndented(s"toPrefix($pre, $cls, $thiscls)") /*<|<*/ {
+    def toPrefix(pre: Type, cls: Symbol, thiscls: ClassSymbol): Type = /*>|>*/ ctx.conditionalTraceIndented(TypeOps.track, s"toPrefix($pre, $cls, $thiscls)") /*<|<*/ {
       if ((pre eq NoType) || (pre eq NoPrefix) || (cls is PackageClass))
         tp
       else if (thiscls.derivesFrom(cls) && pre.baseTypeRef(thiscls).exists)
@@ -24,7 +26,7 @@ trait TypeOps { this: Context =>
         toPrefix(pre.baseTypeRef(cls).normalizedPrefix, cls.owner, thiscls)
     }
 
-    /*>|>*/ ctx.conditionalTraceIndented(TypeOps.track , s"asSeen ${tp.show} from (${pre.show}, ${cls.show})", show = true) /*<|<*/ { // !!! DEBUG
+    /*>|>*/ ctx.conditionalTraceIndented(TypeOps.track, s"asSeen ${tp.show} from (${pre.show}, ${cls.show})", show = true) /*<|<*/ { // !!! DEBUG
       tp match {
         case tp: NamedType =>
           val sym = tp.symbol
@@ -56,7 +58,13 @@ trait TypeOps { this: Context =>
   final def simplify(tp: Type, theMap: SimplifyMap): Type = tp match {
     case tp: NamedType =>
       if (tp.symbol.isStatic) tp
-      else tp.derivedSelect(simplify(tp.prefix, theMap))
+      else tp.derivedSelect(simplify(tp.prefix, theMap)) match {
+        case tp1: NamedType if tp1.denotationIsCurrent =>
+          val tp2 = tp1.reduceProjection
+          //if (tp2 ne tp1) println(i"simplified $tp1 -> $tp2")
+          tp2
+        case tp1 => tp1
+      }
     case tp: PolyParam =>
       typerState.constraint.typeVarOfParam(tp) orElse tp
     case  _: ThisType | _: BoundType | NoPrefix =>
@@ -301,6 +309,40 @@ trait TypeOps { this: Context =>
     parentRefs
   }
 
+  /** An argument bounds violation is a triple consisting of
+   *   - the argument tree
+   *   - a string "upper" or "lower" indicating which bound is violated
+   *   - the violated bound
+   */
+  type BoundsViolation = (Tree, String, Type)
+
+  /** The list of violations where arguments are not within bounds.
+   *  @param  args          The arguments
+   *  @param  boundss       The list of type bounds
+   *  @param  instantiate   A function that maps a bound type and the list of argument types to a resulting type.
+   *                        Needed to handle bounds that refer to other bounds.
+   */
+  def boundsViolations(args: List[Tree], boundss: List[TypeBounds], instantiate: (Type, List[Type]) => Type)(implicit ctx: Context): List[BoundsViolation] = {
+    val argTypes = args.tpes
+    val violations = new mutable.ListBuffer[BoundsViolation]
+    for ((arg, bounds) <- args zip boundss) {
+      def checkOverlapsBounds(lo: Type, hi: Type): Unit = {
+        //println(i"instantiating ${bounds.hi} with $argTypes")
+        //println(i" = ${instantiate(bounds.hi, argTypes)}")
+        val hiBound = instantiate(bounds.hi, argTypes.mapConserve(_.bounds.hi))
+          // Note that argTypes can contain a TypeBounds type for arguments that are
+          // not fully determined. In that case we need to check against the hi bound of the argument.
+        if (!(lo <:< hiBound)) violations += ((arg, "upper", hiBound))
+        if (!(bounds.lo <:< hi)) violations += ((arg, "lower", bounds.lo))
+      }
+      arg.tpe match {
+        case TypeBounds(lo, hi) => checkOverlapsBounds(lo, hi)
+        case tp => checkOverlapsBounds(tp, tp)
+      }
+    }
+    violations.toList
+  }
+
   /** Is `feature` enabled in class `owner`?
    *  This is the case if one of the following two alternatives holds:
    *