Bug fixes to make collection strawman compile

compiler/src/dotty/tools/dotc/config/Config.scala

@@ -77,7 +77,7 @@ object Config {
   final val traceDeepSubTypeRecursions = false
 
   /** When explaining subtypes and this flag is set, also show the classes of the compared types. */
-  final val verboseExplainSubtype = true
+  final val verboseExplainSubtype = false
 
   /** If this flag is set, take the fast path when comparing same-named type-aliases and types */
   final val fastPathForRefinedSubtype = true

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -24,7 +24,8 @@ class ScalaSettings extends Settings.SettingGroup {
   val deprecation = BooleanSetting("-deprecation", "Emit warning and location for usages of deprecated APIs.")
   val migration = BooleanSetting("-migration", "Emit warning and location for migration issues from Scala 2.")
   val encoding = StringSetting("-encoding", "encoding", "Specify character encoding used by source files.", Properties.sourceEncoding)
-  val explaintypes = BooleanSetting("-explaintypes", "Explain type errors in more detail.")
+  val explainTypes = BooleanSetting("-explain-types", "Explain type errors in more detail.")
+  val explainImplicits = BooleanSetting("-explain-implicits", "Explain implicit search errors in more detail.")
   val explain = BooleanSetting("-explain", "Explain errors in more detail.")
   val feature = BooleanSetting("-feature", "Emit warning and location for usages of features that should be imported explicitly.")
   val help = BooleanSetting("-help", "Print a synopsis of standard options")
@@ -95,6 +96,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val YforceSbtPhases = BooleanSetting("-Yforce-sbt-phases", "Run the phases used by sbt for incremental compilation (ExtractDependencies and ExtractAPI) even if the compiler is ran outside of sbt, for debugging.")
   val YdumpSbtInc = BooleanSetting("-Ydump-sbt-inc", "For every compiled foo.scala, output the API representation and dependencies used for sbt incremental compilation in foo.inc, implies -Yforce-sbt-phases.")
   val YcheckAllPatmat = BooleanSetting("-Ycheck-all-patmat", "Check exhaustivity and redundancy of all pattern matching (used for testing the algorithm)")
+  val YsuppressParamForwarding = BooleanSetting("-Ysuppress-param-forwarding", "Don't install aliases for base type parameters.")
 
   /** Area-specific debug output */
   val Yexplainlowlevel = BooleanSetting("-Yexplain-lowlevel", "When explaining type errors, show types at a lower level.")

compiler/src/dotty/tools/dotc/core/Mode.scala

@@ -39,6 +39,7 @@ object Mode {
   val TypevarsMissContext = newMode(4, "TypevarsMissContext")
   val CheckCyclic = newMode(5, "CheckCyclic")
 
+  /** We are looking at the arguments of a supercall */
   val InSuperCall = newMode(6, "InSuperCall")
 
   /** Allow GADTFlexType labelled types to have their bounds adjusted */
@@ -81,7 +82,7 @@ object Mode {
   val ReadPositions = newMode(16, "ReadPositions")
 
   val PatternOrType = Pattern | Type
-  
+
   /** We are elaborating the fully qualified name of a package clause.
    *  In this case, identifiers should never be imported.
    */

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

@@ -1381,12 +1381,15 @@ object SymDenotations {
     /** Invalidate baseTypeRefCache, baseClasses and superClassBits on new run */
     private def checkBasesUpToDate()(implicit ctx: Context) =
       if (baseTypeRefValid != ctx.runId) {
-        baseTypeRefCache = new java.util.HashMap[CachedType, Type]
+        invalidateBaseTypeRefCache()
         myBaseClasses = null
         mySuperClassBits = null
         baseTypeRefValid = ctx.runId
       }
 
+    def invalidateBaseTypeRefCache() =
+      baseTypeRefCache = new java.util.HashMap[CachedType, Type]
+
     private def computeBases(implicit ctx: Context): (List[ClassSymbol], BitSet) = {
       if (myBaseClasses eq Nil) throw CyclicReference(this)
       myBaseClasses = Nil
@@ -1712,18 +1715,23 @@ object SymDenotations {
       /*>|>*/ ctx.debugTraceIndented(s"$tp.baseTypeRef($this)") /*<|<*/ {
         tp match {
           case tp: CachedType =>
-            checkBasesUpToDate()
-            var basetp = baseTypeRefCache get tp
-            if (basetp == null) {
-              baseTypeRefCache.put(tp, NoPrefix)
-              basetp = computeBaseTypeRefOf(tp)
-              if (isCachable(tp)) baseTypeRefCache.put(tp, basetp)
-              else baseTypeRefCache.remove(tp)
-            } else if (basetp == NoPrefix) {
-              baseTypeRefCache.put(tp, null)
-              throw CyclicReference(this)
+            try {
+              checkBasesUpToDate()
+              var basetp = baseTypeRefCache get tp
+              if (basetp == null) {
+                baseTypeRefCache.put(tp, NoPrefix)
+                basetp = computeBaseTypeRefOf(tp)
+                if (isCachable(tp)) baseTypeRefCache.put(tp, basetp)
+                else baseTypeRefCache.remove(tp)
+              } else if (basetp == NoPrefix)
+                throw CyclicReference(this)
+              basetp
+            }
+            catch {
+              case ex: Throwable =>
+                baseTypeRefCache.put(tp, null)
+                throw ex
             }
-            basetp
           case _ =>
             computeBaseTypeRefOf(tp)
         }

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

@@ -574,8 +574,15 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
       isNewSubType(tp1.parent, tp2)
     case tp1 @ HKApply(tycon1, args1) =>
       compareHkApply1(tp1, tycon1, args1, tp2)
-    case EtaExpansion(tycon1) =>
-      isSubType(tycon1, tp2)
+    case tp1: HKTypeLambda =>
+      def compareHKLambda = tp1 match {
+        case EtaExpansion(tycon1) => isSubType(tycon1, tp2)
+        case _ => tp2 match {
+          case tp2: HKTypeLambda => false // this case was covered in thirdTry
+          case _ => tp2.isHK && isSubType(tp1.resultType, tp2.appliedTo(tp1.paramRefs))
+        }
+      }
+      compareHKLambda
     case AndType(tp11, tp12) =>
       // Rewrite (T111 | T112) & T12 <: T2 to (T111 & T12) <: T2 and (T112 | T12) <: T2
       // and analogously for T11 & (T121 | T122) & T12 <: T2
@@ -775,7 +782,7 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
           (v < 0 || isSubType(tp1, tp2))
       }
       isSub(args1.head, args2.head)
-    } && isSubArgs(args1.tail, args2.tail, tparams)
+    } && isSubArgs(args1.tail, args2.tail, tparams.tail)
 
   /** Test whether `tp1` has a base type of the form `B[T1, ..., Tn]` where
    *   - `B` derives from one of the class symbols of `tp2`,
@@ -1287,8 +1294,7 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
           tl.integrate(tparams1, tparam1.paramInfoAsSeenFrom(tp1)).bounds &
           tl.integrate(tparams2, tparam2.paramInfoAsSeenFrom(tp2)).bounds),
         resultTypeExp = tl =>
-          original(tl.integrate(tparams1, tp1).appliedTo(tl.paramRefs),
-             tl.integrate(tparams2, tp2).appliedTo(tl.paramRefs)))
+          original(tp1.appliedTo(tl.paramRefs), tp2.appliedTo(tl.paramRefs)))
   }
 
   /** Try to distribute `&` inside type, detect and handle conflicts

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

@@ -321,72 +321,11 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
     }
   }
 
-  /** If we have member definitions
-   *
-   *     type argSym v= from
-   *     type from v= to
-   *
-   *  where the variances of both alias are the same, then enter a new definition
-   *
-   *     type argSym v= to
-   *
-   *  unless a definition for `argSym` already exists in the current scope.
-   */
-  def forwardRef(argSym: Symbol, from: Symbol, to: TypeBounds, cls: ClassSymbol, decls: Scope) =
-    argSym.info match {
-      case info @ TypeBounds(lo2 @ TypeRef(_: ThisType, name), hi2) =>
-        if (name == from.name &&
-            (lo2 eq hi2) &&
-            info.variance == to.variance &&
-            !decls.lookup(argSym.name).exists) {
-              // println(s"short-circuit ${argSym.name} was: ${argSym.info}, now: $to")
-              enterArgBinding(argSym, to, cls, decls)
-            }
-      case _ =>
-    }
-
-
   /** Normalize a list of parent types of class `cls` that may contain refinements
    *  to a list of typerefs referring to classes, by converting all refinements to member
    *  definitions in scope `decls`. Can add members to `decls` as a side-effect.
    */
   def normalizeToClassRefs(parents: List[Type], cls: ClassSymbol, decls: Scope): List[TypeRef] = {
-
-    /** If we just entered the type argument binding
-     *
-     *    type From = To
-     *
-     *  and there is a type argument binding in a parent in `prefs` of the form
-     *
-     *    type X = From
-     *
-     *  then also add the binding
-     *
-     *    type X = To
-     *
-     *  to the current scope, provided (1) variances of both aliases are the same, and
-     *  (2) X is not yet defined in current scope. This "short-circuiting" prevents
-     *  long chains of aliases which would have to be traversed in type comparers.
-     *
-     *  Note: Test i1401.scala shows that `forwardRefs` is also necessary
-     *  for typechecking in the case where self types refer to type parameters
-     *  that are upper-bounded by subclass instances.
-     */
-    def forwardRefs(from: Symbol, to: Type, prefs: List[TypeRef]) = to match {
-      case to @ TypeBounds(lo1, hi1) if lo1 eq hi1 =>
-        for (pref <- prefs) {
-          def forward()(implicit ctx: Context): Unit =
-            for (argSym <- pref.decls)
-              if (argSym is BaseTypeArg)
-                forwardRef(argSym, from, to, cls, decls)
-          pref.info match {
-            case info: TempClassInfo => info.addSuspension(implicit ctx => forward())
-            case _ => forward()
-          }
-        }
-      case _ =>
-    }
-
     // println(s"normalizing $parents of $cls in ${cls.owner}") // !!! DEBUG
 
     // A map consolidating all refinements arising from parent type parameters
@@ -429,16 +368,70 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
         s"redefinition of ${decls.lookup(name).debugString} in ${cls.showLocated}")
       enterArgBinding(formals(name), refinedInfo, cls, decls)
     }
-    // Forward definitions in super classes that have one of the refined parameters
-    // as aliases directly to the refined info.
-    // Note that this cannot be fused with the previous loop because we now
-    // assume that all arguments have been entered in `decls`.
-    refinements foreachBinding { (name, refinedInfo) =>
-      forwardRefs(formals(name), refinedInfo, parentRefs)
-    }
+
+    if (!ctx.settings.YsuppressParamForwarding.value)
+      forwardParamBindings(parentRefs, refinements, cls, decls)
+
     parentRefs
   }
 
+  /** Forward parameter bindings in baseclasses to argument types of
+   *  class `cls` if possible.
+   *  If there have member definitions
+   *
+   *     type param v= middle
+   *     type middle v= to
+   *
+   *  where the variances of both alias are the same, then enter a new definition
+   *
+   *     type param v= to
+   *
+   *  If multiple forwarders would be generated, join their `to` types with an `&`.
+   *
+   *  @param cls           The class for which parameter bindings should be forwarded
+   *  @param decls	       Its scope
+   *  @param parentRefs    The parent type references of `cls`
+   *  @param paramBindings The type parameter bindings generated for `cls`
+   *
+   */
+  def forwardParamBindings(parentRefs: List[TypeRef],
+                           paramBindings: SimpleMap[TypeName, Type],
+                           cls: ClassSymbol, decls: Scope)(implicit ctx: Context) = {
+
+    def forwardRef(argSym: Symbol, from: TypeName, to: TypeAlias) = argSym.info match {
+      case info @ TypeAlias(TypeRef(_: ThisType, `from`)) if info.variance == to.variance =>
+        val existing = decls.lookup(argSym.name)
+        if (existing.exists) existing.info = existing.info & to
+        else enterArgBinding(argSym, to, cls, decls)
+      case _ =>
+    }
+
+    def forwardRefs(from: TypeName, to: Type) = to match {
+      case to: TypeAlias =>
+        for (pref <- parentRefs) {
+          def forward()(implicit ctx: Context): Unit =
+            for (argSym <- pref.decls)
+              if (argSym is BaseTypeArg) forwardRef(argSym, from, to)
+          pref.info match {
+            case info: TempClassInfo => info.addSuspension(implicit ctx => forward())
+            case _ => forward()
+          }
+        }
+      case _ =>
+    }
+
+    paramBindings.foreachBinding(forwardRefs)
+  }
+
+  /** Used only for debugging: All BaseTypeArg definitions in
+   *  `cls` and all its base classes.
+   */
+  def allBaseTypeArgs(cls: ClassSymbol)(implicit ctx: Context) =
+    for { bc <- cls.baseClasses
+          sym <- bc.info.decls.toList
+          if sym.is(BaseTypeArg)
+    } yield sym
+
   /** An argument bounds violation is a triple consisting of
    *   - the argument tree
    *   - a string "upper" or "lower" indicating which bound is violated

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -3030,6 +3030,8 @@ object Types {
     override def hashCode: Int = identityHash
     override def equals(that: Any) = this eq that.asInstanceOf[AnyRef]
 
+    def withName(name: Name): this.type = { myRepr = name; this }
+
     private var myRepr: Name = null
     def repr(implicit ctx: Context): Name = {
       if (myRepr == null) myRepr = SkolemName.fresh()

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -119,24 +119,26 @@ class TreePickler(pickler: TastyPickler) {
       pickleType(c.symbolValue.termRef)
   }
 
-  def pickleType(tpe0: Type, richTypes: Boolean = false)(implicit ctx: Context): Unit = try {
+  def pickleType(tpe0: Type, richTypes: Boolean = false)(implicit ctx: Context): Unit = {
     val tpe = tpe0.stripTypeVar
-    val prev = pickledTypes.get(tpe)
-    if (prev == null) {
-      pickledTypes.put(tpe, currentAddr)
-      pickleNewType(tpe, richTypes)
-    }
-    else {
-      writeByte(SHARED)
-      writeRef(prev.asInstanceOf[Addr])
+    try {
+      val prev = pickledTypes.get(tpe)
+      if (prev == null) {
+        pickledTypes.put(tpe, currentAddr)
+        pickleNewType(tpe, richTypes)
+      }
+      else {
+        writeByte(SHARED)
+        writeRef(prev.asInstanceOf[Addr])
+      }
+    } catch {
+      case ex: AssertionError =>
+        println(i"error when pickling type $tpe")
+        throw ex
     }
-  } catch {
-    case ex: AssertionError =>
-      println(i"error when pickling type $tpe0")
-      throw ex
   }
 
-  private def pickleNewType(tpe: Type, richTypes: Boolean)(implicit ctx: Context): Unit = try { tpe match {
+  private def pickleNewType(tpe: Type, richTypes: Boolean)(implicit ctx: Context): Unit = tpe match {
     case AppliedType(tycon, args) =>
       writeByte(APPLIEDtype)
       withLength { pickleType(tycon); args.foreach(pickleType(_)) }
@@ -241,21 +243,10 @@ class TreePickler(pickler: TastyPickler) {
       pickleMethodic(POLYtype, tpe)
     case tpe: MethodType if richTypes =>
       pickleMethodic(METHODtype, tpe)
-    case tpe: TypeParamRef =>
-      if (!pickleParamRef(tpe))
-      // TODO figure out why this case arises in e.g. pickling AbstractFileReader.
-        ctx.typerState.constraint.entry(tpe) match {
-          case TypeBounds(lo, hi) if lo eq hi => pickleNewType(lo, richTypes)
-          case _ => assert(false, s"orphan poly parameter: $tpe")
-        }
-    case tpe: TermParamRef =>
-      assert(pickleParamRef(tpe), s"orphan method parameter: $tpe")
+    case tpe: ParamRef =>
+      assert(pickleParamRef(tpe), s"orphan parameter reference: $tpe")
     case tpe: LazyRef =>
       pickleType(tpe.ref)
-  }} catch {
-    case ex: AssertionError =>
-      println(i"error while pickling type $tpe")
-      throw ex
   }
 
   def picklePackageRef(pkg: Symbol)(implicit ctx: Context): Unit = {

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -174,7 +174,7 @@ class PlainPrinter(_ctx: Context) extends Printer {
         def paramText(name: Name, bounds: TypeBounds): Text = name.toString ~ toText(bounds)
         changePrec(GlobalPrec) {
           "[" ~ Text((tp.paramNames, tp.paramInfos).zipped.map(paramText), ", ") ~
-          "]" ~ (" => " provided !tp.resultType.isInstanceOf[MethodType]) ~
+          "]" ~ lambdaHash(tp) ~ (" => " provided !tp.resultType.isInstanceOf[MethodType]) ~
           toTextGlobal(tp.resultType)
         }
       case tp: TypeParamRef =>