Merge pull request #3931 from dotty-staging/fix-#533

Fix #533: Some isAbstractType tests should succeed for parameters

Author: odersky

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

@@ -574,8 +574,11 @@ object Flags {
   /** A synthetic or private definition */
   final val SyntheticOrPrivate = Synthetic | Private
 
-  /** A deferred member or a parameter accessor (these don't have right hand sides) */
-  final val DeferredOrParamOrAccessor = Deferred | Param | ParamAccessor
+  /** A deferred term member or a parameter accessor (these don't have right hand sides) */
+  final val DeferredOrTermParamOrAccessor = Deferred | TermParam | ParamAccessor
+
+  /** A deferred term member or a parameter accessor (these don't have right hand sides) */
+  final val DeferredOrTypeParam = Deferred | TypeParam
 
   /** value that's final or inline */
   final val FinalOrInline = Final | Inline

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

@@ -529,14 +529,17 @@ object SymDenotations {
     }
 
     /** Is this symbol an abstract type? */
-    final def isAbstractType(implicit ctx: Context) = isType && (this is Deferred)
+    final def isAbstractType(implicit ctx: Context) = this is DeferredType
 
     /** Is this symbol an alias type? */
     final def isAliasType(implicit ctx: Context) = isAbstractOrAliasType && !(this is Deferred)
 
     /** Is this symbol an abstract or alias type? */
     final def isAbstractOrAliasType = isType & !isClass
 
+    /** Is this symbol an abstract type or type parameter? */
+    final def isAbstractOrParamType(implicit ctx: Context) = this is DeferredOrTypeParam
+
     /** Is this the denotation of a self symbol of some class?
      *  This is the case if one of two conditions holds:
      *  1. It is the symbol referred to in the selfInfo part of the ClassInfo

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

@@ -211,8 +211,8 @@ object TypeErasure {
     case tp: TypeAlias => isUnboundedGeneric(tp.alias)
     case tp: TypeBounds => !tp.hi.derivesFrom(defn.ObjectClass)
     case tp: TypeProxy => isUnboundedGeneric(tp.underlying)
-    case tp: AndType => isUnboundedGeneric(tp.tp1) || isUnboundedGeneric(tp.tp2)
-    case tp: OrType => isUnboundedGeneric(tp.tp1) && isUnboundedGeneric(tp.tp2)
+    case tp: AndType => isUnboundedGeneric(tp.tp1) && isUnboundedGeneric(tp.tp2)
+    case tp: OrType => isUnboundedGeneric(tp.tp1) || isUnboundedGeneric(tp.tp2)
     case _ => false
   }
 

compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

@@ -368,13 +368,13 @@ class ClassfileParser(
         case ARRAY_TAG =>
           while ('0' <= sig(index) && sig(index) <= '9') index += 1
           var elemtp = sig2type(tparams, skiptvs)
-          // make unbounded Array[T] where T is a type variable into Ar ray[T with Object]
+          // make unbounded Array[T] where T is a type variable into Array[T with Object]
           // (this is necessary because such arrays have a representation which is incompatible
           // with arrays of primitive types.
           // NOTE that the comparison to Object only works for abstract types bounded by classes that are strict subclasses of Object
           // if the bound is exactly Object, it will have been converted to Any, and the comparison will fail
           // see also RestrictJavaArraysMap (when compiling java sources directly)
-          if (elemtp.typeSymbol.isAbstractType && !(elemtp.derivesFrom(defn.ObjectClass))) {
+          if (elemtp.typeSymbol.isAbstractOrParamType && !(elemtp.derivesFrom(defn.ObjectClass))) {
             elemtp = AndType(elemtp, defn.ObjectType)
           }
           defn.ArrayOf(elemtp)

compiler/src/dotty/tools/dotc/core/unpickleScala2/Scala2Unpickler.scala

@@ -66,8 +66,14 @@ object Scala2Unpickler {
       assert(lastArg isRef defn.ArrayClass)
       val elemtp0 :: Nil = lastArg.baseType(defn.ArrayClass).argInfos
       val elemtp = elemtp0 match {
-        case AndType(t1, t2) if t1.typeSymbol.isAbstractType && (t2 isRef defn.ObjectClass) =>
-          t1 // drop intersection with Object for abstract types in varargs. UnCurry can handle them.
+        case AndType(t1, t2) => // drop intersection with Object for abstract types an parameters in varargs. Erasure can handle them.
+          if (t2.isRef(defn.ObjectClass))
+            t1 match {
+              case t1: TypeParamRef => t1
+              case t1: TypeRef if t1.symbol.isAbstractOrParamType => t1
+              case _ => elemtp0
+            }
+          else elemtp0
         case _ =>
           elemtp0
       }

compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala

@@ -427,7 +427,7 @@ object GenericSignatures {
        * owners (e.g. when computing lubs, <root> is used). All packageClass symbols have `isJavaDefined == true`.
        */
       case RefOrAppliedType(sym, tp, _) =>
-        if (sym.isAbstractType && (!sym.owner.is(JavaDefined) || sym.is(Scala2Existential)))
+        if (sym.isAbstractOrParamType && (!sym.owner.is(JavaDefined) || sym.is(Scala2Existential)))
           tp
         else
           NoType

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

@@ -191,7 +191,7 @@ object RefChecks {
       def info = self.memberInfo(sym1)
       val infoStr =
         if (sym1.isAliasType) i", which equals ${info.bounds.hi}"
-        else if (sym1.isAbstractType) i" with bounds$info"
+        else if (sym1.isAbstractOrParamType) i" with bounds$info"
         else if (sym1.is(Module)) ""
         else if (sym1.isTerm) i" of type $info"
         else ""
@@ -913,7 +913,7 @@ class RefChecks extends MiniPhase { thisPhase =>
       }
       def underlyingClass(tp: Type): Symbol = {
         val sym = tp.widen.typeSymbol
-        if (sym.isAbstractType) underlyingClass(sym.info.bounds.hi)
+        if (sym.isAbstractOrParamType) underlyingClass(sym.info.bounds.hi)
         else sym
       }
       val actual   = underlyingClass(other.tpe)

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -1359,7 +1359,7 @@ class Typer extends Namer
       case rhs => typedExpr(rhs, tpt1.tpe)
     }
     val vdef1 = assignType(cpy.ValDef(vdef)(name, tpt1, rhs1), sym)
-    if (sym.is(Inline, butNot = DeferredOrParamOrAccessor))
+    if (sym.is(Inline, butNot = DeferredOrTermParamOrAccessor))
       checkInlineConformant(rhs1, em"right-hand side of inline $sym")
     patchIfLazy(vdef1)
     patchFinalVals(vdef1)

tests/neg/i1747.scala

@@ -1,3 +1,3 @@
-class Coll[E] extends java.util.Collection[E] { // error: needs to be abstract
-  def toArray[T](a: Array[T]): Array[T] = ??? // error: cannot override
+abstract class Coll[E] extends java.util.Collection[E] {
+  override def toArray[T](a: Array[T]): Array[T] = ??? // error: has different signature
 }

tests/pos/i1747.scala

@@ -0,0 +1,3 @@
+abstract class Coll[E] extends java.util.Collection[E] {
+  override def toArray[T](a: Array[T with Object]): Array[T with Object] = ??? // error: cannot override
+}