ObjectTpeJava part 2

Make sure the TypeRef is truly unique, even when embedded
in other types, such as a TypeBounds. Since we're dealing
with structural equality, `TypeBounds(lo, hi) == TypeBounds(lo', hi')`
if `lo == lo'` and `hi == hi'`, if `hi = ObjectTpe` and `hi' = ObjectTpe'`,
`unique`'ing (hashconsing) such a `TypeBounds` would indirectly
replace `ObjectTpe` with `ObjectTpeJava` or vice versa.

We can't use `eq` when trying to identify `ObjectTpeJava` in `unique`
due to cycles.

`isAnyTpe` returns `true` for `ObjectTpeJava`.

Further fixes by Lukas:
  - Don't show ObjectTpeJava upper bound in TypeBounds.toString
  - Upper bounds of wildcards should be ObjectTpeJava
  - Fix wildcardExtrapolation for BoundedWildcardType with hi ObjectTpeJava

Reduce `_ >: lo <: ObjectTpeJava` to `lo`. This eliminates the
`BoundedWildcardType` in the expected type when type-checking the
lambda

    (c: java.util.Collection[String]).removeIf(x => true)

where

    boolean removeIf(Predicate<? super E> filter)

src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala

@@ -672,11 +672,11 @@ abstract class ClassfileParser(reader: ReusableInstance[ReusableDataReader]) {
                         case '+' => TypeBounds.upper(sig2type(tparams, skiptvs))
                         case '-' =>
                           val tp = sig2type(tparams, skiptvs)
-                          // sig2type seems to return AnyClass regardless of the situation:
-                          // we don't want Any as a LOWER bound.
-                          if (tp.typeSymbol == AnyClass) TypeBounds.empty
-                          else TypeBounds.lower(tp)
-                        case '*' => TypeBounds.empty
+                          // Interpret `sig2type` returning `Any` as "no bounds";
+                          // morally equivalent to TypeBounds.empty, but we're representing Java code, so use ObjectTpeJava for AnyTpe.
+                          if (tp.typeSymbol == AnyClass) TypeBounds.upper(definitions.ObjectTpeJava)
+                          else TypeBounds(tp, definitions.ObjectTpeJava)
+                        case '*' => TypeBounds.upper(definitions.ObjectTpeJava)
                       }
                       val newtparam = sym.newExistential(newTypeName("?"+i), sym.pos) setInfo bounds
                       existentials += newtparam

src/reflect/scala/reflect/internal/Definitions.scala

@@ -303,7 +303,7 @@ trait Definitions extends api.StandardDefinitions {
      *
      * We use `ObjectTpeJava`'s identity to equate it, but not `ObjectTpe`, to `AnyTpe` in subtyping and type equality.
      */
-    lazy val ObjectTpeJava   = mkObjectTpeJava
+    lazy val ObjectTpeJava   = new ObjectTpeJavaRef
 
     lazy val SerializableTpe = SerializableClass.tpe
     lazy val StringTpe       = StringClass.tpe

src/reflect/scala/reflect/internal/Types.scala

@@ -2409,7 +2409,11 @@ trait Types
       if (this eq other.asInstanceOf[AnyRef]) true
       else other match {
         case otherTypeRef: TypeRef =>
-          Objects.equals(pre, otherTypeRef.pre) && sym.eq(otherTypeRef.sym) && sameElementsEquals(args, otherTypeRef.args)
+          Objects.equals(pre, otherTypeRef.pre) &&
+            sym.eq(otherTypeRef.sym) &&
+            sameElementsEquals(args, otherTypeRef.args) &&
+            // `ObjectTpeJavaRef` is not structurally equal to `ObjectTpe` -- they should not be collapsed by `unique`
+            !(this.isInstanceOf[ObjectTpeJavaRef] || otherTypeRef.isInstanceOf[ObjectTpeJavaRef])
         case _ => false
       }
     }
@@ -2706,18 +2710,21 @@ trait Types
   private final class ClassArgsTypeRef(pre: Type, sym: Symbol, args: List[Type]) extends ArgsTypeRef(pre, sym, args)
   private final class AliasNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym) with AliasTypeRef
   private final class AbstractNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym) with AbstractTypeRef
-  private final class ClassNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym){
+  private final class ClassNoArgsTypeRef(pre: Type, sym: Symbol) extends NoArgsTypeRef(pre, sym) {
     override def contains(sym0: Symbol): Boolean = (sym eq sym0) || pre.contains(sym0)
   }
 
-  /** Expose ClassNoArgsTypeRef so we can create a non-uniqued ObjectTpeJava here and in reflect
-   *
-   * NOTE:
-   *   - definitions.ObjectTpe is forced first, so that it ends up in the unique cache.
-   *   - the created TypeRef is structurally equal to  ObjectTpe, but with its own identity
-   *   - we don't want the TypeRef we create here to be unique'd
-   */
-  private[scala] def mkObjectTpeJava: Type = new ClassNoArgsTypeRef(definitions.ObjectTpe.prefix, definitions.ObjectClass)
+  /** Expose ObjectTpeJavaRef so we can create a non-uniqued ObjectTpeJava
+    * (using a type test rather than `eq`, which causes cycles).
+    *
+    * NOTE:
+    *   - definitions.ObjectTpe is forced first, so that it ends up in the unique cache.
+    *   - the created TypeRef is structurally equal to ObjectTpe, but with its own identity
+    *   - we don't want the TypeRef we create here to be unique'd
+    */
+  private[internal] final class ObjectTpeJavaRef extends NoArgsTypeRef(definitions.ObjectTpe.prefix, definitions.ObjectClass) {
+    override def contains(sym0: Symbol): Boolean = (sym eq sym0) || pre.contains(sym0)
+  }
 
   object TypeRef extends TypeRefExtractor {
     def apply(pre: Type, sym: Symbol, args: List[Type]): Type = unique({
@@ -5207,7 +5214,7 @@ trait Types
     tp.dealias match {
       case PolyType(_, tp) => typeIsAny(tp)
       case TypeRef(_, AnyClass, _) => true
-      case _ => false
+      case _ => tp eq definitions.ObjectTpeJava
     }
 
   private[scala] val typeIsHigherKinded = (tp: Type) => tp.isHigherKinded

src/reflect/scala/reflect/internal/tpe/TypeMaps.scala

@@ -384,6 +384,7 @@ private[internal] trait TypeMaps {
     def apply(tp: Type): Type =
       tp match {
         case BoundedWildcardType(TypeBounds(lo, AnyTpe)) if variance.isContravariant => lo
+        case BoundedWildcardType(TypeBounds(lo, ObjectTpeJava)) if variance.isContravariant => lo
         case BoundedWildcardType(TypeBounds(NothingTpe, hi)) if variance.isCovariant => hi
         case tp => tp.mapOver(this)
       }

test/files/neg/abstract-class-error.check

@@ -1,6 +1,6 @@
 S.scala:1: error: class S needs to be abstract. Missing implementation for:
   def g(y: Int, z: java.util.List): Int // inherited from class J
-(Note that java.util.List does not match java.util.List[String]. To implement this raw type, use java.util.List[_ <: Object])
+(Note that java.util.List does not match java.util.List[String]. To implement this raw type, use java.util.List[_])
 class S extends J {
       ^
 one error found

test/files/neg/abstract-report2.check

@@ -11,7 +11,7 @@ Missing implementations for 13 members. Stub implementations follow:
   def removeAll(x$1: java.util.Collection[_]): Boolean = ???
   def retainAll(x$1: java.util.Collection[_]): Boolean = ???
   def size(): Int = ???
-  def toArray[T <: Object](x$1: Array[T with Object]): Array[T with Object] = ???
+  def toArray[T](x$1: Array[T with Object]): Array[T with Object] = ???
   def toArray(): Array[Object] = ???
 
 class Foo extends Collection[Int]
@@ -29,7 +29,7 @@ Missing implementations for 13 members. Stub implementations follow:
   def removeAll(x$1: java.util.Collection[_]): Boolean = ???
   def retainAll(x$1: java.util.Collection[_]): Boolean = ???
   def size(): Int = ???
-  def toArray[T <: Object](x$1: Array[T with Object]): Array[T with Object] = ???
+  def toArray[T](x$1: Array[T with Object]): Array[T with Object] = ???
   def toArray(): Array[Object] = ???
 
 class Bar extends Collection[List[_ <: String]]
@@ -47,7 +47,7 @@ Missing implementations for 13 members. Stub implementations follow:
   def removeAll(x$1: java.util.Collection[_]): Boolean = ???
   def retainAll(x$1: java.util.Collection[_]): Boolean = ???
   def size(): Int = ???
-  def toArray[T <: Object](x$1: Array[T with Object]): Array[T with Object] = ???
+  def toArray[T](x$1: Array[T with Object]): Array[T with Object] = ???
   def toArray(): Array[Object] = ???
 
 class Baz[T] extends Collection[T]

test/files/pos/t10418_unique.scala

@@ -0,0 +1,63 @@
+// scalac: -Ystop-after:refchecks -verbose -Ydebug -uniqid
+package java.lang
+
+/* This is a pretty random test that very indirectly tests `unique`ing of `ObjectTpeJavaRef`
+It's minimize from scala-js, where CI chanced on a compilation order that would first
+unique `TypeBounds(lo, ObjectTpe)`, and then `TypeBounds(lo, ObjectTpeJava)`,
+which would result in a Java reference to Object being replaced by one that is used
+to represent a Scala occurrence of a reference to Object, which is distinct from Any.
+When Java code refers to Object, it's taken as the same thing as Any, at least when
+it comes to =:= and `... <:< Object-in-java`.
+*/
+import java.util.Iterator
+
+class Class[A](o: Object)
+
+class Comparable[A] { def compareTo(o: A): scala.Int = ??? }
+
+object System {
+  def currentTimeMillis(): scala.Long = ???
+
+  def arraycopy(src: Object, srcPos: scala.Int, dest: Object, destPos: scala.Int, length: scala.Int): Unit = {
+    import scala.{Boolean, Double}
+
+    def mismatch(): Nothing =
+      throw new ArrayStoreException("Incompatible array types")
+
+    def copyPrim[@specialized T](src: Array[T], dest: Array[T]): Unit = {
+        var i = length-1
+        while (i >= 0) {
+          dest(i+destPos) = src(i+srcPos)
+          i -= 1
+        }
+    }
+
+    def copyRef(src: Array[AnyRef], dest: Array[AnyRef]): Unit = {
+      val x = (src.length, dest.length)
+
+      var i = length-1
+      while (i >= 0) {
+        dest(i+destPos) = src(i+srcPos)
+        i -= 1
+      }
+    }
+
+    (src match {
+      case src: Array[Boolean] =>
+        dest match {
+          case dest: Array[Boolean] => copyPrim(src, dest)
+          case _                    => mismatch()
+        }
+
+    })
+  }
+
+  def identityHashCode(x: Object): scala.Int = {
+    x.getClass
+    1
+  }
+}
+
+trait Iterable[T] {
+  def iterator():  java.util.Iterator[T]
+}

test/files/run/reflection-magicsymbols-invoke.check

@@ -7,7 +7,7 @@ method ##: ()Int
 method ==: (x$1: Any)Boolean
 method asInstanceOf: [T0]=> T0
 method equals: (x$1: Any)Boolean
-method getClass: ()Class[_ <: Object]
+method getClass: ()Class[_]
 method hashCode: ()Int
 method isInstanceOf: [T0]=> Boolean
 method toString: ()String
@@ -45,7 +45,7 @@ method clone: ()Object
 method eq: (x$1: AnyRef)Boolean
 method equals: (x$1: Object)Boolean
 method finalize: ()Unit
-method getClass: ()Class[_ <: Object]
+method getClass: ()Class[_]
 method hashCode: ()Int
 method isInstanceOf: [T0]=> Boolean
 method ne: (x$1: AnyRef)Boolean
@@ -91,7 +91,7 @@ method clone: ()Array[T]
 method eq: (x$1: AnyRef)Boolean
 method equals: (x$1: Object)Boolean
 method finalize: ()Unit
-method getClass: ()Class[_ <: Object]
+method getClass: ()Class[_]
 method hashCode: ()Int
 method isInstanceOf: [T0]=> Boolean
 method length: => Int

test/files/run/t5072.check

@@ -3,6 +3,6 @@ scala> class C
 defined class C
 
 scala> Thread.currentThread.getContextClassLoader.loadClass(classOf[C].getName)
-res0: Class[_ <: Object] = class C
+res0: Class[_] = class C
 
 scala> :quit