Merge pull request scala#3497 from adriaanm/rebase-3464

 Make Object#== override Any#==

src/compiler/scala/tools/nsc/typechecker/Infer.scala

@@ -174,7 +174,8 @@ trait Infer extends Checkable {
   private lazy val stdErrorValue = stdErrorClass.newErrorValue(nme.ERROR)
 
   /** The context-dependent inferencer part */
-  class Inferencer(context: Context) extends InferencerContextErrors with InferCheckable {
+  abstract class Inferencer extends InferencerContextErrors with InferCheckable {
+    def context: Context
     import InferErrorGen._
 
     /* -- Error Messages --------------------------------------------------- */

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -109,7 +109,8 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
 
     private val transformed: mutable.Map[Tree, Tree] = unit.transformed
 
-    val infer = new Inferencer(context0) {
+    val infer = new Inferencer {
+      def context = Typer.this.context
       // See SI-3281 re undoLog
       override def isCoercible(tp: Type, pt: Type) = undoLog undo viewExists(tp, pt)
     }

src/library-aux/scala/AnyRef.scala

@@ -76,8 +76,8 @@ trait AnyRef extends Any {
    *  @param    arg0  the object to compare against this object for equality.
    *  @return         `true` if the receiver object is equivalent to the argument; `false` otherwise.
    */
-  final def ==(that: AnyRef): Boolean =
-    if (this eq null) that eq null
+  final def ==(that: Any): Boolean =
+    if (this eq null) that.asInstanceOf[AnyRef] eq null
     else this equals that
 
   /** Create a copy of the receiver object.

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

@@ -35,7 +35,8 @@ trait Definitions extends api.StandardDefinitions {
   private def newMethod(owner: Symbol, name: TermName, formals: List[Type], restpe: Type, flags: Long): MethodSymbol = {
     val msym   = owner.newMethod(name.encode, NoPosition, flags)
     val params = msym.newSyntheticValueParams(formals)
-    msym setInfo MethodType(params, restpe) markAllCompleted
+    val info = if (owner.isJavaDefined) JavaMethodType(params, restpe) else MethodType(params, restpe)
+    msym setInfo info markAllCompleted
   }
   private def enterNewMethod(owner: Symbol, name: TermName, formals: List[Type], restpe: Type, flags: Long = 0L): MethodSymbol =
     owner.info.decls enter newMethod(owner, name, formals, restpe, flags)
@@ -904,8 +905,14 @@ trait Definitions extends api.StandardDefinitions {
       existentialAbstraction(clazz.unsafeTypeParams, clazz.tpe_*)
 
     // members of class scala.Any
+
+    // TODO these aren't final! They are now overriden in AnyRef/Object. Prior to the fix
+    //      for SI-8129, they were actually *overloaded* by the members in AnyRef/Object.
+    //      We should unfinalize these, override in AnyValClass, and make the overrides final.
+    //      Refchecks never actually looks at these, so its just for consistency.
     lazy val Any_==       = enterNewMethod(AnyClass, nme.EQ, AnyTpe :: Nil, BooleanTpe, FINAL)
     lazy val Any_!=       = enterNewMethod(AnyClass, nme.NE, AnyTpe :: Nil, BooleanTpe, FINAL)
+
     lazy val Any_equals   = enterNewMethod(AnyClass, nme.equals_, AnyTpe :: Nil, BooleanTpe)
     lazy val Any_hashCode = enterNewMethod(AnyClass, nme.hashCode_, Nil, IntTpe)
     lazy val Any_toString = enterNewMethod(AnyClass, nme.toString_, Nil, StringTpe)
@@ -1012,8 +1019,8 @@ trait Definitions extends api.StandardDefinitions {
 
     // members of class java.lang.{ Object, String }
     lazy val Object_## = enterNewMethod(ObjectClass, nme.HASHHASH, Nil, IntTpe, FINAL)
-    lazy val Object_== = enterNewMethod(ObjectClass, nme.EQ, AnyRefTpe :: Nil, BooleanTpe, FINAL)
-    lazy val Object_!= = enterNewMethod(ObjectClass, nme.NE, AnyRefTpe :: Nil, BooleanTpe, FINAL)
+    lazy val Object_== = enterNewMethod(ObjectClass, nme.EQ, AnyTpe :: Nil, BooleanTpe, FINAL)
+    lazy val Object_!= = enterNewMethod(ObjectClass, nme.NE, AnyTpe :: Nil, BooleanTpe, FINAL)
     lazy val Object_eq = enterNewMethod(ObjectClass, nme.eq, AnyRefTpe :: Nil, BooleanTpe, FINAL)
     lazy val Object_ne = enterNewMethod(ObjectClass, nme.ne, AnyRefTpe :: Nil, BooleanTpe, FINAL)
     lazy val Object_isInstanceOf = newT1NoParamsMethod(ObjectClass, nme.isInstanceOf_Ob, FINAL | SYNTHETIC | ARTIFACT)(_ => BooleanTpe)

test/files/neg/t8219-any-any-ref-equals.check

@@ -0,0 +1,10 @@
+t8219-any-any-ref-equals.scala:5: error: method ==: (x$1: Any)Boolean does not take type parameters.
+  "".==[Int]
+       ^
+t8219-any-any-ref-equals.scala:6: error: method ==: (x$1: Any)Boolean does not take type parameters.
+  ("": AnyRef).==[Int]
+                 ^
+t8219-any-any-ref-equals.scala:7: error: method ==: (x$1: Any)Boolean does not take type parameters.
+  ("": Object).==[Int]
+                 ^
+three errors found

test/files/neg/t8219-any-any-ref-equals.scala

@@ -0,0 +1,8 @@
+object Test {
+  // The error message tells us that AnyRef#== and Any#== are overloaded.
+  // A real class couldn't define such an overload, why do we allow AnyRef
+  // to do so?
+  "".==[Int]
+  ("": AnyRef).==[Int]
+  ("": Object).==[Int]
+}

test/files/pos/t8219.scala

@@ -0,0 +1,15 @@
+trait Equalizer[T]
+trait Gen[A]
+
+class Broken {
+  implicit def const[T](x: T): Gen[T] = ???
+  implicit def convertToEqualizer[T](left: T): Equalizer[T] = ???
+
+  def in(a: Any) = ()
+  in {
+    import scala.None // any import will do..
+    "" == "" // this no longer triggers the bug, as Object#== now overrides Any#==
+  }
+
+  // We can still trigger the bug with a structural type, see pending/neg/t8219.scala
+}

test/files/pos/t8219b.scala

@@ -0,0 +1,49 @@
+trait Equalizer[T]
+trait Gen[A]
+
+class Broken {
+  implicit def const[T](x: T): Gen[T] = ???
+  implicit def convertToEqualizer[T](left: T): Equalizer[T] = ???
+
+  def in(a: Any) = ()
+  in {
+    import scala.None // any import will do..
+    "" == "" // no longer a problem, see pos/t8129.scala
+  }
+
+  // We used to fall into the errant code path above when `Any#==` and `AnyRef#==`
+  // were overloaded.
+  //
+  // Real classes couldn't get away with that overloading; it would result in
+  // a compiler error because the variants would collapse into an overriding
+  // relationship after erasure.
+  //
+  //
+  // But, a structural type can! This triggers the same error, and served as
+  // a backstop for this test if we change the signatures of `AnyRef#==` to
+  // override `Any#==`.
+  type T = {
+    def a(a: AnyRef): Boolean
+    def a(a: Any): Boolean
+  }
+
+  def t: T = ???
+
+  in {
+    import scala.None // any import will do..
+    t.a("")
+  }
+
+  // Or, we can get here with ambiguous implicits from the formal parameter
+  // type of the less specific overload to that of the more specific.
+  object T {
+    def foo(a: Any) = true
+    def foo(a: String) = true
+  }
+  in {
+    import scala.None
+    implicit def any2str1(a: Any) = ""
+    implicit def any2str2(a: Any) = ""
+    T.foo("")
+  }
+}

test/files/presentation/callcc-interpreter.check

@@ -3,7 +3,7 @@ reload: CallccInterpreter.scala
 askTypeCompletion at CallccInterpreter.scala(51,34)
 ================================================================================
 [response] askTypeCompletion at (51,34)
-retrieved 59 members
+retrieved 57 members
 abstract trait Term extends AnyRef
 abstract trait Value extends AnyRef
 case class Add extends callccInterpreter.Term with Product with Serializable
@@ -38,10 +38,8 @@ def toString(): String
 def unitM[A](a: A): callccInterpreter.M[A]
 def →[B](y: B): (callccInterpreter.type, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean

test/files/presentation/completion-implicit-chained.check

@@ -3,18 +3,16 @@ reload: Completions.scala
 askTypeCompletion at Completions.scala(11,16)
 ================================================================================
 [response] askTypeCompletion at (11,16)
-retrieved 24 members
+retrieved 22 members
 [inaccessible] protected[package lang] def clone(): Object
 [inaccessible] protected[package lang] def finalize(): Unit
 def equals(x$1: Any): Boolean
 def hashCode(): Int
 def map(x: Int => Int)(implicit a: DummyImplicit): test.O.type
 def toString(): String
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean

test/files/presentation/ide-bug-1000349.check

@@ -3,7 +3,7 @@ reload: CompletionOnEmptyArgMethod.scala
 askTypeCompletion at CompletionOnEmptyArgMethod.scala(2,17)
 ================================================================================
 [response] askTypeCompletion at (2,17)
-retrieved 32 members
+retrieved 30 members
 def +(other: String): String
 def ->[B](y: B): (Foo, B)
 def ensuring(cond: Boolean): Foo
@@ -17,10 +17,8 @@ def hashCode(): Int
 def toString(): String
 def →[B](y: B): (Foo, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean

test/files/presentation/ide-bug-1000475.check

@@ -3,7 +3,7 @@ reload: Foo.scala
 askTypeCompletion at Foo.scala(3,7)
 ================================================================================
 [response] askTypeCompletion at (3,7)
-retrieved 31 members
+retrieved 29 members
 [inaccessible] protected[package lang] def clone(): Object
 [inaccessible] protected[package lang] def finalize(): Unit
 def +(other: String): String
@@ -18,10 +18,8 @@ def hashCode(): Int
 def toString(): String
 def →[B](y: B): (Object, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean
@@ -37,7 +35,7 @@ final def wait(x$1: Long,x$2: Int): Unit
 askTypeCompletion at Foo.scala(6,10)
 ================================================================================
 [response] askTypeCompletion at (6,10)
-retrieved 31 members
+retrieved 29 members
 [inaccessible] protected[package lang] def clone(): Object
 [inaccessible] protected[package lang] def finalize(): Unit
 def +(other: String): String
@@ -52,10 +50,8 @@ def hashCode(): Int
 def toString(): String
 def →[B](y: B): (Object, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean
@@ -71,7 +67,7 @@ final def wait(x$1: Long,x$2: Int): Unit
 askTypeCompletion at Foo.scala(7,7)
 ================================================================================
 [response] askTypeCompletion at (7,7)
-retrieved 31 members
+retrieved 29 members
 [inaccessible] protected[package lang] def clone(): Object
 [inaccessible] protected[package lang] def finalize(): Unit
 def +(other: String): String
@@ -86,10 +82,8 @@ def hashCode(): Int
 def toString(): String
 def →[B](y: B): (Object, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean

test/files/presentation/ide-bug-1000531.check

@@ -3,7 +3,7 @@ reload: CrashOnLoad.scala
 askTypeCompletion at CrashOnLoad.scala(6,12)
 ================================================================================
 [response] askTypeCompletion at (6,12)
-retrieved 120 members
+retrieved 118 members
 [inaccessible] protected[package lang] def clone(): Object
 [inaccessible] protected[package lang] def finalize(): Unit
 [inaccessible] protected[this] def reversed: List[B]
@@ -107,10 +107,8 @@ def zipWithIndex: Iterator[(B, Int)]
 def zip[B](that: Iterator[B]): Iterator[(B, B)]
 def →[B](y: B): (java.util.Iterator[B], B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean

test/files/presentation/implicit-member.check

@@ -3,7 +3,7 @@ reload: ImplicitMember.scala
 askTypeCompletion at ImplicitMember.scala(7,7)
 ================================================================================
 [response] askTypeCompletion at (7,7)
-retrieved 34 members
+retrieved 32 members
 def +(other: String): String
 def ->[B](y: B): (Implicit.type, B)
 def ensuring(cond: Boolean): Implicit.type
@@ -17,10 +17,8 @@ def toString(): String
 def →[B](y: B): (Implicit.type, B)
 final class AppliedImplicit[A] extends AnyRef
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean

test/files/presentation/ping-pong.check

@@ -3,7 +3,7 @@ reload: PingPong.scala
 askTypeCompletion at PingPong.scala(10,23)
 ================================================================================
 [response] askTypeCompletion at (10,23)
-retrieved 35 members
+retrieved 33 members
 [inaccessible] private[this] val ping: Ping
 [inaccessible] protected[package lang] def clone(): Object
 [inaccessible] protected[package lang] def finalize(): Unit
@@ -19,10 +19,8 @@ def hashCode(): Int
 def poke(): Unit
 def →[B](y: B): (Pong, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean
@@ -40,7 +38,7 @@ private[this] val name: String
 askTypeCompletion at PingPong.scala(19,20)
 ================================================================================
 [response] askTypeCompletion at (19,20)
-retrieved 35 members
+retrieved 33 members
 [inaccessible] protected[package lang] def clone(): Object
 [inaccessible] protected[package lang] def finalize(): Unit
 def +(other: String): String
@@ -57,10 +55,8 @@ def name: String
 def poke: Unit
 def →[B](y: B): (Ping, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean

test/files/presentation/t5708.check

@@ -3,7 +3,7 @@ reload: Completions.scala
 askTypeCompletion at Completions.scala(17,9)
 ================================================================================
 [response] askTypeCompletion at (17,9)
-retrieved 39 members
+retrieved 37 members
 [inaccessible] private def privateM: String
 [inaccessible] private[this] val privateV: String
 [inaccessible] private[this] val protectedV: String
@@ -22,10 +22,8 @@ def hashCode(): Int
 def toString(): String
 def →[B](y: B): (test.Compat.type, B)
 final def !=(x$1: Any): Boolean
-final def !=(x$1: AnyRef): Boolean
 final def ##(): Int
 final def ==(x$1: Any): Boolean
-final def ==(x$1: AnyRef): Boolean
 final def asInstanceOf[T0]: T0
 final def eq(x$1: AnyRef): Boolean
 final def isInstanceOf[T0]: Boolean