SI-8129 Make Object#== override Any#==

And the same for !=

If we tried to declare these signatures in non-fictional classes,
we would be chastised about collapsing into the "same signature after
erasure".

This will have an influence of typing, as the typechecking of
arguments is sensitive to overloading: if multiple variants are
feasible, the argument will be typechecked with a wildcard expected
type. So people inspecting the types of the arguments to `==` before
this change might have seen an interesting type for
`if (true) x else y`, but now the `If` will have type `Any`, as we
don't need to calculate the LUB.

I've left a TODO to note that we should really make `Any#{==, !=}`
non-final and include a final override in `AnyVal`. But I don't think
that is particularly urgent.

9 files changed, 16 insertions, 48 deletions

diff --git a/test/files/presentation/callcc-interpreter.check b/test/files/presentation/callcc-interpreter.check
index 1f868097ca..4bf68b3d4e 100644
--- a/test/files/presentation/callcc-interpreter.check
+++ b/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
diff --git a/test/files/presentation/completion-implicit-chained.check b/test/files/presentation/completion-implicit-chained.check
index f9d77f7a53..c583b7877c 100644
--- a/test/files/presentation/completion-implicit-chained.check
+++ b/test/files/presentation/completion-implicit-chained.check
@@ -3,7 +3,7 @@ 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
@@ -11,10 +11,8 @@ 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
diff --git a/test/files/presentation/ide-bug-1000349.check b/test/files/presentation/ide-bug-1000349.check
index c59fa6843f..79bfde5343 100644
--- a/test/files/presentation/ide-bug-1000349.check
+++ b/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
diff --git a/test/files/presentation/ide-bug-1000475.check b/test/files/presentation/ide-bug-1000475.check
index f5b4253e1a..4fb7f18285 100644
--- a/test/files/presentation/ide-bug-1000475.check
+++ b/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
diff --git a/test/files/presentation/ide-bug-1000531.check b/test/files/presentation/ide-bug-1000531.check
index dff89b155b..ef8a1d12de 100644
--- a/test/files/presentation/ide-bug-1000531.check
+++ b/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
diff --git a/test/files/presentation/implicit-member.check b/test/files/presentation/implicit-member.check
index 5ad52b4dd3..3bd3d8af41 100644
--- a/test/files/presentation/implicit-member.check
+++ b/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
diff --git a/test/files/presentation/ping-pong.check b/test/files/presentation/ping-pong.check
index 20f17aa7d0..ab4cfc9e7a 100644
--- a/test/files/presentation/ping-pong.check
+++ b/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
diff --git a/test/files/presentation/t5708.check b/test/files/presentation/t5708.check
index 04806b5867..4b33893e98 100644
--- a/test/files/presentation/t5708.check
+++ b/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
diff --git a/test/files/presentation/visibility.check b/test/files/presentation/visibility.check
index 217da34b9c..1ae1213f2d 100644
--- a/test/files/presentation/visibility.check
+++ b/test/files/presentation/visibility.check
@@ -3,7 +3,7 @@ reload: Completions.scala
 askTypeCompletion at Completions.scala(14,12)
 ================================================================================
 [response] askTypeCompletion at (14,12)
-retrieved 37 members
+retrieved 35 members
 [inaccessible] private[this] def secretPrivateThis(): Unit
 def +(other: String): String
 def ->[B](y: B): (accessibility.Foo, B)
@@ -19,10 +19,8 @@ def someTests(other: accessibility.Foo): Unit
 def toString(): String
 def →[B](y: B): (accessibility.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
@@ -43,7 +41,7 @@ protected[package lang] def finalize(): Unit
 askTypeCompletion at Completions.scala(16,11)
 ================================================================================
 [response] askTypeCompletion at (16,11)
-retrieved 37 members
+retrieved 35 members
 def +(other: String): String
 def ->[B](y: B): (accessibility.Foo, B)
 def ensuring(cond: Boolean): accessibility.Foo
@@ -58,10 +56,8 @@ def someTests(other: accessibility.Foo): Unit
 def toString(): String
 def →[B](y: B): (accessibility.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
@@ -83,7 +79,7 @@ protected[package lang] def finalize(): Unit
 askTypeCompletion at Completions.scala(22,11)
 ================================================================================
 [response] askTypeCompletion at (22,11)
-retrieved 37 members
+retrieved 35 members
 [inaccessible] private def secretPrivate(): Unit
 def +(other: String): String
 def ->[B](y: B): (accessibility.AccessibilityChecks, B)
@@ -100,10 +96,8 @@ def someTests: Unit
 def toString(): String
 def →[B](y: B): (accessibility.AccessibilityChecks, 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
@@ -123,7 +117,7 @@ protected[package lang] def finalize(): Unit
 askTypeCompletion at Completions.scala(28,10)
 ================================================================================
 [response] askTypeCompletion at (28,10)
-retrieved 37 members
+retrieved 35 members
 [inaccessible] private def secretPrivate(): Unit
 [inaccessible] private[this] def secretPrivateThis(): Unit
 [inaccessible] protected def secretProtected(): Unit
@@ -143,10 +137,8 @@ def someTests(other: accessibility.Foo): Unit
 def toString(): String
 def →[B](y: B): (accessibility.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
@@ -163,7 +155,7 @@ protected[package accessibility] def secretProtectedInPackage(): Unit
 askTypeCompletion at Completions.scala(37,8)
 ================================================================================
 [response] askTypeCompletion at (37,8)
-retrieved 37 members
+retrieved 35 members
 [inaccessible] private def secretPrivate(): Unit
 [inaccessible] private[this] def secretPrivateThis(): Unit
 [inaccessible] protected def secretProtected(): Unit
@@ -184,10 +176,8 @@ def someTests(other: accessibility.Foo): Unit
 def toString(): String
 def →[B](y: B): (accessibility.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