Java 8 rules for method overrides:

- report errors on implementing methods of Any in interfaces
- update testData

~~~

Java 8 override restrictions: interface can't implement a method of 'Any'
- update compiler sources

compiler/testData/codegen/box/classes/kt285.kt

@@ -1,12 +1,15 @@
 interface Trait {
     fun foo() = "O"
-    override fun toString() = "K"
+    fun bar(): String
 }
 
-class SimpleClass : Trait
+class SimpleClass : Trait {
+    override fun bar() = "K"
+}
 
+// Delegating 'toString' doesn't work, see KT-9519
 class ComplexClass : Trait by SimpleClass() {
-    override fun toString() = foo() + super.toString()
+    fun qux() = foo() + bar()
 }
 
-fun box() = ComplexClass().toString()
+fun box() = ComplexClass().qux()

compiler/testData/codegen/box/super/unqualifiedSuperWithMethodsOfAny.kt

@@ -8,10 +8,6 @@ interface IWithToString {
     override fun toString(): String
 }
 
-interface IWithDefaultToString {
-    override fun toString(): String = "I"
-}
-
 class C1 : ClassWithToString(), ISomething {
     override fun toString(): String = super.toString()
 }
@@ -20,15 +16,10 @@ class C2 : ClassWithToString(), IWithToString, ISomething  {
     override fun toString(): String = super.toString()
 }
 
-class C3 : IWithDefaultToString, ISomething  {
-    override fun toString(): String = super.toString()
-}
-
 fun box(): String {
     return when {
         C1().toString() != "C" -> "Failed #1"
         C2().toString() != "C" -> "Failed #2"
-        C3().toString() != "I" -> "Failed #3"
         else -> "OK"
     }
 }

compiler/testData/codegen/box/traits/kt5393_toString.kt

@@ -1,15 +0,0 @@
-interface A {
-    override fun toString(): String {
-        return "OK"
-    }
-}
-
-interface B : A
-
-class C : B {
-    override fun toString(): String {
-        return super.toString()
-    }
-}
-
-fun box() = "${C()}"