KT-2819 Duplicate toString() method generated in data class

#KT-2819 Fixed

compiler/testData/codegen/dataClasses/equals/alreadyDeclared.kt

@@ -0,0 +1,8 @@
+data class A(val x: Int) {
+  fun equals(other: Any?): Boolean = false
+}
+
+fun box(): String {
+  val a = A(0)
+  return if (a equals a) "fail" else "OK"
+}

compiler/testData/codegen/dataClasses/equals/alreadyDeclaredWrongSignature.kt

@@ -0,0 +1,38 @@
+data class A(val x: Int) {
+  fun equals(other: Any): Boolean = false
+}
+
+data class B(val x: Int) {
+  fun equals(other: B): Boolean = false
+}
+
+data class C(val x: Int) {
+  fun equals(): Boolean = false
+}
+
+data class D(val x: Int) {
+  fun equals(other: Any?, another: String): Boolean = false
+}
+
+data class E(val x: Int) {
+  fun equals(x: E): Boolean = false
+  fun equals(x: Any?): Boolean = false
+}
+
+fun box(): String {
+  javaClass<A>().getDeclaredMethod("equals", javaClass<Any>())
+
+  javaClass<B>().getDeclaredMethod("equals", javaClass<Any>())
+  javaClass<B>().getDeclaredMethod("equals", javaClass<B>())
+
+  javaClass<C>().getDeclaredMethod("equals", javaClass<Any>())
+  javaClass<C>().getDeclaredMethod("equals")
+
+  javaClass<D>().getDeclaredMethod("equals", javaClass<Any>())
+  javaClass<D>().getDeclaredMethod("equals", javaClass<Any>(), javaClass<String>())
+
+  javaClass<E>().getDeclaredMethod("equals", javaClass<Any>())
+  javaClass<E>().getDeclaredMethod("equals", javaClass<E>())
+
+  return "OK"
+}