[NI] Add feature for choosing candidate by lambda return type

core/util.runtime/src/org/jetbrains/kotlin/utils/addToStdlib.kt

@@ -148,4 +148,17 @@ inline fun <T, R, C : MutableCollection<in R>> Iterable<T>.flatMapToNullable(des
 }
 
 fun <E : Enum<E>> min(a: E, b: E): E = if (a < b) a else b
-fun <E : Comparable<E>> min(a: E, b: E): E = if (a < b) a else b
+fun <E : Comparable<E>> min(a: E, b: E): E = if (a < b) a else b
+
+inline fun <T, R> Iterable<T>.same(extractor: (T) -> R): Boolean {
+    val iterator = iterator()
+    val firstValue = extractor(iterator.next())
+    while (iterator.hasNext()) {
+        val item = iterator.next()
+        val value = extractor(item)
+        if (value != firstValue) {
+            return false
+        }
+    }
+    return true
+}