Extract Function: Implement duplicate search

idea/testData/refactoring/extractFunction/duplicates/singleExpression.kt.after

@@ -0,0 +1,29 @@
+// PARAM_TYPES: kotlin.Int
+// PARAM_TYPES: kotlin.Int
+// PARAM_DESCRIPTOR: value-parameter val a: kotlin.Int defined in foo
+// PARAM_DESCRIPTOR: value-parameter val b: kotlin.Int defined in foo
+
+// SIBLING:
+fun foo(a: Int, b: Int): Int {
+    return i(a, b) + 1
+}
+
+private fun i(a: Int, b: Int): Int {
+    return a + b * a
+}
+
+fun bar() {
+    fun f() = 1
+
+    val a = 1
+    val b = 2
+    val c = 3
+
+    i(c, b)
+    i(b, a)
+    i(a, a)
+    a + a*b
+    a + c
+    i(f(), a)
+    i(f(), f())
+}