Extract Function: Implement duplicate search

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

@@ -0,0 +1,25 @@
+// 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 <selection>a + b*a</selection> + 1
+}
+
+fun bar() {
+    fun f() = 1
+
+    val a = 1
+    val b = 2
+    val c = 3
+
+    c + b*c
+    b + a*b
+    a plus a*a
+    a + a*b
+    a + c
+    f() + a*f()
+    f() + f().times(f())
+}