Proper implement 'classForImplicitThis'

compiler/testData/codegen/box/classes/inner/extensionWithOuter.kt

@@ -0,0 +1,12 @@
+class Outer(val value: String) {
+
+    inner class Inner {
+        fun Outer.foo() = value
+    }
+}
+
+fun Outer.Inner.test() = Outer("OK").foo()
+
+fun box(): String {
+    return Outer("Fail").Inner().test()
+}