KT-4915 Smart completion should work for auto-casted 'this'

#KT-4915 Fixed

idea/idea-completion/testData/smart/smartCasts/SmartCastThisType.kt.todo

@@ -1,12 +0,0 @@
-open class Foo{
-    fun f() {
-        if (this is Bar){
-            var a : Bar = <caret>
-        }
-    }
-}
-
-class Bar : Foo
-
-
-// EXIST: { itemText:"this" }

idea/idea-completion/testData/smart/smartCasts/SmartCastThisType1.kt

@@ -0,0 +1,13 @@
+open class Foo{
+    fun Any.f() {
+        if (this@Foo is Bar && this is Bar){
+            var a: Bar = <caret>
+        }
+    }
+}
+
+class Bar : Foo
+
+
+// EXIST: { lookupString: "this" }
+// EXIST: { lookupString: "this@Foo" }

idea/idea-completion/testData/smart/smartCasts/SmartCastThisType2.kt

@@ -0,0 +1,16 @@
+open class Foo{
+    fun Bar.f() {
+        fun Any.g() {
+            if (this is Bar){
+                var a: Bar = this@<caret>
+            }
+        }
+    }
+}
+
+class Bar : Foo
+
+
+// EXIST: { lookupString: "this@g" }
+// EXIST: { lookupString: "this@f" }
+// ABSENT: { lookupString: "this@Foo" }