Support smart casts to Type after x as? Type null check #KT-4565 Fixed

compiler/testData/diagnostics/tests/smartCasts/castchecks/insideCall.kt

@@ -0,0 +1,13 @@
+// !LANGUAGE: +SafeCastCheckBoundSmartCasts
+// See KT-19007
+
+// Stub
+fun String.indexOf(arg: String) = this.length - arg.length
+
+// Stub
+fun String.toLowerCase() = this
+
+fun foo(a: Any) {
+    // Should compile in 1.2
+    (a as? String)?.indexOf(<!DEBUG_INFO_SMARTCAST!>a<!>.toLowerCase())
+}