[FIR] Implement FUNCTION_EXPECTED

compiler/testData/diagnostics/tests/smartCasts/variables/whileTrue.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 fun x(): Boolean { return true }
 
 public fun foo(pp: Any): Int {
@@ -11,4 +10,4 @@ public fun foo(pp: Any): Int {
     // Smart cast is NOT possible here
     // (we could provide it but p = 42 makes it difficult to understand)
     return p.<!UNRESOLVED_REFERENCE!>length<!>()
-}
+}