Call chains: receiver data flow info is dropped for extensions with nullable receiver #KT-10056 Fixed

compiler/testData/diagnostics/tests/smartCasts/safecalls/nullableReceiver.kt

@@ -0,0 +1,15 @@
+// See KT-10056
+class Foo(val bar: String)
+
+public inline fun <T, R> T.let(f: (T) -> R): R = f(this)
+
+fun test(foo: Foo?) {
+    foo?.bar.let {
+        // Error, foo?.bar is nullable
+        it<!UNSAFE_CALL!>.<!>length
+        // Error, foo is nullable
+        foo<!UNSAFE_CALL!>.<!>bar.length
+        // Correct
+        foo?.bar?.length
+    }
+}