KT-5182 Data flow info is lost for 'when' branches

#KT-5158 Fixed
  #KT-4332 Fixed

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/kt4332WhenBranches.kt

@@ -0,0 +1,9 @@
+//KT-4332 when/autocast underperforms
+
+fun testWhen(t: String?, x: String?): Int {
+    return when {
+        t == null -> 0
+        x == null -> <!DEBUG_INFO_AUTOCAST!>t<!>.length // Wrong error report here. t can be inferred as not-null. (And it actually does if you replace when with if/else if)
+        else -> (<!DEBUG_INFO_AUTOCAST!>t<!> + x).length
+    }
+}