Deduct x != null from x?.y is NotNullType

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/DelegatingDataFlowInfo.kt

@@ -231,9 +231,13 @@ internal class DelegatingDataFlowInfo private constructor(
         if (value.type == type) return this
         if (getCollectedTypes(value).contains(type)) return this
         if (!value.type.isFlexible() && value.type.isSubtypeOf(type)) return this
-        val newNullabilityInfo = if (type.isMarkedNullable) EMPTY_NULLABILITY_INFO else ImmutableMap.of(value, NOT_NULL)
         val newTypeInfo = newTypeInfo()
         newTypeInfo.put(value, type)
+        val builder = Maps.newHashMap<DataFlowValue, Nullability>()
+        if (!type.isMarkedNullable) {
+            putNullability(builder, value, NOT_NULL)
+        }
+        val newNullabilityInfo = if (type.isMarkedNullable) EMPTY_NULLABILITY_INFO else ImmutableMap.copyOf(builder)
         return create(this, newNullabilityInfo, newTypeInfo)
     }
 

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

@@ -52,8 +52,7 @@ fun kt4565_1(a: SomeClass?) {
         <!DEBUG_INFO_SMARTCAST!>a<!>.data.hashCode()
     }
     if (a?.data is String) {
-        // To be supported
-        a<!UNSAFE_CALL!>.<!>data.<!UNRESOLVED_REFERENCE!>length<!>
+        <!DEBUG_INFO_SMARTCAST!>a<!>.data.<!UNRESOLVED_REFERENCE!>length<!>
         data.<!UNRESOLVED_REFERENCE!>length<!>
     }
 }