[NI] Fix not-null smartcast on intersection of nullable types

#KT-28670 Fixed

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

@@ -142,7 +142,7 @@ internal class DataFlowInfoImpl private constructor(
 
     private fun KotlinType.canBeDefinitelyNotNullOrNotNull(settings: LanguageVersionSettings): Boolean {
         return if (settings.supportsFeature(LanguageFeature.NewInference))
-            this.isMarkedNullable || DefinitelyNotNullType.makesSenseToBeDefinitelyNotNull(this.unwrap())
+            TypeUtils.isNullableType(this)
         else
             this.isMarkedNullable
     }

compiler/testData/diagnostics/tests/generics/nullability/notNullSmartcastOnIntersectionOfNullables.kt

@@ -0,0 +1,18 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+interface A
+interface B {
+    fun test() {}
+}
+
+fun <K> select(a: K, b: K): K = a
+
+fun test(a: A?, b: B?) {
+    b as A?
+    a as B?
+    val c = select(a, b)
+    if (c != null) {
+        <!DEBUG_INFO_SMARTCAST!>c<!>.test()
+    }
+}

compiler/testData/diagnostics/tests/generics/nullability/notNullSmartcastOnIntersectionOfNullables.txt

@@ -0,0 +1,17 @@
+package
+
+public fun </*0*/ K> select(/*0*/ a: K, /*1*/ b: K): K
+public fun test(/*0*/ a: A?, /*1*/ b: B?): kotlin.Unit
+
+public interface A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun test(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -8435,6 +8435,11 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     runTest("compiler/testData/diagnostics/tests/generics/nullability/kt25182.kt");
                 }
 
+                @TestMetadata("notNullSmartcastOnIntersectionOfNullables.kt")
+                public void testNotNullSmartcastOnIntersectionOfNullables() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/generics/nullability/notNullSmartcastOnIntersectionOfNullables.kt");
+                }
+
                 @TestMetadata("nullToGeneric.kt")
                 public void testNullToGeneric() throws Exception {
                     runTest("compiler/testData/diagnostics/tests/generics/nullability/nullToGeneric.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -8435,6 +8435,11 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                     runTest("compiler/testData/diagnostics/tests/generics/nullability/kt25182.kt");
                 }
 
+                @TestMetadata("notNullSmartcastOnIntersectionOfNullables.kt")
+                public void testNotNullSmartcastOnIntersectionOfNullables() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/generics/nullability/notNullSmartcastOnIntersectionOfNullables.kt");
+                }
+
                 @TestMetadata("nullToGeneric.kt")
                 public void testNullToGeneric() throws Exception {
                     runTest("compiler/testData/diagnostics/tests/generics/nullability/nullToGeneric.kt");

core/descriptors/src/org/jetbrains/kotlin/types/SpecialTypes.kt

@@ -81,8 +81,8 @@ class DefinitelyNotNullType private constructor(val original: SimpleType) : Dele
             }
         }
 
-        fun makesSenseToBeDefinitelyNotNull(type: UnwrappedType): Boolean =
-                type.canHaveUndefinedNullability() && !NullabilityChecker.isSubtypeOfAny(type)
+        private fun makesSenseToBeDefinitelyNotNull(type: UnwrappedType): Boolean =
+            type.canHaveUndefinedNullability() && !NullabilityChecker.isSubtypeOfAny(type)
     }
 
     override val delegate: SimpleType