Nullability of intersection type should be determined by supertypes

Intersection types cannot be nullable as is because of special rules for subtyping

compiler/testData/codegen/box/regressions/noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt

@@ -0,0 +1,26 @@
+// !LANGUAGE: +NewInference
+
+class Recursive<T : Recursive<T>> : Generic<PlaceHolder<T>>, MainSupertype
+open class Simple<T> : Generic<T>, MainSupertype
+
+interface Generic<T>
+
+interface PlaceHolder<T : MainSupertype> : Stub<T>
+interface Stub<T : MainSupertype>
+
+interface MainSupertype
+
+interface SpecificStub<T : SpecificSimple> : Stub<T>
+abstract class SpecificSimple : Simple<SpecificStub<*>>()
+
+
+fun takeElement(recursive: Recursive<*>?, simpleWithSpecific: Simple<SpecificStub<*>>) {
+    select(recursive, simpleWithSpecific) // T -> intersection type
+}
+
+fun <T> select(x: T?, y: T): T = y
+
+fun box(): String {
+    takeElement(null, Simple())
+    return "OK"
+}

compiler/tests-ir-jvm/tests/org/jetbrains/kotlin/codegen/ir/IrBlackBoxCodegenTestGenerated.java

@@ -19432,6 +19432,12 @@ public class IrBlackBoxCodegenTestGenerated extends AbstractIrBlackBoxCodegenTes
             doTest(fileName);
         }
 
+        @TestMetadata("noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt")
+        public void testNoAssertionsWhenNullableTypeParameterReplacedWithIntersectionType() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("noCapturingForTypesWithTypeVariables.kt")
         public void testNoCapturingForTypesWithTypeVariables() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noCapturingForTypesWithTypeVariables.kt");

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -19432,6 +19432,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt")
+        public void testNoAssertionsWhenNullableTypeParameterReplacedWithIntersectionType() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("noCapturingForTypesWithTypeVariables.kt")
         public void testNoCapturingForTypesWithTypeVariables() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noCapturingForTypesWithTypeVariables.kt");

compiler/tests/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -19432,6 +19432,12 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
             doTest(fileName);
         }
 
+        @TestMetadata("noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt")
+        public void testNoAssertionsWhenNullableTypeParameterReplacedWithIntersectionType() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("noCapturingForTypesWithTypeVariables.kt")
         public void testNoCapturingForTypesWithTypeVariables() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noCapturingForTypesWithTypeVariables.kt");

core/descriptors/src/org/jetbrains/kotlin/types/TypeUtils.java

@@ -265,6 +265,14 @@ public class TypeUtils {
         if (isTypeParameter(type)) {
             return hasNullableSuperType(type);
         }
+
+        TypeConstructor constructor = type.getConstructor();
+        if (constructor instanceof IntersectionTypeConstructor) {
+            for (KotlinType supertype : constructor.getSupertypes()) {
+                if (isNullableType(supertype)) return true;
+            }
+        }
+
         return false;
     }
 

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/JsCodegenBoxTestGenerated.java

@@ -26423,6 +26423,12 @@ public class JsCodegenBoxTestGenerated extends AbstractJsCodegenBoxTest {
             throw new AssertionError("Looks like this test can be unmuted. Remove IGNORE_BACKEND directive or add it to whitelist for that.");
         }
 
+        @TestMetadata("noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt")
+        public void testNoAssertionsWhenNullableTypeParameterReplacedWithIntersectionType() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noAssertionsWhenNullableTypeParameterReplacedWithIntersectionType.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("noCapturingForTypesWithTypeVariables.kt")
         public void testNoCapturingForTypesWithTypeVariables() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/regressions/noCapturingForTypesWithTypeVariables.kt");