Reflection: add KType.withNullability

compiler/testData/codegen/box/reflection/mapping/types/withNullability.kt

@@ -0,0 +1,20 @@
+// WITH_REFLECT
+
+import kotlin.reflect.withNullability
+import kotlin.reflect.jvm.javaType
+import kotlin.test.assertEquals
+
+fun nonNull(): String = ""
+fun nullable(): String? = ""
+
+fun box(): String {
+    val nonNull = ::nonNull.returnType
+    val nullable = ::nullable.returnType
+
+    assertEquals(nullable.javaType, nullable.withNullability(false).javaType)
+    assertEquals(nullable.javaType, nullable.withNullability(true).javaType)
+    assertEquals(nonNull.javaType, nonNull.withNullability(false).javaType)
+    assertEquals(nullable.javaType, nonNull.withNullability(true).javaType)
+
+    return "OK"
+}

compiler/testData/codegen/box/reflection/types/withNullability.kt

@@ -0,0 +1,30 @@
+// WITH_REFLECT
+// FILE: J.java
+
+public interface J {
+    String platform();
+}
+
+// FILE: K.kt
+
+import kotlin.reflect.withNullability
+import kotlin.test.assertEquals
+
+fun nonNull(): String = ""
+fun nullable(): String? = ""
+
+fun box(): String {
+    val nonNull = ::nonNull.returnType
+    val nullable = ::nullable.returnType
+    val platform = J::platform.returnType
+
+    assertEquals(nonNull, nullable.withNullability(false))
+    assertEquals(nullable, nullable.withNullability(true))
+    assertEquals(nonNull, nonNull.withNullability(false))
+    assertEquals(nullable, nonNull.withNullability(true))
+
+    assertEquals(nonNull, platform.withNullability(false))
+    assertEquals(nullable, platform.withNullability(true))
+
+    return "OK"
+}

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

@@ -12490,6 +12490,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/mapping/types/unit.kt");
                     doTest(fileName);
                 }
+
+                @TestMetadata("withNullability.kt")
+                public void testWithNullability() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/mapping/types/withNullability.kt");
+                    doTest(fileName);
+                }
             }
         }
 
@@ -13056,6 +13062,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("withNullability.kt")
+            public void testWithNullability() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/types/withNullability.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("compiler/testData/codegen/box/reflection/types/createType")
             @TestDataPath("$PROJECT_ROOT")
             @RunWith(JUnit3RunnerWithInners.class)

core/reflection.jvm/src/kotlin/reflect/KTypes.kt

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2010-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+@file:JvmName("KTypes")
+package kotlin.reflect
+
+import org.jetbrains.kotlin.types.TypeUtils
+import org.jetbrains.kotlin.types.isFlexible
+import kotlin.reflect.jvm.internal.KTypeImpl
+
+/**
+ * Returns a new type with the same classifier, arguments and annotations as the given type, and with the given nullability.
+ */
+fun KType.withNullability(nullable: Boolean): KType {
+    if (isMarkedNullable) {
+        return if (nullable) this else KTypeImpl(TypeUtils.makeNotNullable((this as KTypeImpl).type)) { javaType }
+    }
+
+    // If the type is not marked nullable, it's either a non-null type or a platform type.
+    val kotlinType = (this as KTypeImpl).type
+    if (kotlinType.isFlexible()) return KTypeImpl(TypeUtils.makeNullableAsSpecified(kotlinType, nullable)) { javaType }
+
+    return if (!nullable) this else KTypeImpl(TypeUtils.makeNullable(kotlinType)) { javaType }
+}