Reflection: change order of arguments of inner generic type

As in KClassifier.createType and everywhere in the compiler, specify arguments
for the innermost type first. This is more convenient to use because generally
the construction/introspection of such type starts from the innermost class
anyway (i.e. something like generateSequence can be used, without the need to
call .reverse() in the end)

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

@@ -0,0 +1,28 @@
+// WITH_REFLECT
+
+import kotlin.reflect.jvm.javaType
+import kotlin.test.assertEquals
+
+class Outer<A, B> {
+    inner class Inner<C, D> {
+        inner class Innermost<E, F>
+    }
+}
+
+fun foo(): Outer<Int, Number>.Inner<String, Float>.Innermost<Any, Any?> = null!!
+
+fun box(): String {
+    assertEquals(
+            listOf(
+                    Any::class.java,
+                    Any::class.java,
+                    String::class.java,
+                    Float::class.javaObjectType,
+                    Int::class.javaObjectType,
+                    Number::class.java
+            ),
+            ::foo.returnType.arguments.map { it.type!!.javaType }
+    )
+
+    return "OK"
+}

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

@@ -0,0 +1,32 @@
+// WITH_REFLECT
+
+import kotlin.test.*
+
+class Outer<A, B> {
+    inner class Inner<C, D> {
+        inner class Innermost<E, F>
+    }
+}
+
+fun foo(): Outer<Int, Number>.Inner<String, Float>.Innermost<Any, Any?> = null!!
+
+fun box(): String {
+    val types = ::foo.returnType.arguments.map { it.type!! }
+
+    assertEquals(
+            listOf(
+                    Any::class,
+                    Any::class,
+                    String::class,
+                    Float::class,
+                    Int::class,
+                    Number::class
+            ),
+            types.map { it.classifier }
+    )
+
+    assertFalse(types[0].isMarkedNullable)
+    assertTrue(types[1].isMarkedNullable)
+
+    return "OK"
+}

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

@@ -12464,6 +12464,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("innerGenericTypeArgument.kt")
+                public void testInnerGenericTypeArgument() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/mapping/types/innerGenericTypeArgument.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("memberFunctions.kt")
                 public void testMemberFunctions() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/mapping/types/memberFunctions.kt");
@@ -13173,6 +13179,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("innerGenericArguments.kt")
+            public void testInnerGenericArguments() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/types/innerGenericArguments.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("jvmErasureOfClass.kt")
             public void testJvmErasureOfClass() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/reflection/types/jvmErasureOfClass.kt");

core/builtins/src/kotlin/reflect/KType.kt

@@ -32,6 +32,10 @@ public interface KType {
     /**
      * Type arguments passed for the parameters of the classifier in this type.
      * For example, in the type `Array<out Number>` the only type argument is `out Number`.
+     *
+     * In case this type is based on an inner class, the returned list contains the type arguments provided for the innermost class first,
+     * then its outer class, and so on.
+     * For example, in the type `Outer<A, B>.Inner<C, D>` the returned list is `[C, D, A, B]`.
      */
     public val arguments: List<KTypeProjection>
 

core/descriptors.runtime/src/org/jetbrains/kotlin/load/java/structure/reflect/ReflectJavaClassifierType.kt

@@ -47,9 +47,7 @@ class ReflectJavaClassifierType(public override val reflectType: Type) : Reflect
         get() = with(reflectType) { this is Class<*> && getTypeParameters().isNotEmpty() }
 
     override val typeArguments: List<JavaType>
-        get() = generateSequence({ reflectType as? ParameterizedType }, { it.ownerType as? ParameterizedType }).flatMap {
-            it.actualTypeArguments.asSequence().map { ReflectJavaType.create(it) }
-        }.toList()
+        get() = reflectType.parameterizedTypeArguments.map(ReflectJavaType.Factory::create)
 
     override val annotations: Collection<JavaAnnotation>
         get() {

core/descriptors.runtime/src/org/jetbrains/kotlin/load/java/structure/reflect/reflectClassUtil.kt

@@ -20,6 +20,8 @@ import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import java.lang.reflect.Array
+import java.lang.reflect.ParameterizedType
+import java.lang.reflect.Type
 
 val Class<*>.safeClassLoader: ClassLoader
     get() = classLoader ?: ClassLoader.getSystemClassLoader()
@@ -74,3 +76,16 @@ val Class<*>.desc: String
 
 fun Class<*>.createArrayType(): Class<*> =
         Array.newInstance(this, 0).javaClass
+
+/**
+ * @return all arguments of a parameterized type, including those of outer classes in case this type represents an inner generic.
+ * The returned list starts with the arguments to the innermost class, then continues with those of its outer class, and so on.
+ * For example, for the type `Outer<A, B>.Inner<C, D>` the result would be `[C, D, A, B]`.
+ */
+val Type.parameterizedTypeArguments: List<Type>
+    get() {
+        if (this !is ParameterizedType) return emptyList()
+        if (ownerType == null) return actualTypeArguments.toList()
+
+        return generateSequence(this) { it.ownerType as? ParameterizedType }.flatMap { it.actualTypeArguments.asSequence() }.toList()
+    }

core/reflection.jvm/src/kotlin/reflect/jvm/internal/KTypeImpl.kt

@@ -20,6 +20,7 @@ import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.TypeAliasDescriptor
 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.load.java.structure.reflect.createArrayType
+import org.jetbrains.kotlin.load.java.structure.reflect.parameterizedTypeArguments
 import org.jetbrains.kotlin.load.java.structure.reflect.primitiveByWrapper
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeUtils
@@ -75,12 +76,7 @@ internal class KTypeImpl(
             val typeArguments = type.arguments
             if (typeArguments.isEmpty()) return emptyList()
 
-            // Lazy because it's not needed to compute javaType right away, only inside the lazy value for each argument,
-            // and also because sometimes (e.g. in case of star projections), this won't be needed at all.
-            // Note that this instance is created before the loop because ParameterizedType#actualTypeArguments clones the array
-            val javaTypeArguments by lazy(PUBLICATION) {
-                (javaType as ParameterizedType).actualTypeArguments
-            }
+            val parameterizedTypeArguments by lazy(PUBLICATION) { javaType.parameterizedTypeArguments }
 
             return typeArguments.mapIndexed { i, typeProjection ->
                 if (typeProjection.isStarProjection) {
@@ -100,7 +96,7 @@ internal class KTypeImpl(
                                 javaType.genericComponentType
                             }
                             is ParameterizedType -> {
-                                val argument = javaTypeArguments[i]
+                                val argument = parameterizedTypeArguments[i]
                                 // In "Foo<out Bar>", the JVM type of the first type argument should be "Bar", not "? extends Bar"
                                 if (argument !is WildcardType) argument
                                 else argument.lowerBounds.firstOrNull() ?: argument.upperBounds.first()