Support KClass.defaultType

compiler/testData/codegen/boxWithStdlib/reflection/classes/defaultType.kt

@@ -0,0 +1,25 @@
+import kotlin.reflect.defaultType
+import kotlin.reflect.jvm.javaType
+import kotlin.test.assertEquals
+import kotlin.test.assertNotEquals
+
+class Simple
+class Generic<K, V> {
+    fun thiz() = this
+}
+
+fun simple() = Simple()
+fun genericIntString() = Generic<Int, String>()
+
+fun box(): String {
+    assertEquals(javaClass<Simple>(), Simple::class.defaultType.javaType)
+    assertEquals(::simple.returnType, Simple::class.defaultType)
+
+    assertEquals(javaClass<Generic<*, *>>(), Generic::class.defaultType.javaType)
+    assertEquals(Generic<*, *>::thiz.returnType, Generic::class.defaultType)
+
+    // Generic<Int, String> != Generic<K, V>
+    assertNotEquals(::genericIntString.returnType, Generic::class.defaultType)
+
+    return "OK"
+}

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxWithStdlibCodegenTestGenerated.java

@@ -3012,6 +3012,12 @@ public class BlackBoxWithStdlibCodegenTestGenerated extends AbstractBlackBoxCode
                 doTestWithStdlib(fileName);
             }
 
+            @TestMetadata("defaultType.kt")
+            public void testDefaultType() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/reflection/classes/defaultType.kt");
+                doTestWithStdlib(fileName);
+            }
+
             @TestMetadata("jvmName.kt")
             public void testJvmName() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/reflection/classes/jvmName.kt");

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

@@ -19,6 +19,7 @@ package kotlin.reflect
 import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
 import kotlin.reflect.jvm.internal.KClassImpl
 import kotlin.reflect.jvm.internal.KFunctionImpl
+import kotlin.reflect.jvm.internal.KTypeImpl
 
 /**
  * Returns the primary constructor of this class, or `null` if this class has no primary constructor.
@@ -30,6 +31,14 @@ public val <T : Any> KClass<T>.primaryConstructor: KFunction<T>?
         ((it as KFunctionImpl).descriptor as ConstructorDescriptor).isPrimary
     }
 
+/**
+ * Returns a type corresponding to the given class with type parameters of that class substituted as the corresponding arguments.
+ * For example, for class `MyMap<K, V>` [defaultType] would return the type `MyMap<K, V>`.
+ */
+public val KClass<*>.defaultType: KType
+    get() = KTypeImpl((this as KClassImpl<*>).descriptor.defaultType) { jClass }
+
+
 /**
  * Returns static functions declared in this class.
  */