Reflection: add utilities to filter parameters by kind and name

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

@@ -0,0 +1,45 @@
+/*
+ * 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("KCallables")
+package kotlin.reflect
+
+/**
+ * Returns a parameter representing the `this` instance needed to call this callable,
+ * or `null` if this callable is not a member of a class and thus doesn't take such parameter.
+ */
+val KCallable<*>.instanceParameter: KParameter?
+    get() = parameters.singleOrNull { it.kind == KParameter.Kind.INSTANCE }
+
+/**
+ * Returns a parameter representing the extension receiver instance needed to call this callable,
+ * or `null` if this callable is not an extension.
+ */
+val KCallable<*>.extensionReceiverParameter: KParameter?
+    get() = parameters.singleOrNull { it.kind == KParameter.Kind.EXTENSION_RECEIVER }
+
+/**
+ * Returns parameters of this callable, excluding the `this` instance and the extension receiver parameter.
+ */
+val KCallable<*>.valueParameters: List<KParameter>
+    get() = parameters.filter { it.kind == KParameter.Kind.VALUE }
+
+/**
+ * Returns the parameter of this callable with the given name, or `null` if there's no such parameter.
+ */
+fun KCallable<*>.findParameterByName(name: String): KParameter? {
+    return parameters.singleOrNull { it.name == name }
+}