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/*
 * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
 * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
 */

package kotlin.reflect

/**
 * Represents a type. Type is usually either a class with optional type arguments,
 * or a type parameter of some declaration, plus nullability.
 */
public expect interface KType {
    /**
     * The declaration of the classifier used in this type.
     * For example, in the type `List` the classifier would be the [KClass] instance for [List].
     *
     * Returns `null` if this type is not denotable in Kotlin, for example if it is an intersection type.
     */
    @SinceKotlin("1.1")
    public val classifier: KClassifier?

    /**
     * Type arguments passed for the parameters of the classifier in this type.
     * For example, in the type `Array` 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.Inner` the returned list is `[C, D, A, B]`.
     */
    @SinceKotlin("1.1")
    public val arguments: List

    /**
     * `true` if this type was marked nullable in the source code.
     *
     * For Kotlin types, it means that `null` value is allowed to be represented by this type.
     * In practice it means that the type was declared with a question mark at the end.
     * For non-Kotlin types, it means the type or the symbol which was declared with this type
     * is annotated with a runtime-retained nullability annotation such as [javax.annotation.Nullable].
     *
     * Note that even if [isMarkedNullable] is false, values of the type can still be `null`.
     * This may happen if it is a type of the type parameter with a nullable upper bound:
     *
     * ```
     * fun  foo(t: T) {
     *     // isMarkedNullable == false for t's type, but t can be null here when T = "Any?"
     * }
     * ```
     */
    public val isMarkedNullable: Boolean
}