> ## Documentation Index > Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt > Use this file to discover all available pages before exploring further. # Kotlin Target Annotation The `@Target` meta-annotation in Kotlin dictates the specific syntactic elements to which a custom annotation can be applied. By applying `@Target` to an annotation class declaration, the compiler enforces structural constraints, preventing the annotation from being attached to invalid language constructs during compilation. It accepts a `vararg` of `kotlin.annotation.AnnotationTarget` enum values. ```kotlin theme={"dark"} @Target( AnnotationTarget.CLASS, AnnotationTarget.FUNCTION, AnnotationTarget.VALUE_PARAMETER ) annotation class RestrictedAnnotation ``` ## The `AnnotationTarget` Enum The `AnnotationTarget` enum provides granular control over Kotlin's language features, which often map to multiple underlying JVM elements. The available targets include: * **`CLASS`**: Classes, interfaces, objects, and annotation classes. * **`ANNOTATION_CLASS`**: Restricted exclusively to other annotation classes (used for defining meta-annotations). * **`TYPE_PARAMETER`**: Generic type parameter declarations (e.g., ``). * **`PROPERTY`**: Kotlin properties. * **`FIELD`**: Backing fields of properties. * **`LOCAL_VARIABLE`**: Variables declared within a function or block scope. * **`VALUE_PARAMETER`**: Parameters of functions or constructors. * **`CONSTRUCTOR`**: Primary or secondary constructors. * **`FUNCTION`**: Functions (excluding constructors). * **`PROPERTY_GETTER` / `PROPERTY_SETTER`**: Explicit or implicit property accessors. * **`TYPE`**: Type usages (e.g., the type specified in a variable declaration, function return type, or supertype). * **`EXPRESSION`**: Arbitrary expressions. * **`FILE`**: File-level declarations. * **`TYPEALIAS`**: Typealias declarations. ## Default Behavior If the `@Target` meta-annotation is omitted from an annotation class declaration, the Kotlin compiler applies a default set of targets. The annotation implicitly becomes applicable to: `CLASS`, `PROPERTY`, `FIELD`, `LOCAL_VARIABLE`, `VALUE_PARAMETER`, `CONSTRUCTOR`, `FUNCTION`, `PROPERTY_GETTER`, and `PROPERTY_SETTER`. It implicitly excludes `TYPE`, `TYPE_PARAMETER`, `EXPRESSION`, `FILE`, and `TYPEALIAS` (note that `ANNOTATION_CLASS` is technically covered by the inclusion of `CLASS`). ## Resolution and Use-Site Targets Because a primary constructor parameter declared with `val` or `var` simultaneously declares a property, it can generate multiple underlying JVM elements (the constructor parameter, a backing field, a getter, and a setter). The `@Target` annotation dictates how the compiler resolves ambiguous applications in these overlapping constructs. If an annotation's `@Target` includes both `PROPERTY` and `FIELD`, applying it to a property declaration defaults to the `PROPERTY` target. To force the annotation onto the backing field or an accessor, the developer must use use-site target syntax, provided those targets are explicitly permitted by the annotation's `@Target` declaration. ```kotlin theme={"dark"} @Target(AnnotationTarget.PROPERTY, AnnotationTarget.FIELD) annotation class DualTargetAnnotation class Example { // Resolves to AnnotationTarget.PROPERTY based on default compiler resolution @DualTargetAnnotation val defaultTarget: String = "" // Explicitly resolves to AnnotationTarget.FIELD using use-site syntax @field:DualTargetAnnotation val explicitTarget: String = "" } ```

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