Annotation Declarations and Uses

AnnotationDeclaration = Visibility? "annotation" Identifier
                        ImplementsClause? AggregateBody ;
AnnotationUse         = "@" Identifier ("(" AnnotationArgumentList? ")")? ;
AnnotationArgumentList = Expression ("," NamedArgument)* | NamedArgumentList ;

Annotation bodies share field, constructor, and method syntax with class bodies. Interfaces following implements declare targets and retention policy; see the annotation specification for the complete set of standard interfaces.

Annotations may precede packages, enums, interfaces, classes, values, annotations, fields, constructors, functions, methods, parameters, and local variables. Application arguments accept compile-time metadata values. The first argument may omit its label when the annotation declaration has a value parameter: @Get("/{name}") equals @Get(value: "/{name}"). All other arguments must be named.