pkg/meta/lib/meta.dart - sdk.git - Git at Google

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 /// Constants for use in metadata annotations.
 ///
 /// See also `@deprecated` and `@override` in the `dart:core` library.
 ///
 /// Annotations provide semantic information that tools can use to provide a
 /// better user experience. For example, an IDE might not autocomplete the name
 /// of a function that's been marked `@deprecated`, or it might display the
 /// function's name differently.
 ///
 /// For information on installing and importing this library, see the
 /// [meta package on pub.dartlang.org] (http://pub.dartlang.org/packages/meta).
 /// For examples of using annotations, see
 /// [Metadata](https://www.dartlang.org/docs/dart-up-and-running/ch02.html#metadata)
 /// in the language tour.
 library meta;

 /// Used to annotate a function `f`. Indicates that `f` always throws an
 /// exception. Any functions that override `f`, in class inheritence, are also
 /// expected to conform to this contract.
 ///
 /// Tools, such as the analyzer, can use this to understand whether a block of
 /// code "exits". For example:
 ///
 /// ```dart
 /// @alwaysThrows toss() { throw 'Thrown'; }
 ///
 /// int fn(bool b) {
 ///   if (b) {
 ///     return 0;
 ///   } else {
 ///     toss();
 ///     print("Hello.");
 ///   }
 /// }
 /// ```
 ///
 /// Without the annotation on `toss`, it would look as though `fn` doesn't
 /// always return a value. The annotation shows that `fn` does always exit. In
 /// addition, the annotation reveals that any statements following a call to
 /// `toss` (like the `print` call) are dead code.
 ///
 /// Tools, such as the analyzer, can also expect this contract to be enforced;
 /// that is, tools may emit warnings if a function with this annotation
 /// _doesn't_ always throw.
 const _AlwaysThrows alwaysThrows = const _AlwaysThrows();

 /// Used to annotate a parameter of an instance method that overrides another
 /// method.
 ///
 /// Indicates that this parameter may have a tighter type than the parameter on
 /// its superclass. The actual argument will be checked at runtime to ensure it
 /// is a subtype of the overridden parameter type.
 ///
 /// DEPRECATED: Use the `covariant` modifier instead.
 @deprecated
 const _Checked checked = const _Checked();

 /// Used to annotate a library, or any declaration that is part of the public
 /// interface of a library (such as top-level members, class members, and
 /// function parameters) to indicate that the annotated API is experimental and
 /// may be removed or changed at any-time without updating the version of the
 /// containing package, despite the fact that it would otherwise be a breaking
 /// change.
 ///
 /// If the annotation is applied to a library then it is equivalent to applying
 /// the annotation to all of the top-level members of the library. Applying the
 /// annotation to a class does *not* apply the annotation to subclasses, but
 /// does apply the annotation to members of the class.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with a declaration that is not part of the
 ///   public interface of a library (such as a local variable or a declaration
 ///   that is private) or a directive other than the first directive in the
 ///   library, or
 /// * the declaration is referenced by a package that has not explicitly
 ///   indicated its intention to use experimental APIs (details TBD).
 const _Experimental experimental = const _Experimental();

 /// Used to annotate an instance or static method `m`. Indicates that `m` must
 /// either be abstract or must return a newly allocated object or `null`. In
 /// addition, every method that either implements or overrides `m` is implicitly
 /// annotated with this same annotation.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with anything other than a method, or
 /// * the annotation is associated with a method that has this annotation that
 ///   can return anything other than a newly allocated object or `null`.
 const _Factory factory = const _Factory();

 /// Used to annotate a class `C`. Indicates that `C` and all subtypes of `C`
 /// must be immutable.
 ///
 /// A class is immutable if all of the instance fields of the class, whether
 /// defined directly or inherited, are `final`.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 /// * the annotation is associated with anything other than a class, or
 /// * a class that has this annotation or extends, implements or mixes in a
 ///   class that has this annotation is not immutable.
 const Immutable immutable = const Immutable();

 /// Used to annotate a const constructor `c`. Indicates that any invocation of
 /// the constructor must use the keyword `const` unless one or more of the
 /// arguments to the constructor is not a compile-time constant.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with anything other than a const constructor,
 ///   or
 /// * an invocation of a constructor that has this annotation is not invoked
 ///   using the `const` keyword unless one or more of the arguments to the
 ///   constructor is not a compile-time constant.
 const _Literal literal = const _Literal();

 /// Used to annotate an instance method `m`. Indicates that every invocation of
 /// a method that overrides `m` must also invoke `m`. In addition, every method
 /// that overrides `m` is implicitly annotated with this same annotation.
 ///
 /// Note that private methods with this annotation cannot be validly overridden
 /// outside of the library that defines the annotated method.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with anything other than an instance method,
 ///   or
 /// * a method that overrides a method that has this annotation can return
 ///   without invoking the overridden method.
 const _MustCallSuper mustCallSuper = const _MustCallSuper();

 /// Used to annotate a class declaration `C`. Indicates that any type arguments
 /// declared on `C` are to be treated as optional.  Tools such as the analyzer
 /// and linter can use this information to suppress warnings that would
 /// otherwise require type arguments to be provided for instances of `C`.
 const _OptionalTypeArgs optionalTypeArgs = const _OptionalTypeArgs();

 /// Used to annotate an instance member (method, getter, setter, operator, or
 /// field) `m` in a class `C`. If the annotation is on a field it applies to the
 /// getter, and setter if appropriate, that are induced by the field. Indicates
 /// that `m` should only be invoked from instance methods of `C` or classes that
 /// extend, implement or mix in `C`, either directly or indirectly. Additionally
 /// indicates that `m` should only be invoked on `this`, whether explicitly or
 /// implicitly.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with anything other than an instance member,
 ///   or
 /// * an invocation of a member that has this annotation is used outside of an
 ///   instance member defined on a class that extends or mixes in the class in
 ///   which the protected member is defined, or that uses a receiver other than
 ///   `this`.
 const _Protected protected = const _Protected();

 /// Used to annotate a named parameter `p` in a method or function `f`.
 /// Indicates that every invocation of `f` must include an argument
 /// corresponding to `p`, despite the fact that `p` would otherwise be an
 /// optional parameter.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with anything other than a named parameter,
 /// * the annotation is associated with a named parameter in a method `m1` that
 ///   overrides a method `m0` and `m0` defines a named parameter with the same
 ///   name that does not have this annotation, or
 /// * an invocation of a method or function does not include an argument
 ///   corresponding to a named parameter that has this annotation.
 const Required required = const Required();

 /// Used to annotate a field that is allowed to be overridden in Strong Mode.
 const _Virtual virtual = const _Virtual();

 /// Used to annotate an instance member that was made public so that it could be
 /// overridden but that is not intended to be referenced from outside the
 /// defining library.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with a declaration other than a public
 ///   instance member in a class, or
 /// * the member is referenced outside of the defining library.
 const _VisibleForOverriding visibleForOverriding =
     const _VisibleForOverriding();

 /// Used to annotate a declaration was made public, so that it is more visible
 /// than otherwise necessary, to make code testable.
 ///
 /// Tools, such as the analyzer, can provide feedback if
 ///
 /// * the annotation is associated with a declaration not in the `lib` folder
 ///   of a package, or
 /// * the declaration is referenced outside of its the defining library or a
 ///   library which is in the `test` folder of the defining package.
 const _VisibleForTesting visibleForTesting = const _VisibleForTesting();

 /// Used to annotate a class.
 ///
 /// See [immutable] for more details.
 class Immutable {
   /// A human-readable explanation of the reason why the class is immutable.
   final String reason;

   /// Initialize a newly created instance to have the given [reason].
   const Immutable([this.reason]);
 }

 /// Used to annotate a named parameter `p` in a method or function `f`.
 ///
 /// See [required] for more details.
 class Required {
   /// A human-readable explanation of the reason why the annotated parameter is
   /// required. For example, the annotation might look like:
   ///
   ///     ButtonWidget({
   ///         Function onHover,
   ///         @Required('Buttons must do something when pressed')
   ///         Function onPressed,
   ///         ...
   ///     }) ...
   final String reason;

   /// Initialize a newly created instance to have the given [reason].
   const Required([this.reason]);
 }

 class _AlwaysThrows {
   const _AlwaysThrows();
 }

 class _Checked {
   const _Checked();
 }

 class _Experimental {
   const _Experimental();
 }

 class _Factory {
   const _Factory();
 }

 class _Literal {
   const _Literal();
 }

 class _MustCallSuper {
   const _MustCallSuper();
 }

 class _OptionalTypeArgs {
   const _OptionalTypeArgs();
 }

 class _Protected {
   const _Protected();
 }

 class _Virtual {
   const _Virtual();
 }

 class _VisibleForOverriding {
   const _VisibleForOverriding();
 }

 class _VisibleForTesting {
   const _VisibleForTesting();
 }
	// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	/// Constants for use in metadata annotations.
	///
	/// See also `@deprecated` and `@override` in the `dart:core` library.
	///
	/// Annotations provide semantic information that tools can use to provide a
	/// better user experience. For example, an IDE might not autocomplete the name
	/// of a function that's been marked `@deprecated`, or it might display the
	/// function's name differently.
	///
	/// For information on installing and importing this library, see the
	/// [meta package on pub.dartlang.org] (http://pub.dartlang.org/packages/meta).
	/// For examples of using annotations, see
	/// [Metadata](https://www.dartlang.org/docs/dart-up-and-running/ch02.html#metadata)
	/// in the language tour.
	library meta;

	/// Used to annotate a function `f`. Indicates that `f` always throws an
	/// exception. Any functions that override `f`, in class inheritence, are also
	/// expected to conform to this contract.
	///
	/// Tools, such as the analyzer, can use this to understand whether a block of
	/// code "exits". For example:
	///
	/// ```dart
	/// @alwaysThrows toss() { throw 'Thrown'; }
	///
	/// int fn(bool b) {
	/// if (b) {
	/// return 0;
	/// } else {
	/// toss();
	/// print("Hello.");
	/// }
	/// }
	/// ```
	///
	/// Without the annotation on `toss`, it would look as though `fn` doesn't
	/// always return a value. The annotation shows that `fn` does always exit. In
	/// addition, the annotation reveals that any statements following a call to
	/// `toss` (like the `print` call) are dead code.
	///
	/// Tools, such as the analyzer, can also expect this contract to be enforced;
	/// that is, tools may emit warnings if a function with this annotation
	/// _doesn't_ always throw.
	const _AlwaysThrows alwaysThrows = const _AlwaysThrows();

	/// Used to annotate a parameter of an instance method that overrides another
	/// method.
	///
	/// Indicates that this parameter may have a tighter type than the parameter on
	/// its superclass. The actual argument will be checked at runtime to ensure it
	/// is a subtype of the overridden parameter type.
	///
	/// DEPRECATED: Use the `covariant` modifier instead.
	@deprecated
	const _Checked checked = const _Checked();

	/// Used to annotate a library, or any declaration that is part of the public
	/// interface of a library (such as top-level members, class members, and
	/// function parameters) to indicate that the annotated API is experimental and
	/// may be removed or changed at any-time without updating the version of the
	/// containing package, despite the fact that it would otherwise be a breaking
	/// change.
	///
	/// If the annotation is applied to a library then it is equivalent to applying
	/// the annotation to all of the top-level members of the library. Applying the
	/// annotation to a class does not apply the annotation to subclasses, but
	/// does apply the annotation to members of the class.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with a declaration that is not part of the
	/// public interface of a library (such as a local variable or a declaration
	/// that is private) or a directive other than the first directive in the
	/// library, or
	/// * the declaration is referenced by a package that has not explicitly
	/// indicated its intention to use experimental APIs (details TBD).
	const _Experimental experimental = const _Experimental();

	/// Used to annotate an instance or static method `m`. Indicates that `m` must
	/// either be abstract or must return a newly allocated object or `null`. In
	/// addition, every method that either implements or overrides `m` is implicitly
	/// annotated with this same annotation.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with anything other than a method, or
	/// * the annotation is associated with a method that has this annotation that
	/// can return anything other than a newly allocated object or `null`.
	const _Factory factory = const _Factory();

	/// Used to annotate a class `C`. Indicates that `C` and all subtypes of `C`
	/// must be immutable.
	///
	/// A class is immutable if all of the instance fields of the class, whether
	/// defined directly or inherited, are `final`.
	///
	/// Tools, such as the analyzer, can provide feedback if
	/// * the annotation is associated with anything other than a class, or
	/// * a class that has this annotation or extends, implements or mixes in a
	/// class that has this annotation is not immutable.
	const Immutable immutable = const Immutable();

	/// Used to annotate a const constructor `c`. Indicates that any invocation of
	/// the constructor must use the keyword `const` unless one or more of the
	/// arguments to the constructor is not a compile-time constant.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with anything other than a const constructor,
	/// or
	/// * an invocation of a constructor that has this annotation is not invoked
	/// using the `const` keyword unless one or more of the arguments to the
	/// constructor is not a compile-time constant.
	const _Literal literal = const _Literal();

	/// Used to annotate an instance method `m`. Indicates that every invocation of
	/// a method that overrides `m` must also invoke `m`. In addition, every method
	/// that overrides `m` is implicitly annotated with this same annotation.
	///
	/// Note that private methods with this annotation cannot be validly overridden
	/// outside of the library that defines the annotated method.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with anything other than an instance method,
	/// or
	/// * a method that overrides a method that has this annotation can return
	/// without invoking the overridden method.
	const _MustCallSuper mustCallSuper = const _MustCallSuper();

	/// Used to annotate a class declaration `C`. Indicates that any type arguments
	/// declared on `C` are to be treated as optional. Tools such as the analyzer
	/// and linter can use this information to suppress warnings that would
	/// otherwise require type arguments to be provided for instances of `C`.
	const _OptionalTypeArgs optionalTypeArgs = const _OptionalTypeArgs();

	/// Used to annotate an instance member (method, getter, setter, operator, or
	/// field) `m` in a class `C`. If the annotation is on a field it applies to the
	/// getter, and setter if appropriate, that are induced by the field. Indicates
	/// that `m` should only be invoked from instance methods of `C` or classes that
	/// extend, implement or mix in `C`, either directly or indirectly. Additionally
	/// indicates that `m` should only be invoked on `this`, whether explicitly or
	/// implicitly.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with anything other than an instance member,
	/// or
	/// * an invocation of a member that has this annotation is used outside of an
	/// instance member defined on a class that extends or mixes in the class in
	/// which the protected member is defined, or that uses a receiver other than
	/// `this`.
	const _Protected protected = const _Protected();

	/// Used to annotate a named parameter `p` in a method or function `f`.
	/// Indicates that every invocation of `f` must include an argument
	/// corresponding to `p`, despite the fact that `p` would otherwise be an
	/// optional parameter.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with anything other than a named parameter,
	/// * the annotation is associated with a named parameter in a method `m1` that
	/// overrides a method `m0` and `m0` defines a named parameter with the same
	/// name that does not have this annotation, or
	/// * an invocation of a method or function does not include an argument
	/// corresponding to a named parameter that has this annotation.
	const Required required = const Required();

	/// Used to annotate a field that is allowed to be overridden in Strong Mode.
	const _Virtual virtual = const _Virtual();

	/// Used to annotate an instance member that was made public so that it could be
	/// overridden but that is not intended to be referenced from outside the
	/// defining library.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with a declaration other than a public
	/// instance member in a class, or
	/// * the member is referenced outside of the defining library.
	const _VisibleForOverriding visibleForOverriding =
	const _VisibleForOverriding();

	/// Used to annotate a declaration was made public, so that it is more visible
	/// than otherwise necessary, to make code testable.
	///
	/// Tools, such as the analyzer, can provide feedback if
	///
	/// * the annotation is associated with a declaration not in the `lib` folder
	/// of a package, or
	/// * the declaration is referenced outside of its the defining library or a
	/// library which is in the `test` folder of the defining package.
	const _VisibleForTesting visibleForTesting = const _VisibleForTesting();

	/// Used to annotate a class.
	///
	/// See [immutable] for more details.
	class Immutable {
	/// A human-readable explanation of the reason why the class is immutable.
	final String reason;

	/// Initialize a newly created instance to have the given [reason].
	const Immutable([this.reason]);
	}

	/// Used to annotate a named parameter `p` in a method or function `f`.
	///
	/// See [required] for more details.
	class Required {
	/// A human-readable explanation of the reason why the annotated parameter is
	/// required. For example, the annotation might look like:
	///
	/// ButtonWidget({
	/// Function onHover,
	/// @Required('Buttons must do something when pressed')
	/// Function onPressed,
	/// ...
	/// }) ...
	final String reason;

	/// Initialize a newly created instance to have the given [reason].
	const Required([this.reason]);
	}

	class _AlwaysThrows {
	const _AlwaysThrows();
	}

	class _Checked {
	const _Checked();
	}

	class _Experimental {
	const _Experimental();
	}

	class _Factory {
	const _Factory();
	}

	class _Literal {
	const _Literal();
	}

	class _MustCallSuper {
	const _MustCallSuper();
	}

	class _OptionalTypeArgs {
	const _OptionalTypeArgs();
	}

	class _Protected {
	const _Protected();
	}

	class _Virtual {
	const _Virtual();
	}

	class _VisibleForOverriding {
	const _VisibleForOverriding();
	}

	class _VisibleForTesting {
	const _VisibleForTesting();
	}