From 896f874b9f6dab2ce1485d1caa2aa5ab89d05445 Mon Sep 17 00:00:00 2001
From: Brian Wilkerson <brianwilkerson@google.com>
Date: Fri, 17 Jul 2020 19:01:17 +0000
Subject: [PATCH] An initial definition of the Target annotation

Change-Id: I6980da1e869c57b15a8bd068fef17f33d6a884ab
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154380
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Nate Bosch <nbosch@google.com>
Reviewed-by: Phil Quitslund <pquitslund@google.com>
---
 pkg/meta/lib/meta_meta.dart                   | 83 +++++++++++++++++++
 .../expectation.txt                           |  1 +
 .../loader/valid_packages/expectation.txt     |  1 +
 3 files changed, 85 insertions(+)
 create mode 100644 pkg/meta/lib/meta_meta.dart

diff --git a/pkg/meta/lib/meta_meta.dart b/pkg/meta/lib/meta_meta.dart
new file mode 100644
index 00000000000..5090b051df2
--- /dev/null
+++ b/pkg/meta/lib/meta_meta.dart
@@ -0,0 +1,83 @@
+// Copyright (c) 2020, 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.
+
+/// Annotations that describe the intended use of other annotations.
+library meta_meta;
+
+/// An annotation used on classes that are intended to be used as annotations
+/// to indicate the kinds of declarations and directives for which the
+/// annotation is appropriate.
+///
+/// The kinds are represented by the constants defined in [TargetKind].
+///
+/// Tools, such as the analyzer, can provide feedback if
+///
+/// * the annotation is associated with anything other than a class, where the
+///   class must be usable as an annotation (that is, contain at least one
+///   `const` constructor).
+/// * the annotated annotation is associated with anything other than the kinds
+///   of declarations listed as valid targets.
+@Target({TargetKind.classType})
+class Target {
+  /// The kinds of declarations with which the annotated annotation can be
+  /// associated.
+  final Set<TargetKind> kinds;
+
+  const Target(this.kinds);
+}
+
+/// An enumeration of the kinds of targets to which an annotation can be
+/// applied.
+enum TargetKind {
+  /// Indicates that an annotation is valid on any class declaration.
+  classType,
+
+  /// Indicates that an annotation is valid on any enum declaration.
+  enumType,
+
+  /// Indicates that an annotation is valid on any extension declaration.
+  extension,
+
+  /// Indicates that an annotation is valid on any field declaration, both
+  /// instance and static fields, whether it's in a class, mixin or extension.
+  field,
+
+  /// Indicates that an annotation is valid on any top-level function
+  /// declaration.
+  function,
+
+  /// Indicates that an annotation is valid on the first directive in a library,
+  /// whether that's a `library`, `import`, `export` or `part` directive. This
+  /// doesn't include the `part of` directive in a part file.
+  library,
+
+  /// Indicates that an annotation is valid on any getter declaration, both
+  /// instance or static getters, whether it's in a class, mixin, extension, or
+  /// at the top-level of a library.
+  getter,
+
+  /// Indicates that an annotation is valid on any method declaration, both
+  /// instance and static methods, whether it's in a class, mixin or extension.
+  method,
+
+  /// Indicates that an annotation is valid on any mixin declaration.
+  mixinType,
+
+  /// Indicates that an annotation is valid on any formal parameter declaration,
+  /// whether it's in a function, method, constructor, or closure.
+  parameter,
+
+  /// Indicates that an annotation is valid on any setter declaration, both
+  /// instance or static setters, whether it's in a class, mixin, extension, or
+  /// at the top-level of a library.
+  setter,
+
+  /// Indicates that an annotation is valid on any declaration that introduces a
+  /// type. This includes classes, enums, mixins and typedefs, but does not
+  /// include extensions because extensions don't introduce a type.
+  type,
+
+  /// Indicates that an annotation is valid on any typedef declaration.
+  typedefType,
+}
diff --git a/pkg/modular_test/test/loader/default_package_dependency_error/expectation.txt b/pkg/modular_test/test/loader/default_package_dependency_error/expectation.txt
index 05c60439b04..e00a4e24211 100644
--- a/pkg/modular_test/test/loader/default_package_dependency_error/expectation.txt
+++ b/pkg/modular_test/test/loader/default_package_dependency_error/expectation.txt
@@ -23,6 +23,7 @@ meta
   dependencies: sdk
   lib/dart2js.dart
   lib/meta.dart
+  lib/meta_meta.dart
 
 sdk
   is package? no
diff --git a/pkg/modular_test/test/loader/valid_packages/expectation.txt b/pkg/modular_test/test/loader/valid_packages/expectation.txt
index 680cfc57126..e3bfaeb225b 100644
--- a/pkg/modular_test/test/loader/valid_packages/expectation.txt
+++ b/pkg/modular_test/test/loader/valid_packages/expectation.txt
@@ -32,6 +32,7 @@ meta
   dependencies: sdk
   lib/dart2js.dart
   lib/meta.dart
+  lib/meta_meta.dart
 
 sdk
   is package? no