Deprecate provisional and Provisional and make them unusable.

Will be removed in Dart 3.

Change-Id: I0bf8b01f23bab5a7871f0562562b7ad98887394f
Reviewed-on: https://dart-review.googlesource.com/69462
Reviewed-by: Leaf Petersen <leafp@google.com>
Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>

CHANGELOG.md

@@ -14,6 +14,11 @@
 
 ### Core library changes
 
+#### `dart:core`:
+*   Deprecated the `provisional` annotation and the `Provisional`
+    annotation class. These should have been removed before releasing Dart 2.0,
+    and they have no effect.
+
 ## 2.1.0-dev.1.0
 
 ### Tool Changes

sdk/lib/cli/wait_for.dart

@@ -111,7 +111,6 @@ class _WaitForUtils {
  * subsequent calls block waiting for a condition that is only satisfied when
  * an earlier call returns.
  */
-@provisional
 T waitFor<T>(Future<T> future, {Duration timeout}) {
   T result;
   bool futureCompleted = false;

sdk/lib/core/annotations.dart

@@ -109,57 +109,23 @@ class _Override {
 const Object override = const _Override();
 
 /**
- * The annotation `@Provisional('message')` marks a feature as provisional.
+ * An annotation class that was used during development of Dart 2.
  *
- * An API is considered to be provisional if it is still going through the
- * process of stabilizing and is subject to change or removal.
- *
- * The intent of the `@Provisional` annotation is to mark APIs that are still in
- * development or that are added only tentatively. Adding the API allows users
- * to experiment with using the APIs, which can provide valuable feedback. Such
- * provisional APIs do not promise stability. They can be changed or removed
- * without warning.
- *
- * The `@Provisional` annotation applies to:
- * - library directives,
- * - public top-level declarations, and
- * - public members of public classes.
- *
- * Provisionality is transitive:
- * - If a library is provisional, so is every member of it.
- * - If a class is provisional, so is every member of it.
- * - If a variable is provisional, so are its implicit getter and setter.
- *
- * Further, if a class is provisional, so are classes that extend, implement,
- * and mix-in the class.
- *
- * A tool that processes Dart source code may report when:
- * - the code imports a provisional library.
- * - the code exports a provisional library, or any provisional member of
- *   a non-provisional library.
- * - the code refers statically to a provisional declaration.
- * - the code dynamically uses a member of an object with a statically known
- *   type, where the member is provisional on the static type of the object.
- *
- * If the provisional use is inside a library, class or method which is itself
- * provisional, the tool should not bother the user about it.
- * A provisional feature is expected to use other provisional features.
+ * Should not be used any more.
  */
+@deprecated
 class Provisional {
-  /**
-   * A brief message describing how or why the feature is provisional.
-   */
-  final String message;
-
-  const Provisional({String message})
-      : this.message = message ?? "Subject to change or removal.";
+  String get message => null;
+  const Provisional({String message});
 }
 
 /**
- * Marks a feature as provisional with the message "Subject to change or
- * removal".
+ * An annotation that was used during development of Dart 2.
+ *
+ * Should not be used any more.
  */
-const Provisional provisional = const Provisional();
+@deprecated
+const Null provisional = null;
 
 class _Proxy {
   const _Proxy();