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Commit 9f70bc7

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Add Future.syncValue(T value) constructor.
There is currently no way to create a future with a specific value that doesn't accept a `FutureOr` argument, and tries to flatten it. The `Future.syncValue(T value)` constructor does not accept a `Future<T>`, which makes it easier to control the type and argument. It may also be more efficient than constructors which need to first check if the argument is a `Future<T>` (and `_Future<T>`) first. You shouldn't create a `Future<Future<Object>>`, but you might for testing, and this constructor makes that easier too. (It should really be called `Future.value`, but that name was taken by what should probably have been `Future.new`.) See https://dartbug.com/59814 for performance considerations. CoreLibraryReviewExempt: No platform specific code or new functionality. Change-Id: Ib5728055a06b20433dcd448ca7ad1baa54ec681c Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/451022 Reviewed-by: Nate Bosch <nbosch@google.com> Commit-Queue: Lasse Nielsen <lrn@google.com>
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‎CHANGELOG.md‎

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### Libraries
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#### `dart:async`
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- Added `Future.syncValue` constructor for creating a future with a
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known value. Unlike `Future.value`, it does not allow an asynchronous
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`Future<T>` as the value of a new `Future<T>`.
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#### `dart:core`
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- **Breaking Change** [#61392][]: The `Uri.parseIPv4Address` function

‎sdk/lib/async/future.dart‎

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@@ -294,21 +294,31 @@ abstract interface class Future<T> {
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return result;
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}
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/// Returns a future containing the result of immediately calling
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/// [computation].
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/// The result of calling [computation] as a future.
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///
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/// If calling [computation] throws, the returned future is completed with the
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/// error.
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/// Mainly used when working with functions returning a `FutureOr<T>`,
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/// or non-async functions in a non-`async` asynchronous function,
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/// where you want to capture any error in a future.
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///
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/// If calling [computation] throws, the returned future is completed
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/// with the error.
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///
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/// If calling [computation] returns a `Future<T>`, that future is returned.
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///
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/// If calling [computation] returns a non-future value,
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/// a future is returned which has been completed with that value.
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/// If calling [computation] returns a non-`Future<T>` value,
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/// a future is created which has been completed with that value.
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///
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/// Example:
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/// ```dart
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/// final result = await Future<int>.sync(() => 12);
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/// Future<int> asyncAdd(
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/// FutureOr<int> Function() a,
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/// FutureOr<int> Function() b,
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/// ) =>
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/// (Future.sync(a), Future.sync(b)).wait.then((ab) => ab.1ドル + ab.2ドル);
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/// ```
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///
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/// To create a future with a known value, use [Future.syncValue] instead,
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/// as `Future.syncValue(12)`.
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factory Future.sync(FutureOr<T> computation()) {
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FutureOr<T> result;
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try {
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return result is Future<T> ? result : _Future<T>.value(result);
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}
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/// Creates a future completed with [value].
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///
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/// The future is guaranteed to not have an error.
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///
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/// If a synchronous computation can throw,
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/// rather than doing `Future.syncValue(computation())` and wrapping that in
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/// a `try`/`catch`, you can use [Future.sync] which catches an error
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/// into its returned future, as `Future.sync(() => computation())`.
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@Since("3.10")
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factory Future.syncValue(T value) => _Future<T>().._setValue(value);
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/// Creates a future completed with [value].
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///
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/// If [value] is a future, the created future waits for the

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