Kallen Tu
8bfb683892
This CL enables the primary constructors feature by default in Dart 3.13.
The primary constructors feature is a brevity feature. There are no new semantics, but it allows us to express declarations in a less verbose way.
This feature allows one constructor and a set of instance variables to be specified in the header of a declaration.
Currently a declaration with a constructor and some fields is written as:
```dart
// Current syntax.
class Point {
int x;
int y;
Point(this.x, this.y);
}
```
With a primary constructor, we would write the above as:
```
class Point(var int x, var int y);
```
If a primary constructor needs an initializer list or a body, they can be
specified inside the class using the `this` body syntax:
```dart
class Point(var int x, var int y) {
this : assert(x >= 0) {
print('Point created at $x, $y');
}
}
```
As part of this feature, you can also use the `new` and `factory` keywords to
declare constructors in the class body without repeating the class name:
```dart
class Point {
int x, y;
// Equivalent to Point(this.x, this.y)
new(this.x, this.y);
// Equivalent to Point.origin()
new origin() : x = 0, y = 0;
// Equivalent to factory Point.clone(Point other)
factory clone(Point other) => Point(other.x, other.y);
}
```
To learn more about the feature, check out the feature specification located here: https://github.com/dart-lang/language/blob/main/accepted/future-releases/primary-constructors/feature-specification.md
Tested: Has existing language, CFE, analyzer, analysis server tests.
Bug: https://github.com/dart-lang/sdk/issues/61524
Change-Id: I296f2fcd918b87bf2a1dd00256340759866c2423
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/489241
Reviewed-by: Bob Nystrom <rnystrom@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Nicholas Shahan <nshahan@google.com>
Reviewed-by: Michael Thomsen <mit@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Kallen Tu <kallentu@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>
55 lines
1.4 KiB
C++
55 lines
1.4 KiB
C++
// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// NOTE: THIS FILE IS GENERATED. DO NOT EDIT.
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//
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// Instead modify 'tools/experimental_features.yaml' and run
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// 'dart tools/generate_experimental_flags.dart' to update.
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#ifndef RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
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#define RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
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namespace dart {
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enum class ExperimentalFeature {
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primary_constructors,
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private_named_parameters,
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dot_shorthands,
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native_assets,
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getter_setter_error,
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sound_flow_analysis,
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null_aware_elements,
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inference_using_bounds,
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wildcard_variables,
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digit_separators,
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inference_update_3,
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inline_class,
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inference_update_2,
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sealed_class,
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class_modifiers,
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records,
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patterns,
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unnamed_libraries,
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inference_update_1,
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enhanced_enums,
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named_arguments_anywhere,
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super_parameters,
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constructor_tearoffs,
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generic_metadata,
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triple_shift,
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nonfunction_type_aliases,
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non_nullable,
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extension_methods,
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constant_update_2018,
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control_flow_collections,
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set_literals,
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spread_collections,
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};
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bool GetExperimentalFeatureDefault(ExperimentalFeature feature);
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const char* GetExperimentalFeatureName(ExperimentalFeature feature);
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} // namespace dart
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#endif // RUNTIME_VM_EXPERIMENTAL_FEATURES_H_
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