Utils/lang_feature_check.dart

// Copyright (c) 2018, 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.

part of Expect;

typedef F<X> = void Function<Y extends X>();

typedef expected_target = Function<X>();

// Functions for correct type comparison in language feature tests
F<X> toF<X>(X x) => <Y extends X>() {};
Type typeOf<X>() => X;

// Function to check nnbd_top_merge feature
class CHECK_TOP_MERGE<T> {
  T Function(T) get f => (x) => x;
}

// Functions to check least and greatest closures
// See https://github.com/dart-lang/co19/issues/575#issuecomment-613542349
Type? _capturedTypeArgument;

X captureTypeArgument<X>() {
  _capturedTypeArgument = X;
  throw "Error";
}

Type? get capturedTypeArgument {
  var result = _capturedTypeArgument;
  _capturedTypeArgument = null;
  return result;
}

// Sound/Unsound null safety flags (formerly known as weak/strong mode)
bool get hasUnsoundNullSafety => const <Null>[] is List<Object>;
bool get hasSoundNullSafety => !hasUnsoundNullSafety;