[analyzer] Represent `FutureOr<...>` as `FutureOrTypeImpl`.

This change introduces the class `FutureOrTypeImpl` to represent the
special types of the form `FutureOr<...>`, which were previously
represented as ordinary instances of `InterfaceType`.

This class mirrors the CFE's `FutureOrType` class. Adding it will
facilitate further code sharing between the analyzer and the CFE,
because it will allow code that's shared between the analyzer and CFE
to use `is` tests to recognize `FutureOr` types.

In a follow-up CL I intend to add a base class that is common to
analyzer and CFE `FutureOrType` representations.

Note that in https://dart-review.googlesource.com/c/sdk/+/396320, when
I introduced the `NullTypeImpl` class, I took pains to find all the
places in the analyzer that might call the `InterfaceTypeImpl`
constructor, and updated them so that if the type they are creating is
the `Null` type, they call the `NullTypeImpl` constructor
instead. That was tractable for the type `Null`, since there's
basically just a single `Null` type corresponding to a single
declaration in `dart:core`. At first I tried doing a similar thing for
`FutureOr`, but it proved to be a big pain, because `FutureOr` types
get created all over the place. It was difficult to be confident that
I'd updated all the necessary call sites. So instead I've put the
necessary logic in the `InterfaceTypeImpl` constructor itself (by
changing it into a factory constructor). This is a much lower risk
approach and I'm much happier with it. In a follow-up CL I'll change
the logic for `NullTypeImpl` to follow the same factory approach.

Change-Id: I54c6998f991456199076faeac995e433cc88845d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/396523
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
2 files changed
tree: 5f4bc95a286fed32a5aa8601839736cfa327b3f5
  1. .dart_tool/
  2. .github/
  3. benchmarks/
  4. build/
  5. docs/
  6. pkg/
  7. runtime/
  8. samples/
  9. sdk/
  10. tests/
  11. third_party/
  12. tools/
  13. utils/
  14. .clang-format
  15. .gitattributes
  16. .gitconfig
  17. .gitignore
  18. .gn
  19. .mailmap
  20. .style.yapf
  21. AUTHORS
  22. BUILD.gn
  23. CHANGELOG.md
  24. codereview.settings
  25. CONTRIBUTING.md
  26. DEPS
  27. LICENSE
  28. OWNERS
  29. PATENT_GRANT
  30. PRESUBMIT.py
  31. README.dart-sdk
  32. README.md
  33. sdk.code-workspace
  34. sdk_args.gni
  35. sdk_packages.yaml
  36. SECURITY.md
  37. WATCHLISTS
README.md

Dart

An approachable, portable, and productive language for high-quality apps on any platform

Dart is:

  • Approachable: Develop with a strongly typed programming language that is consistent, concise, and offers modern language features like null safety and patterns.

  • Portable: Compile to ARM, x64, or RISC-V machine code for mobile, desktop, and backend. Compile to JavaScript or WebAssembly for the web.

  • Productive: Make changes iteratively: use hot reload to see the result instantly in your running app. Diagnose app issues using DevTools.

Dart's flexible compiler technology lets you run Dart code in different ways, depending on your target platform and goals:

  • Dart Native: For programs targeting devices (mobile, desktop, server, and more), Dart Native includes both a Dart VM with JIT (just-in-time) compilation and an AOT (ahead-of-time) compiler for producing machine code.

  • Dart Web: For programs targeting the web, Dart Web includes both a development time compiler (dartdevc) and a production time compiler (dart2js).

Dart platforms illustration

License & patents

Dart is free and open source.

See LICENSE and PATENT_GRANT.

Using Dart

Visit dart.dev to learn more about the language, tools, and to find codelabs.

Browse pub.dev for more packages and libraries contributed by the community and the Dart team.

Our API reference documentation is published at api.dart.dev, based on the stable release. (We also publish docs from our beta and dev channels, as well as from the primary development branch).

Building Dart

If you want to build Dart yourself, here is a guide to getting the source, preparing your machine to build the SDK, and building.

There are more documents in our repo at docs.

Contributing to Dart

The easiest way to contribute to Dart is to file issues.

You can also contribute patches, as described in Contributing.

Roadmap

Future plans for Dart are included in the combined Dart and Flutter roadmap on the Flutter wiki.