Migration: do not union inferred types in overrides.

Previously, when handling an override such as:

  abstract class A {
    int/*?*/ f();
  }
  class C implements A {
    f() => 0;
  }

we would create a union edge between the implicit return type of C.f
and the explicit return type of A.f.  This was a problem because
nullability information can propagate bidirectionally through union
edges, so it could result in types unnecessarily becoming nullable,
e.g.:

  abstract class A {
    int/*?*/ f();
  }
  abstract class B {
    int f(); // Should not need to be made nullable
  }
  class C implements A, B {
    f() => 0;
  }

This CL fixes the problem by just making ordinary unidirectional edges
for overrides involving inferred types.

Change-Id: I63a5f1f640b5543fcf39304087592e984aa66694
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/141853
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Mike Fairhurst <mfairhurst@google.com>
4 files changed
tree: a5a58e3da218c7e81a674a89908e1b146889a0a1
  1. .clang-format
  2. .dart_tool/
  3. .gitattributes
  4. .gitconfig
  5. .github/
  6. .gitignore
  7. .gn
  8. .mailmap
  9. .packages
  10. .style.yapf
  11. .vpython
  12. AUTHORS
  13. BUILD.gn
  14. CHANGELOG.md
  15. CONTRIBUTING.md
  16. DEPS
  17. LICENSE
  18. PATENT_GRANT
  19. PRESUBMIT.py
  20. README.dart-sdk
  21. README.md
  22. WATCHLISTS
  23. benchmarks/
  24. build/
  25. client/
  26. codereview.settings
  27. docs/
  28. pkg/
  29. runtime/
  30. samples-dev/
  31. samples/
  32. sdk/
  33. sdk_args.gni
  34. sdk_nnbd/
  35. tests/
  36. third_party/
  37. tools/
  38. utils/
README.md

Dart

A client-optimized language for fast apps on any platform

Dart is:

  • Optimized for UI: Develop with a programming language specialized around the needs of user interface creation

  • Productive: Make changes iteratively: use hot reload to see the result instantly in your running app

  • Fast on all platforms: Compile to ARM & x64 machine code for mobile, desktop, and backend. Or compile to JavaScript for the web

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 the dart.dev to learn more about the language, tools, getting started, and more.

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

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 on our wiki.

Contributing to Dart

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

You can also contribute patches, as described in Contributing.