Additional tests of `??=` coercion behaviors for `inference-update-3`.

The tests for the language feature `inference-update-3` are adjusted
to verify that the following hold true for an if-null expression of
the form `e1 ??= e2`:

- If the static type of `e2` is not a subtype of the write type of
  `e1`, but it is assignable via a coercion, then the coercion is
  performed, and the coerced type of `e2` is used to compute the
  static type of the whole `??=` expression.

- If `e1` is a promoted local variable, then coercions are performed
  based solely on the declared (unpromoted) type of `e1`.

These behaviors apply regardless of whether feature
`inference-update-3` is enabled; accordingly, this commit updates both
the `_test.dart` and `_disabled_test.dart` variants of the tests. I've
manually verified that even with the work on `inference-update-3`
reverted, the `_disabled_test.dart` tests continue to pass, so we can
be reasonably certain that these behaviors pre-date the work on the
`inference-update-3` feature.

Note: the diff is large due to the fact that the front end has 6
different code paths for handling `??=`, depending on the form of the
LHS, so to make sure that we have adequate test coverage, there are
tests for every possible LHS form. However, the diffs for all the
tests are pretty much the same except for
`if_null_assignment_local_disabled_test.dart` and
`if_null_assignment_local_test.dart`, which have extra test cases to
cover promotion behaviors.

Bug: https://github.com/dart-lang/language/issues/1618
Change-Id: I711d62d9dc00fc20a2efd3967d60066d9bfaec03
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/356303
Reviewed-by: Lasse Nielsen <lrn@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
46 files changed
tree: 046d03d703b99a0870f6e658161a5ef2748fa1aa
  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. SECURITY.md
  36. 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).

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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.

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You can also contribute patches, as described in Contributing.