Support implicit new and const in the analyzer

[bwilkerson]

In order to minimize the impact of these changes on clients of analyzer, it might be better to not change the AST structure, but to have the resolver rewrite the AST when it is able to interpret the syntax based on resolution information.

[bwilkerson]

I believe that this CL (https://dart-review.googlesource.com/c/sdk/+/31960) updates all of the code that assumed that the keyword would not be null to check for null.

The next step is to update the resolver to resolve constructors when the new/const keyword is missing and to re-write the AST as appropriate. That work will need to be behind a flag until other platforms start implementing this feature.

[bwilkerson]

This feature should be behind the --preview-dart-2 flag (after a new --use-cfe flag has replaced the current use of that flag) until the VM supports this syntax.

[devoncarew]

@jwren, can you update this with the progress for implicit new and const? Thanks!

[jwren]

@bwilkerson and I are working on this right now.

The flag changes mentioned above are done, and there is now support in the analysis_options.yaml file, adding the enablePreviewDart2 bit (in a recently built Dart SDK) and reanalyzing sources will yield the current status of where we are if you want to go try it out:

analyzer:
  language:
    enablePreviewDart2 : true

For correct errors and warnings with the implicit constructors, additional logic is required to know when some constructor is const, this change should land soon: https://dart-review.googlesource.com/c/sdk/+/38140

There are 8 cases to cover: [libraryPrefix.]?Class[<type-arguments>]?[.name]?()

The cases "Class()" and "Class.constructorName()" are currently working and required changes in the resolver of the analyzer.

I am working on the cases of "libraryPrefix.Class()" and "libraryPrefix.Class.constructorName()" now, which are also changes in the resolver.

The remaining cases (all cases) should be a changes in the parser only.

My best guess is that pending other tasks, this will be done into early next week.

[dgrove]

Any updates?

[bwilkerson]

I am waiting for some fixes to the tests to land (https://dart-review.googlesource.com/c/sdk/+/40301) so that the tests are correct. Then I can verify that my changes related to the recent spec change are correct and working.

[bwilkerson]

I believe that this is now implemented, though I'm sure we'll find a few bugs.