Support for protected members in classes #688
Merged
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
This change adds support for protected members in classes as proposed in #1. Also, this change introduces better error messages for assignability and subtype checks involving private and optional properties.
Protected members are modeled after C# and Java. Protected members can be accessed only within the declaring class and subclasses of the declaring class. Furthermore, access to a protected instance member is required to take place through an instance of the enclosing class type or a class type constructed from it (this prevents "sibling" class access).
Protected members can be made public in derived classes. Similar to private members, constructors and signature members cannot be protected.
I will follow up with a more formal specification of the rules but wanted to put up the code for folks to experiment with.
Update: Formal specification provided in #700.