Add Capabilities and Constraints as part of the effort to bring Effects into the language

[Suminda Dharmasena]

Is there a possibility to consider capabilities and contraints. This can also use the same infrastructure used to define effects depending on how they are implemented.

A practical implementation of it is found in Pony (http://www.ponylang.org/): http://tutorial.ponylang.org/capabilities/index.html. Also X10 (http://x10-lang.org/) has constraint types: sec 4.5 - http://x10.sourceforge.net/documentation/languagespec/x10-latest.pdf.

[Suminda Dharmasena]

Containt typing in X10 Language (Sec 4.5 - http://x10.sourceforge.net/documentation/languagespec/x10-latest.pdf) is form of Dependent Typing which is very useful. It will be good if constraints can make it into the language. The incremental effort to add this since  singleton types will be in the language is minimum but will be very useful.