Return 'this' proposal (original) (raw)

Joseph D. Darcy Joe.Darcy at Sun.COM
Tue Mar 17 15:48:26 PDT 2009

Marek KozieĊ‚ wrote:

2009/3/17 Joseph D. Darcy <Joe.Darcy at sun.com <mailto:Joe.Darcy at sun.com>>

This 'this' proposal remains vague and imprecise. Including this type/self type in a language is a continuing area of study; for example, see the recent paper "Matching ThisType to Subtyping," Chieri Saito and Atsushi Igarashi, Kyoto University, Japan, ACM SAC 2009. There are open bugs requesting this capability. For example typing "site:bugs.sun.com <http://bugs.sun.com> this type" into a popular search engine quickly yields, amongst other hits, 6479372 Add self types (type of 'this' aka ThisClass) to the language This bug discusses the size of the type system impact of this change, a magnitude far too large for Project Coin. There is no need to submit further refinements of this idea; any proposal along the lines of adding a this type will be out of scope for Project Coin. -Joe

I'll check it, but I'm afraid that introducing 'This' type will be impossible for Java and for all other languages with Inheritance, or I would say it's possible but conditions would be huge. return 'this': - Idea is quite simple: you use object from left side of dot as returned from method, it's the same quite idea with converting void -> this, but allowed only when it's written directly. - Byte-code for that is other story and I'm not sure how much limitation this contains. Maybe you cold while what problems you see (that could help)?

As the author and submitter of a proposal, it is your responsibility to research, understand, and explain the consequences and implications of your proposal.

-Joe

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