FS-1016-unreserve-keywords.md

F# RFC FS-1016 - Revise the Reserved Keyword List

The design suggestion Revise the reserved keyword list has been marked "approved in principle". This RFC covers the detailed proposal for this suggestion.

• Approved in principle
• Details: discussion
• Implementation: Completed

Summary

We have had requests to revise the reserved keyword list, e.g.

The keyword "method" is currently reserved for future use. In many web programming scenarios "method" refers to the HTTP method (GET/POST) and the fact that you currently have to escape the keyword and write method is annoying. Calling function parameter "meth" instead works (though some people may find this an unfortunate naming ;-)), but it is against F# coding guidelines. And furthermore, this only helps when you're defining the API, but sometimes you need to consume C# API that already has "method" as optional argument. I think that the F# community is quite happy with using the name "member" for declaring all members (including methods, properties and events) and I don't really think there is a need for keeping "method" reserved.

Motivation

The motivation is to make sure that users hit the "reserved keyword" warning less often.

Detailed design

Unreserve the following keywords:

method  - the F# community are happy with 'member' to introduce methods
constructor - the F# community are happy with 'new' to introduce constructors
atomic - this was related to the fad for transactional memory circa 2006. In F# this would now be a library-defined computation expression
eager - this is no longer needed, it was initially designed to be "let eager" to match a potential "let lazy"
object  - there is no need to reserve this
recursive  - F# is happy using "rec"
functor  - If F# added parameterized modules, we would use "module M(args) = ..."
measure  - There is no specific reason to reserve this these days, the [<Measure>] attribute suffices
volatile - There is no specific reason to reserve this these days, the [<Volatile>] attribute suffices

Drawbacks

The main drawback is simply the cost of making the change and the churn in the language spec

Alternatives

We could just not do it. But it seems to make sense to revise this now several years have passed since the reservations were made

Unresolved questions

None