Expand support for byref to match C# 7

[baronfel]

Expand support for byref to match C# 7 [11125137]

Submitted by Keith Battocchi on 12/17/2015 12:00:00 AM
14 votes on UserVoice prior to migration

C# is adding support for byref locals and returns (see dotnet/roslyn#118, slated for milestone 1.3). This will result in many libraries that expose these features (which the CLR already supports), but methods with such return types aren't currently usable from F#. F# already supports byref locals, but doesn't support implementing byref-returning methods nor does it support calling byref-returning methods.
At a minimum, F# should support calling byref-returning-methods (e.g. SomeRefReturningMethod(x,y,z) <- w), since C# users will be creating methods like these and being unable to call them will limit F#'s reach.
It would be nice if on top of that base level of support F# also supported declaring such methods, using the same safety rules that C# is using (e.g. the only refs that are safe to return are those that point to values stored on the heap or existing refs that are passed into the method).

Response

** by fslang-admin on 1/23/2016 12:00:00 AM **

Yes, this should be done, thanks
Approved in primciple subject to a detailed design, resolution of any remaining issues, and an implementation, with testing. Also subject to the feature actually appearing in C# 7 :)
Don Syme, F# Language Evolution

Original UserVoice Submission
Archived Uservoice Comments

[dsyme]

See the RFC here, now completed https://github.com/fsharp/fslang-design/blob/master/RFCs/FS-1020-byref-returns.md