fsharp / fsharp/fslang-suggestions

Allow implementation of generic methods with constraints of the form 'T :> 'U

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#255 34 comments 66 reactions 1 assignee Claimed by @abelbraaksma View on GitHub
approved-in-principle area: interop area: object-programming old votes:50-200
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Description

# Allow implementation of generic methods with constraints of the form 'T :> 'U [5927125]

**Submitted by Gusty on 5/14/2014 12:00:00 AM**
**136 votes on UserVoice prior to migration**

Currently this is solved as 'a = 'b.
This limitation does not exists in C# and it makes impossible to interact with some existing libraries, as in this case http://stackoverflow.com/questions/23643989/is-it-possible-to-implement-the-idbsett-interface-in-f
This will also allow to work around F#'s lack of generic (co/contra)-variance.

**[Original UserVoice Submission](https://fslang.uservoice.com/forums/245727-f-language/suggestions/5927125)**
[Archived Uservoice Comments](../tree/master/archive/suggestion-5927125-allow-implementation-of-generic-methods-with-cons.md#comments)

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