Naked type aliases can add and name constraints

gistfile1.txt

// This F# language suggestion wants a way to name collections of constraints:
//    http://fslang.uservoice.com/forums/245727-f-language/suggestions/8509687-add-constraints-as-a-language-construct
//

// This is a type alias X<T> = T, so X<int> = int etc.
type X<'T> = 'T


// This is a type alias X<T> = T which adds a constraint
type WithStruct<'T when 'T : struct> = 'T

// Use it like this:
let f1 (x: WithStruct<'T>) : 'T = x

// This shows a type alias can imply multiple named constraintsm which gives a way of naming collections of constraints:
type WithFG< ^T when ^T : (member F : int -> unit)
                and ^T : (member G : int -> unit)  > = ^T

// Use it like this:
let inline f2 (x: WithFG< ^T >) = 
  (^T : (member F : int -> unit) (x, 1)) 
  (^T : (member G : int -> unit) (x, 2))

fsharp/fslang-suggestions#456

Let's discuss on discussion thread please https://github.com/fsharp/fslang-design/blob/main/RFCs/FS-1124-interfaces-with-static-abstract-members.md