fsharp
Generic struct type whose fields are all unmanaged types is unmanaged
Generic struct type whose fields are all unmanaged types is unmanaged
A non-generic struct type whose fields are all unmanaged types is unmanaged.
into
A generic struct type whose fields are all unmanaged types is unmanaged.
as
The unmanaged constraint on generic type T enforces the type to be an 'unmanaged' struct that does not recursively contain reference type fields.
as for cases
type Cell<'T when 'T: unmanaged> =
struct
val element: 'T
val next: nativeptr<Cell<'T>>
end
type UnmanagedCell<'T when 'T: unmanaged> =
struct
end
[<EntryPoint>]
let main argv =
let fine = UnmanagedCell<int>()
let FS0001 = UnmanagedCell<UnmanagedCell<int>>()
0
The existing way of approaching this problem in F# is prevent compilation with error
error FS0001: A generic construct requires that the type 'X' is an unmanaged type
I have asked the question on SO and found that it is F# limitation, not CLR.
Pros and Cons
See Related suggestions
Extra information
Related suggestions: https://github.com/dotnet/csharplang/issues/1504 https://github.com/dotnet/csharplang/issues/1649
Affidavit (please submit!)
Please tick this by placing a cross in the box:
- [x ] This is not a question (e.g. like one you might ask on stackoverflow) and I have searched stackoverflow for discussions of this issue
- [x] I have searched both open and closed suggestions on this site and believe this is not a duplicate
- [x] This is not something which has obviously "already been decided" in previous versions of F#. If you're questioning a fundamental design decision that has obviously already been taken (e.g. "Make F# untyped") then please don't submit it.
Please tick all that apply:
- [x] This is not a breaking change to the F# language design
- [ ] I or my company would be willing to help implement and/or test this
This is actually quite easy to implement and it should not be a breaking change. We should make this change to follow C#.
We would also need to interop with C# by looking at the IsUnmanagedAttribute on the type argument and be able to emit it as well.
For reference, here's a link to the original PR for C#, which is now merged: https://github.com/dotnet/roslyn/pull/31148.
Edit: apparently more work was done on several PR's, here's all: https://github.com/dotnet/roslyn/commits/features/unmanaged-constructed-types.
This was done via https://github.com/dotnet/fsharp/pull/12154, this suggestion can be closed.
