Proposal: Static Generics

[hez2010]

Proposal: Static Generics

For people who are not familiar with Static Generics, please see https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/generics/statically-resolved-type-parameters

Proposed syntax

Use inline to mark the functions/classes are resolved from caller,'T for static generic type parameters.

inline void 'T Foo<'T>('T x, 'T y)
{
    return x + y; // requires static member '+'
}

void Main()
{
    var x = Foo(5, 6); // 11
    var y = Foo("Hel", "lo"); // "Hello"
    var z = Foo(new { }, 234); // error
}

[Richiban]

This functionality will hopefully be provided by the shapes proposal. #164

[huoyaoyuan]

An enhancement of generic type system should have been planned for C# 10 (See Language Version Planning). We don't need to open new issues for specific scenarios, as the enhancement are supposed to be wider.

The language team is currently completing C# 9 that features records. Once C# 9 has been completed, they should be able to focus on the enhancement.

[333fred]

There is some type system improvement stuff triaged into 10, but I wouldn't expect anything really big until 11. Some of the stuff in 10 is there to make sure we talk about it during that time frame.

[Lemmingh]

Generic method has already made code analysis awkward sometimes, for example, locking.

I'm afraid the current proposal would introduce more hard-to-lint cases.

IMHO, restrictions should be added at least. What about:

• must not exceed internal.
• must specify type parameter constraints.

[YairHalberstadt]

Closing as being looked at as part of #164, #1711