Local Generic Constraints

[YT-GameMaker]

I would like something similar to this:

void HandleReferenceType<T>(in T value) where T : class { }
void HandleValueType<T>(in T value) where T : struct { }
void HandleEnumType<T>(in T value) where T : unmanaged, Enum { }
void HandleCustomType<T>(in T value) where T : ICustom { }

[MethodImpl(MethodImplOptions.AggressiveInlining)]
void Handle<T>(in T value)
{
    if (T : ICustom)
        HandleCustomType(value);
    else if (T : unmanaged, Enum)
        HandleEnumType(value);
    else if (T : struct)
        HandleValueType(value);
    else if (T : class)
        HandleReferenceType(value);
    else
        throw new NotSupportedException();
}

As shown in this example, local generic constraints are replaced with true or false at compile time and are then optimized. Most importantly, if the local generic constraint is true, the corresponding block has the corresponding generic constraint, allowing the code within the block to compile correctly.

[wherewhere]

Want it. I think : can be is.

void HandleReferenceType<T>(in T value) where T : class { }
void HandleValueType<T>(in T value) where T : struct { }
void HandleEnumType<T>(in T value) where T : unmanaged, Enum { }
void HandleCustomType<T>(in T value) where T : ICustom { }

[MethodImpl(MethodImplOptions.AggressiveInlining)]
void Handle<T>(in T value) where T : class or struct or (unmanaged, Enum) or ICustom
{
    if (T is ICustom)
        HandleCustomType(value);
    else if (T is unmanaged and Enum)
        HandleEnumType(value);
    else if (T is struct)
        HandleValueType(value);
    else if (T is class)
        HandleReferenceType(value);
    else
        throw new NotSupportedException();
}

[YT-GameMaker]

Using : would be consistent with generic constraints, and then you could just copy and paste :-) Alternatively, from another perspective, making generic constraints support 'is' would work.

[HaloFour]

See: #6308