Allow to omit generic type parameters partially

[DrPepperBianco]

Currently in CSharp if you have a generic method with multiple generic type parameters. You can either have to pass all type parameters explicitly or omit all parameters, if they can be derived implicitly.
If only a part of the type parameters can be derived implicitly you still have to pass them explicitly.

Example:

Lets say we have a result interface like this:

interface IResult<TValue> 
{
    public IReadOnlyList<Exception> Exceptions { get; }
    public TValue? ValueOrDefault { get; }
}

No I have an extension method like this:

public static IResult<TOut> Convert<TIn, TOut>(this IResult<TIn> result) =>
    new ResultImpl<TOut>
    {
        Exceptions = result.Exceptions,
        ValueOrDefault = default
    };

If I want to use this extension method I have to explicitly set both generic parameters:

IResult<string> result = TryGetString();
IResult<int> intResult = result.Convert<string, int>();

Instead it would be helpful, if we could just omit the first parameter, like this for example:

IResult<string> result = TryGetString();
IResult<int> intResult = result.Convert<_, int>();```

or this:

IResult<string> result = TryGetString();
IResult<int>  intResult = result.Convert<?, int>();

or this:

IResult<string> result = TryGetString();
IResult<int> intResult = result.Convert<, int>();

[333fred]

Duplicate of #8968.

[DrPepperBianco]

Thanks, didn’t found the other one myself.