Discussion: Named type arguments

[alrz]

Named type arguments

Proposal: dotnet/roslyn#6207

Named type arguments are useful for various use cases:

• When only a few type parameters cannot be inferred.

U F<T, U>(T t) { .. }

var x = F<U:short>(1); // F<int, short>

• To specify a few default type parameters (Discussion: default type parameters #278)

class C<T = X, U = Y> {}

new C<U: Z>();

• Or just for clarity,

var x = F<TResult: int>();

Again, just like named arguments, named type arguments do not need to be in the same order that they are declared, as long as all non-default type parameters are specified.

void F<T, U, V = C>() {}

F<U: A, T: B>();

It will be possible to mix positional and named type arguments,

F<A, U:B>();