Question

I have something like this

V Func<V>()
{
  // do stuff
  V res = default(V);
 // more stuff
  return res;
}

The problem is that I want res to be either 0 or a new instance of V

I tried creating 2 methods

Func<V> where T: new()
Func<V> where T: struct

but surprisingly this is not allowed

My workaround is to have 2 functions

FuncNew<V> where T: new()
...
res = new V();
....

and

FuncDefault<V> where T: struct
...
res = default(V)
...

EDIT: Summarize answers

new(T) will new up a ref or value type; I did not realize that

Answer 1

You can use the new() constraint:

private V Func<V>() where V : new()
{
  // do stuff
  V res = new V();
 // more stuff
  return res;
}

Value types will be initialized to all-zeros, and any reference types will be initialized using their no-args default constructor.

If the reference type doesn’t have a no-args constructor it can’t be used with this method, and you’ll have to use other ways (there are plenty of solutions to this problem elsewhere on SO, eg Passing arguments to C# generic new() of templated type)