Proposal: Require named arguments

Say we have a method or constructor with many parameters of the same type:

public Foo(int a, int b, int c, int d)
{
    ...
}

And creating an instance:

new Foo(
    a: 1,
    b: 2,
    c: 3,
    d: 4);

This comes up most often for constructors of immutable types.

The warning could show when the following criteria are met:

• More than 3 arguments.
• Each argument on their own row.
• At least two adjacent arguments are of the same type.
• Not in an expression tree.

Wrote it here if anyone wants to play with it. Think it is a good fit in StyleCop though.

[ArthurHNL]

I would argue that the warning should not be fired when the argument name is equal to the name of the variable that is used as the argument:

public void DoSomething(int a, int b, int c)
{
}

public void SomeMethod()
{
   int a = 1;
   int foo = 2;
   int d = 3;

   DoSomething(
      a, // No warning, argument name is the same as variable name.
      foo, // Warning, no argument name is provided AND the argument name is not equal to the argument name.
      c: d); // No warning, argument name is provided.
}

This sort of “copies” the behaviour of ReSharper, ReSharper shows the argument name in the code when it is not specified and the variable used as argument does not have the same name as the argument.

[sharwell]

💭 I wonder how helpful a “StyleCop Extras” project would be, where many of the code-style-related subjective rules that get requested could be developed.