[RelayCommand] does not work with partial methods

[Sergio0694]

Describe the bug

Using [RelayCommand] with partial methods incorrectly marks them as being overloads, and emits an error.

Regression

No.

Steps to reproduce

[RelayCommand]
private partial void Foo();

private partial void Foo()
{
}

private partial void Bar();

[RelayCommand]
private partial void Bar()
{
}

Expected behavior

The code should compile just fine.