using System;

class MyAttribute : Attribute
{}

partial class Stuff<[My]T> // Merge partial declarations
{
}
partial class Stuff<[My]T>
{
}

Result:

using System;

class MyAttribute : Attribute
{}

internal class Stuff<T> where T : 
{}

Attribute [My] has gone away.
Also, wrong 'where' clause added.

Issue was closed