public class Foo<T> where T : Bar // Generate class 'Bar'
{
}

public class Foo<T> where T : Bar // CS0703 Inconsistent accessibility: constraint type 'Bar' is less accessible than 'Foo<T>'
{
}

internal class Bar 
{
}

public class Foo<T> where T : Bar
{
}

public class Bar 
{
}