variables, only on lexical <i>references</i> to them in the source,
analyzed transitively. For instance, if a variable <code>x</code>'s
initialization expression refers to a function whose body refers to
variable <code>y</code> then <code>x</code> depends on <code>y</code>.
Specifically:
</p>

<ul>
<li>
A reference to a variable or function is an identifier denoting that

</p>

<pre>
type T1[P T1[P]] …                    // illegal: T1 refers to itself
type T2[P interface{ T2[int] }] …     // illegal: T2 refers to itself
type T3[P interface{ m(T3[int])}] …   // illegal: T3 refers to itself
type T4[P T5[P]] …                    // illegal: T4 refers to T5 and
type T5[P T4[P]] …                    //          T5 refers to T4