<!--{
"Title": "The Go Programming Language Specification",
- "Subtitle": "Version of March 30, 2022",
+ "Subtitle": "Version of April 19, 2022",
"Path": "/ref/spec"
}-->
<p>
Every type that is a member of the type set of an interface implements that interface.
Any given type may implement several distinct interfaces.
-For instance, all types implement the <i>empty interface</i> which stands for the set of all types:
+For instance, all types implement the <i>empty interface</i> which stands for the set
+of all (non-interface) types:
</p>
<pre>
of its interface elements.
</li>
- <li>The type set of a method specification is the set of types
+ <li>The type set of a method specification is the set of all non-interface types
whose method sets include that method.
</li>
</li>
<li>The type set of a term of the form <code>~T</code>
- is the set of types whose underlying type is <code>T</code>.
+ is the set of all types whose underlying type is <code>T</code>.
</li>
<li>The type set of a <i>union</i> of terms
</li>
</ul>
+<p>
+The quantification "the set of all non-interface types" refers not just to all (non-interface)
+types declared in the program at hand, but all possible types in all possible programs, and
+hence is infinite.
+Similarly, given the set of all non-interface types that implement a particular method, the
+intersection of the method sets of those types will contain exactly that method, even if all
+types in the program at hand always pair that method with another method.
+</p>
+
<p>
By construction, an interface's type set never contains an interface type.
</p>