go spec: clarification of type declarations
R=r, rsc
CC=golang-dev
https://golang.org/cl/849044
diff --git a/doc/go_spec.html b/doc/go_spec.html
index 84480f6..4a4fa50 100644
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -1704,9 +1704,11 @@
<p>
A type declaration binds an identifier, the <i>type name</i>, to a new type
that has the same definition (element, fields, channel direction, etc.) as
-an existing type. The new type is
+an existing type. With the exception of interface types, the new type is
<a href="#Properties_of_types_and_values">compatible</a> with, but
<a href="#Properties_of_types_and_values">different</a> from, the existing type.
+A newly defined interface type is always
+<a href="#Properties_of_types_and_values">identical</a> to the existing type.
</p>
<pre class="ebnf">
@@ -1737,7 +1739,7 @@
<p>
The declared type does not inherit any <a href="#Method_declarations">methods</a>
bound to the existing type, but the <a href="#Types">method set</a>
-of elements of a composite type is not changed:
+of elements of a composite type or of an interface type is not changed:
</p>
<pre>
@@ -1754,6 +1756,10 @@
type PrintableMutex struct {
Mutex
}
+
+// MyCipher is an interface type that has the same method set as Cipher;
+// it is indistinguishable from Cipher.
+type MyCipher Cipher
</pre>
<p>
