spec: corrections to various sections

- fix definition of "specific types" and add more examples
- state that a parameterized function must be instantiated
  when used as a function value
- remove duplicate word ("can can" -> "can")

Thanks to @danscales for finding these.

Change-Id: Ideb41efc35a3e67694d3bc97e462454feae37c44
Reviewed-on: https://go-review.googlesource.com/c/go/+/367394
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

diff --git a/doc/go_spec.html b/doc/go_spec.html
index 4700548cb25321b0f2b4874f1d521e48e97d954a..11f44d896d50f83fbe516d073b6690d32fad3062 100644 (file)
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -1,6 +1,6 @@
 <!--{
        "Title": "The Go Programming Language Specification - Go 1.18 Draft (incomplete)",
-       "Subtitle": "Version of Nov 24, 2021",
+       "Subtitle": "Version of Nov 29, 2021",
        "Path": "/ref/spec"
 }-->
 
@@ -1971,39 +1971,38 @@ x                   T           x is not representable by a value of T because
 
 <p>
 An interface specification which contains <a href="#Interface_types">type elements</a>
-that are not interface types defines a (possibly empty) set of <i>specific types</i>.
+defines a (possibly empty) set of <i>specific types</i>.
 Loosely speaking, these are the types <code>T</code> that appear in the
 interface definition in terms of the form <code>T</code>, <code>~T</code>,
 or in unions of such terms.
 </p>
 
 <p>
-More precisely, for a given interface, the set of specific types is defined as follows:
+More precisely, for a given interface, the set 𝑆 of specific types is defined as follows:
 </p>
 
 <ul>
-       <li>The set of specific types of the empty interface is the empty set.
+       <li>For an interface with no type elements, 𝑆 is the empty set.
        </li>
 
-       <li>The set of specific types of a non-empty interface is the intersection
-               of the specific types of its interface elements.
+       <li>For an interface with type elements, 𝑆 is the intersection
+               of the specific types of its type elements.
        </li>
 
-       <li>The set of specific types of a method specification is the empty set.
+       <li>For a non-interface type term <code>T</code>
+               or <code>~T</code>, 𝑆 is the set consisting of the type <code>T</code>.
        </li>
 
-       <li>The set of specific types of a non-interface type term <code>T</code>
-               or <code>~T</code> is the set consisting of the type <code>T</code>.
-       </li>
-
-       <li>The set of specific types of a <i>union</i> of terms
-               <code>t<sub>1</sub>|t<sub>2</sub>|…|t<sub>n</sub></code>
-               is the union of the specific types of the terms.
+       <li>For a <i>union</i> of terms
+               <code>t<sub>1</sub>|t<sub>2</sub>|…|t<sub>n</sub></code>,
+               𝑆 is the union of the specific types of the terms.
        </li>
 </ul>
 
 <p>
-If the set of specific types is empty, the interface has <i>no specific types</i>.
+If 𝑆 is empty, the interface has <i>no specific types</i>.
+An interface may have specific types even if its <a href="#Interface_types">type set</a>
+is empty.
 </p>
 
 <p>
@@ -2019,6 +2018,8 @@ interface{ int }               // int
 interface{ ~string }           // string
 interface{ int|~string }       // int, string
 interface{ Celsius|Kelvin }    // Celsius, Kelvin
+interface{ int; m() }          // int (but type set is empty because int has no method m)
+interface{ int; any }          // no specific types (intersection is empty)
 interface{ int; string }       // no specific types (intersection is empty)
 </pre>
 
@@ -3980,7 +3981,8 @@ pt.Scale(3.5)     // method call with receiver pt
 
 <p>
 If <code>f</code> denotes a parameterized function, it must be
-<a href="#Instantiations">instantiated</a> before it can be called.
+<a href="#Instantiations">instantiated</a> before it can be called
+or used as a function value.
 </p>
 
 <p>
@@ -4807,7 +4809,7 @@ Only <code>V</code> is a type parameter and a value of each
 specific type of <code>V</code> can be converted to <code>T</code>.
 </li>
 <li>
-Only <code>T</code> is a type parameter and <code>x</code> can can be converted to each
+Only <code>T</code> is a type parameter and <code>x</code> can be converted to each
 specific type of <code>T</code>.
 </li>
 </ul>