spec: add another sentence about BOMs

Although one may argue that they should be legal, gc (at least)
disallows byte order marks that are not the first code point
in the file. Added a sentence to the "Implementation restriction"
clause in the "Source code representation" section to document
this better.

Lifting this restriction (again - the rule has changed at least
twice already) would not break any existing programs, should
we later decide yet again to fiddle the rules about these little
fly specks.

R=golang-dev, dsymonds, gri
CC=golang-dev
https://golang.org/cl/8649043

diff --git a/doc/go_spec.html b/doc/go_spec.html
index 214d1c0acc4e634253b7c1734cf3defc6bef7be1..5cc452d2080fb2fa9874c43b516c2953d708e2cd 100644 (file)
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -1,6 +1,6 @@
 <!--{
        "Title": "The Go Programming Language Specification",
-       "Subtitle": "Version of April 3, 2013",
+       "Subtitle": "Version of April 10, 2013",
        "Path": "/ref/spec"
 }-->
 
@@ -103,6 +103,7 @@ compiler may disallow the NUL character (U+0000) in the source text.
 Implementation restriction: For compatibility with other tools, a
 compiler may ignore a UTF-8-encoded byte order mark
 (U+FEFF) if it is the first Unicode code point in the source text.
+A byte order mark may be disallowed anywhere else in the source.
 </p>
 
 <h3 id="Characters">Characters</h3>