doc: add illegal octal over 255 example

Octal values over 255, like \400 or \777, are illegal.  It wasn't clear if the expected behavior was a compile error, encoding the value as two characters, or if the value would be capped at 255.

This example explicitly shows that octal values over 255 are illegal.

Change-Id: I45d94680107029c5f083e5d434e6270cc5b258c1
GitHub-Last-Rev: f6bef0379f547ca6204c837279d67ad87c2b69c7
GitHub-Pull-Request: golang/go#52111
Reviewed-on: https://go-review.googlesource.com/c/go/+/397555
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>

diff --git a/doc/go_spec.html b/doc/go_spec.html
index 2255b6f8e2464d291d4ecda9da97b3486117db84..9da1f6ad9987a17c682578c8931548811f7e2dc3 100644 (file)
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -529,6 +529,7 @@ escaped_char     = `\` ( "a" | "b" | "f" | "n" | "r" | "t" | "v" | `\` | "'" | `
 'aa'         // illegal: too many characters
 '\xa'        // illegal: too few hexadecimal digits
 '\0'         // illegal: too few octal digits
+'\400'       // illegal: octal value over 255
 '\uDFFF'     // illegal: surrogate half
 '\U00110000' // illegal: invalid Unicode code point
 </pre>