spec: be precise about rune/string literals and comments

See #10248 for details.

Fixes #10248.

Change-Id: I373545b2dca5d1da1c7149eb0a8f6c6dd8071a4c
Reviewed-on: https://go-review.googlesource.com/10503Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

doc/go_spec.html

 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Version of June 23, 2015",
+	"Subtitle": "Version of July 23, 2015",
 	"Path": "/ref/spec"
 }-->
 
@@ -129,27 +129,27 @@ hex_digit     = "0" … "9" | "A" … "F" | "a" … "f" .
 <h3 id="Comments">Comments</h3>
 
 <p>
-There are two forms of comments:
+Comments serve as program documentation. There are two forms:
 </p>
 
 <ol>
 <li>
 <i>Line comments</i> start with the character sequence <code>//</code>
-and stop at the end of the line. A line comment acts like a newline.
+and stop at the end of the line.
 </li>
 <li>
 <i>General comments</i> start with the character sequence <code>/*</code>
-and continue through the character sequence <code>*/</code>. A general
-comment containing one or more newlines acts like a newline, otherwise it acts
-like a space.
+and stop with the first subsequent character sequence <code>*/</code>.
 </li>
 </ol>
 
 <p>
-Comments do not nest.
+A comment cannot start inside a <a href="#Rune_literals">rune</a> or
+<a href="#String_literals">string literal</a>, or inside a comment.
+A general comment containing no newlines acts like a space.
+Any other comment acts like a newline.
 </p>
 
-
 <h3 id="Tokens">Tokens</h3>
 
 <p>
@@ -176,11 +176,8 @@ using the following two rules:
 
 <ol>
 <li>
-<p>
 When the input is broken into tokens, a semicolon is automatically inserted
-into the token stream at the end of a non-blank line if the line's final
-token is
-</p>
+into the token stream immediately after a line's final token if that token is
 <ul>
 	<li>an
 	    <a href="#Identifiers">identifier</a>
@@ -357,9 +354,10 @@ imaginary_lit = (decimals | float_lit) "i" .
 <p>
 A rune literal represents a <a href="#Constants">rune constant</a>,
 an integer value identifying a Unicode code point.
-A rune literal is expressed as one or more characters enclosed in single quotes.
-Within the quotes, any character may appear except single
-quote and newline. A single quoted character represents the Unicode value
+A rune literal is expressed as one or more characters enclosed in single quotes,
+as in <code>'x'</code> or <code>'\n'</code>.
+Within the quotes, any character may appear except newline and unescaped single
+quote. A single quoted character represents the Unicode value
 of the character itself,
 while multi-character sequences beginning with a backslash encode
 values in various formats.
@@ -433,6 +431,7 @@ escaped_char     = `\` ( "a" | "b" | "f" | "n" | "r" | "t" | "v" | `\` | "'" | `
 '\xff'
 '\u12e4'
 '\U00101234'
+'\''         // rune literal containing single quote character
 'aa'         // illegal: too many characters
 '\xa'        // illegal: too few hexadecimal digits
 '\0'         // illegal: too few octal digits
@@ -449,8 +448,8 @@ obtained from concatenating a sequence of characters. There are two forms:
 raw string literals and interpreted string literals.
 </p>
 <p>
-Raw string literals are character sequences between back quotes
-<code>``</code>.  Within the quotes, any character is legal except
+Raw string literals are character sequences between back quotes, as in
+<code>`foo`</code>.  Within the quotes, any character may appear except
 back quote. The value of a raw string literal is the
 string composed of the uninterpreted (implicitly UTF-8-encoded) characters
 between the quotes;
@@ -461,8 +460,9 @@ are discarded from the raw string value.
 </p>
 <p>
 Interpreted string literals are character sequences between double
-quotes <code>&quot;&quot;</code>. The text between the quotes,
-which may not contain newlines, forms the
+quotes, as in <code>&quot;bar&quot;</code>.
+Within the quotes, any character may appear except newline and unescaped double quote.
+The text between the quotes forms the
 value of the literal, with backslash escapes interpreted as they
 are in <a href="#Rune_literals">rune literals</a> (except that <code>\'</code> is illegal and
 <code>\"</code> is legal), with the same restrictions.
@@ -488,7 +488,7 @@ interpreted_string_lit = `"` { unicode_value | byte_value } `"` .
 `\n
 \n`                  // same as "\\n\n\\n"
 "\n"
-""
+"\""                 // same as `"`
 "Hello, world!\n"
 "日本語"
 "\u65e5本\U00008a9e"