spec: clarify prose for range over numeric range expressions
Fixes #66967.
Change-Id: I7b9d62dcb83bad60b2ce74e2e2bf1a36c6a8ae38
Reviewed-on: https://go-review.googlesource.com/c/go/+/581256
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Bypass: Robert Griesemer <gri@google.com>
diff --git a/doc/go_spec.html b/doc/go_spec.html
index f5069f6..ac27c1d 100644
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -1,6 +1,6 @@
<!--{
"Title": "The Go Programming Language Specification",
- "Subtitle": "Language version go1.22 (April 24, 2024)",
+ "Subtitle": "Language version go1.22 (April 25, 2024)",
"Path": "/ref/spec"
}-->
@@ -6656,13 +6656,13 @@
</p>
<pre class="grammar">
-Range expression 1st value 2nd value
+Range expression 1st value 2nd value
-array or slice a [n]E, *[n]E, or []E index i int a[i] E
-string s string type index i int see below rune
-map m map[K]V key k K m[k] V
-channel c chan E, <-chan E element e E
-integer n integer type value i see below
+array or slice a [n]E, *[n]E, or []E index i int a[i] E
+string s string type index i int see below rune
+map m map[K]V key k K m[k] V
+channel c chan E, <-chan E element e E
+integer value n integer type, or untyped int value i see below
</pre>
<ol>
@@ -6703,8 +6703,17 @@
</li>
<li>
-For an integer value <code>n</code>, the iteration values 0 through <code>n-1</code>
+For an integer value <code>n</code>, where <code>n</code> is of <a href="#Numeric_types">integer type</a>
+or an untyped <a href="#Constants">integer constant</a>, the iteration values 0 through <code>n-1</code>
are produced in increasing order.
+If <code>n</code> is of integer type, the iteration values have that same type.
+Otherwise, the type of <code>n</code> is determined as if it were assigned to the
+iteration variable.
+Specifically:
+if the iteration variable is preexisting, the type of the iteration values is the type of the iteration
+variable, which must be of integer type.
+Otherwise, if the iteration variable is declared by the "range" clause or is absent,
+the type of the iteration values is the <a href="#Constants">default type</a> for <code>n</code>.
If <code>n</code> <= 0, the loop does not run any iterations.
</li>
</ol>
@@ -6716,11 +6725,7 @@
In this case their <a href="#Declarations_and_scope">scope</a> is the block of the "for" statement
and each iteration has its own new variables [<a href="#Go_1.22">Go 1.22</a>]
(see also <a href="#For_clause">"for" statements with a ForClause</a>).
-If the range expression is a (possibly untyped) integer expression <code>n</code>,
-the variable has the same type as if it was
-<a href="#Variable_declarations">declared</a> with initialization
-expression <code>n</code>.
-Otherwise, the variables have the types of their respective iteration values.
+The variables have the types of their respective iteration values.
</p>
<p>
@@ -6728,9 +6733,6 @@
they must be preexisting.
In this case, the iteration values are assigned to the respective variables
as in an <a href="#Assignment_statements">assignment statement</a>.
-If the range expression is a (possibly untyped) integer expression <code>n</code>,
-<code>n</code> too must be <a href="#Assignability">assignable</a> to the iteration variable;
-if there is no iteration variable, <code>n</code> must be assignable to <code>int</code>.
</p>
<pre>
@@ -6778,6 +6780,10 @@
var u uint8
for u = range 256 {
}
+
+// invalid: 1e3 is a floating-point constant
+for range 1e3 {
+}
</pre>
