spec: define order of multiple assignment
R=golang-dev, r, gri
CC=golang-dev
https://golang.org/cl/5240055
diff --git a/doc/go_spec.html b/doc/go_spec.html
index 310efe3..395d218 100644
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -1,5 +1,5 @@
<!-- title The Go Programming Language Specification -->
-<!-- subtitle Version of September 29, 2011 -->
+<!-- subtitle Version of October 13, 2011 -->
<!--
TODO
@@ -3730,14 +3730,32 @@
In the second form, the number of operands on the left must equal the number
of expressions on the right, each of which must be single-valued, and the
<i>n</i>th expression on the right is assigned to the <i>n</i>th
-operand on the left.
-The expressions on the right are evaluated before assigning to
-any of the operands on the left, but otherwise the evaluation
-order is unspecified beyond <a href="#Order_of_evaluation">the usual rules</a>.
+operand on the left. The assignment proceeds in two phases.
+First, the operands of <a href="#Indexes">index expressions</a>
+and <a href="#Address_operators">pointer indirections</a>
+(including implicit pointer indirections in <a href="#Selectors">selectors</a>)
+on the left and the expressions on the right are all
+<a href="#Order_of_evaluation">evaluated in the usual order</a>.
+Second, the assignments are carried out in left-to-right order.
</p>
<pre>
a, b = b, a // exchange a and b
+
+x := []int{1, 2, 3}
+i := 0
+i, x[i] = 1, 2 // set i = 1, x[0] = 2
+
+i = 0
+x[i], i = 2, 1 // set x[0] = 2, i = 1
+
+x[0], x[0] = 1, 2 // set x[0] = 1, then x[0] = 2 (so x[0] = 2 at end)
+
+x[1], x[3] = 4, 5 // set x[1] = 4, then panic setting x[3] = 5.
+
+type Point struct { x, y int }
+var p *Point
+x[2], p.x = 6, 7 // set x[2] = 6, then panic setting p.x = 7
</pre>
<p>
