go spec: relaxed syntax for array, slice, and map composite literals

For elements which are themselves composite literals, the type may
be omitted if it is identical to the element type of the containing
composite literal.

R=r, rsc, iant, ken2
CC=golang-dev
https://golang.org/cl/2661041

diff --git a/doc/go_spec.html b/doc/go_spec.html
index 2373490c249c44208e0a09d8b5ce7d002799c51d..41368309de2b09621da31812f3f8c60e40f4f971 100644 (file)
--- a/doc/go_spec.html
+++ b/doc/go_spec.html
@@ -1,5 +1,5 @@
 <!-- title The Go Programming Language Specification -->
-<!-- subtitle Version of Sep 28, 2010 -->
+<!-- subtitle Version of Oct 21, 2010 -->
 
 <!--
 TODO
@@ -1971,15 +1971,16 @@ a single expression or a key-value pair.
 </p>
 
 <pre class="ebnf">
-CompositeLit  = LiteralType "{" [ ElementList [ "," ] ] "}" .
+CompositeLit  = LiteralType LiteralValue .
 LiteralType   = StructType | ArrayType | "[" "..." "]" ElementType |
                 SliceType | MapType | TypeName .
+LiteralValue  = "{" [ ElementList [ "," ] ] "}" .
 ElementList   = Element { "," Element } .
 Element       = [ Key ":" ] Value .
 Key           = FieldName | ElementIndex .
 FieldName     = identifier .
 ElementIndex  = Expression .
-Value         = Expression .
+Value         = Expression | LiteralValue .
 </pre>
 
 <p>
@@ -2093,6 +2094,17 @@ and is a shortcut for a slice operation applied to an array literal:
 [n]T{x1, x2, ... xn}[0 : n]
 </pre>
 
+<p>
+Within a composite literal of array, slice, or map type <code>T</code>,
+elements that are themselves composite literals may elide the respective
+literal type if it is identical to the element type of <code>T</code>.
+</p>
+
+<pre>
+[...]Point{{1.5, -3.5}, {0, 0}}  // same as [...]Point{Point{1.5, -3.5}, Point{0, 0}}
+[][]int{{1, 2, 3}, {4, 5}}       // same as [][]int{[]int{1, 2, 3}, []int{4, 5}}
+</pre>
+
 <p>
 A parsing ambiguity arises when a composite literal using the
 TypeName form of the LiteralType appears between the