Create version of the array repeat proposal specific to [x; ..N], as …

…a backup plan.

text/0000-new-array-repeat-syntax.md

@@ -5,9 +5,9 @@
 # Summary
 
 Under this RFC, the syntax to specify the type of a fixed-length array
-containing `N` elements of type `T` would be changed to `[T; N]`. Similarly, the
-syntax to construct an array containing `N` duplicated elements of value `x`
-would be changed to `[x; N]`.
+containing `N` elements of type `T` would be changed to `[T; ..N]`. Similarly,
+the syntax to construct an array containing `N` duplicated elements of value `x`
+would be changed to `[x; ..N]`.
 
 # Motivation
 
@@ -26,14 +26,14 @@ modifications that would make the range syntax less intuitive.
 # Detailed design
 
 The syntax `[T, ..N]` for specifying array types will be replaced by the new
-syntax `[T; N]`.
+syntax `[T; ..N]`.
 
 In the expression `[x, ..N]`, the `..N` will refer to an expression of type
 `RangeTo<T>` (where `T` is the type of `N`). As with any other array of two
 elements, `x` will have to be of the same type, and the array expression will be
-of type `[RangeTo<T>; 2]`.
+of type `[RangeTo<T>; ..2]`.
 
-The expression `[x; N]` will be equivalent to the old meaning of the syntax
+The expression `[x; ..N]` will be equivalent to the old meaning of the syntax
 `[x, ..N]`. Specifically, it will create an array of length `N`, each element of
 which has the value `x`.
 
@@ -46,7 +46,7 @@ let a: [uint, ..2] = [0u, ..2];
 to this:
 
 ```rust
-let a: [uint; 2] = [0u; 2];
+let a: [uint; ..2] = [0u; ..2];
 ```
 
 ## Match patterns
@@ -60,7 +60,7 @@ interpreted as a wildcard, and never as sugar for a range constructor.
 
 While not required by this RFC, one suggested transition plan is as follows:
 
-- Implement the new syntax for `[T; N]`/`[x; N]` proposed above.
+- Implement the new syntax for `[T; ..N]`/`[x; ..N]` proposed above.
 
 - Issue deprecation warnings for code that uses `[T, ..N]`/`[x, ..N]`, allowing
   easier identification of code that needs to be transitioned.
@@ -108,10 +108,13 @@ be no advocates of this alternative so far.
 ## Different array repeat syntax
 
 The comments in [pull request #498](https://github.com/rust-lang/rfcs/pull/498)
-mentioned many candidates for new syntax other than the `[x; N]` form in this
+mentioned many candidates for new syntax other than the `[x; ..N]` form in this
 RFC. The comments on the pull request of this RFC mentioned many more.
 
-- Instead of using `[x; N]`, use `[x for N]`.
+- Omit the `..`, since it is no longer necessary for disambiguation (a repeat
+  would therefore be spelled `[x; N]`).
+
+- Instead of using `[x; ..N]`, use `[x for N]`.
 
     - This use of `for` would not be exactly analogous to existing `for` loops,
       because those accept an iterator rather than an integer. To a new user,
@@ -165,7 +168,7 @@ enough to introduce further changes to separate the two. Or this could be
 considered innocuous enough to introduce some additional range-related meaning
 for `..` in certain patterns.
 
-It is possible that the new syntax `[x; N]` could itself be used within
+It is possible that the new syntax `[x; ..N]` could itself be used within
 patterns.
 
 This RFC does not attempt to address any of these issues, because the current