imp(arg_enum): enum declared with arg_enum returns [&'static str; #] …

…instead of Vec

src/lib.rs

@@ -1,3 +1,8 @@
+// Copyright ⓒ 2015-2016 Kevin B. Knapp and clap-rs contributors.
+// Licensed under the MIT license
+// (see LICENSE or <http://opensource.org/licenses/MIT>) All files in the project carrying such
+// notice may not be copied, modified, or distributed except according to those terms.
+
 //! A simple to use, efficient, and full featured library for parsing command line arguments and subcommands when writing console, or terminal applications.
 //!
 //! ## About

src/macros.rs

@@ -212,6 +212,35 @@ macro_rules! values_t_or_exit {
     };
 }
 
+// _clap_count_exprs! is derived from https://github.com/DanielKeep/rust-grabbag
+// commit: 82a35ca5d9a04c3b920622d542104e3310ee5b07
+// License: MIT
+// Copyright ⓒ 2015 grabbag contributors.
+// Licensed under the MIT license (see LICENSE or <http://opensource.org
+// /licenses/MIT>) or the Apache License, Version 2.0 (see LICENSE of
+// <http://www.apache.org/licenses/LICENSE-2.0>), at your option. All
+// files in the project carrying such notice may not be copied, modified,
+// or distributed except according to those terms.
+//
+/// Counts the number of comma-delimited expressions passed to it.  The result is a compile-time
+/// evaluable expression, suitable for use as a static array size, or the value of a `const`.
+///
+/// # Examples
+///
+/// ```
+/// # #[macro_use] extern crate clap;
+/// # fn main() {
+/// const COUNT: usize = _clap_count_exprs!(a, 5+1, "hi there!".into_string());
+/// assert_eq!(COUNT, 3);
+/// # }
+/// ```
+#[macro_export]
+macro_rules! _clap_count_exprs {
+    () => { 0 };
+    ($e:expr) => { 1 };
+    ($e:expr, $($es:expr),+) => { 1 + _clap_count_exprs!($($es),*) };
+}
+
 /// Convenience macro to generate more complete enums with variants to be used as a type when
 /// parsing arguments. This enum also provides a `variants()` function which can be used to
 /// retrieve a `Vec<&'static str>` of the variant names, as well as implementing `FromStr` and
@@ -284,8 +313,8 @@ macro_rules! arg_enum {
         }
         impl $e {
             #[allow(dead_code)]
-            pub fn variants() -> Vec<&'static str> {
-                vec![
+            pub fn variants() -> [&'static str; _clap_count_exprs!($(stringify!($v)),+)] {
+                [
                     $(stringify!($v),)+
                 ]
             }