fix bug where we could not accept constants as sizes in array_refs!

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "arrayref"
-version = "0.3.1"
+version = "0.3.2"
 authors = ["David Roundy <roundyd@physics.oregonstate.edu>"]
 description = "Macros to take array references of slices"
 license = "BSD-2-Clause"

examples/array_refs.rs

@@ -0,0 +1,13 @@
+#[macro_use]
+extern crate arrayref;
+
+fn main() {
+    let x = [0,1,2,3,4,5,6,7,8,9];
+    let (a,b,c) = array_refs!(&x, 2, 3, 5);
+    assert_eq!(2, a.len());
+    assert_eq!(3, b.len());
+    assert_eq!(5, c.len());
+    assert_eq!(*a, [0,1]);
+    assert_eq!(*b, [2,3,4]);
+    assert_eq!(*c, [5,6,7,8,9]);
+}

examples/array_refs_with_const.rs

@@ -0,0 +1,18 @@
+#[macro_use]
+extern crate arrayref;
+
+const SIZE: usize = 10;
+const SIZE_A: usize = 2;
+const SIZE_B: usize = 3;
+const SIZE_C: usize = 5;
+
+fn main() {
+    let x: [u8; SIZE] = [0,1,2,3,4,5,6,7,8,9];
+    let (a,b,c) = array_refs!(&x, SIZE_A, SIZE_B, SIZE_C);
+    assert_eq!(SIZE_A, a.len());
+    assert_eq!(SIZE_B, b.len());
+    assert_eq!(SIZE_C, c.len());
+    assert_eq!(*a, [0,1]);
+    assert_eq!(*b, [2,3,4]);
+    assert_eq!(*c, [5,6,7,8,9]);
+}

src/lib.rs

@@ -45,11 +45,6 @@ macro_rules! array_ref {
 /// me ensure that my sub-arrays add up to the entire array.  This
 /// macro will *never* panic, since the sizes are all checked at
 /// compile time.
-///
-/// I believe there are some interesting and exciting bugs that show
-/// up when you use lengths that are constants rather than numeric
-/// literals.  This should be fixable, but it will all be nicer when I
-/// can create actual doc tests.
 #[macro_export]
 macro_rules! array_refs {
     ( $arr:expr, $( $len:expr ),* ) => {{
@@ -60,7 +55,7 @@ macro_rules! array_refs {
                 let mut p = a.as_ptr();
                 ( $( {
                     let aref = &*(p as *const [T; $len]);
-                    p = p.offset($len);
+                    p = p.offset($len as isize);
                     aref
                 } ),* )
             }
@@ -81,11 +76,6 @@ macro_rules! array_refs {
 /// This is intentional, as I find it handy to make me ensure that my
 /// sub-arrays add up to the entire array.  This macro will *never*
 /// panic, since the sizes are all checked at compile time.
-///
-/// I believe there are some interesting and exciting bugs that show
-/// up when you use lengths that are constants rather than numeric
-/// literals.  This should be fixable, but it will all be nicer when I
-/// can create actual doc tests.
 #[macro_export]
 macro_rules! mut_array_refs {
     ( $arr:expr, $( $len:expr ),* ) => {{
@@ -96,7 +86,7 @@ macro_rules! mut_array_refs {
                 let mut p = a.as_mut_ptr();
                 ( $( {
                     let aref = &mut *(p as *mut [T; $len]);
-                    p = p.offset($len);
+                    p = p.offset($len as isize);
                     aref
                 } ),* )
             }