FIX: Simplify azip!() trailing comma rule - use new macro feature $()?

Author: bluss

src/zip/zipmacro.rs

@@ -101,32 +101,25 @@
 /// ```
 #[macro_export]
 macro_rules! azip {
-    // Indexed with a single producer and no trailing comma.
-    ((index $index:pat, $first_pat:pat in $first_prod:expr) $body:expr) => {
+    // Indexed with a single producer
+    // we allow an optional trailing comma after the producers in each rule.
+    ((index $index:pat, $first_pat:pat in $first_prod:expr $(,)?) $body:expr) => {
         $crate::Zip::indexed($first_prod).apply(|$index, $first_pat| $body)
     };
-    // Indexed with more than one producer and no trailing comma.
-    ((index $index:pat, $first_pat:pat in $first_prod:expr, $($pat:pat in $prod:expr),*) $body:expr) => {
+    // Indexed with more than one producer
+    ((index $index:pat, $first_pat:pat in $first_prod:expr, $($pat:pat in $prod:expr),* $(,)?) $body:expr) => {
         $crate::Zip::indexed($first_prod)
             $(.and($prod))*
             .apply(|$index, $first_pat, $($pat),*| $body)
     };
-    // Indexed with trailing comma.
-    ((index $index:pat, $($pat:pat in $prod:expr),+,) $body:expr) => {
-        azip!((index $index, $($pat in $prod),+) $body)
-    };
-    // Unindexed with a single producer and no trailing comma.
-    (($first_pat:pat in $first_prod:expr) $body:expr) => {
+    // Unindexed with a single producer
+    (($first_pat:pat in $first_prod:expr $(,)?) $body:expr) => {
         $crate::Zip::from($first_prod).apply(|$first_pat| $body)
     };
-    // Unindexed with more than one producer and no trailing comma.
-    (($first_pat:pat in $first_prod:expr, $($pat:pat in $prod:expr),*) $body:expr) => {
+    // Unindexed with more than one producer
+    (($first_pat:pat in $first_prod:expr, $($pat:pat in $prod:expr),* $(,)?) $body:expr) => {
         $crate::Zip::from($first_prod)
             $(.and($prod))*
             .apply(|$first_pat, $($pat),*| $body)
     };
-    // Unindexed with trailing comma.
-    (($($pat:pat in $prod:expr),+,) $body:expr) => {
-        azip!(($($pat in $prod),+) $body)
-    };
 }

tests/azip.rs

@@ -49,6 +49,16 @@ fn test_azip2_3() {
     assert!(a != b);
 }
 
+#[test]
+fn test_azip_syntax_trailing_comma() {
+    let mut b = Array::<i32, _>::zeros((5, 5));
+    let mut c = Array::<i32, _>::ones((5, 5));
+    let a = b.clone();
+    azip!((b in &mut b, c in &mut c, ) swap(b, c));
+    assert_eq!(a, c);
+    assert!(a != b);
+}
+
 #[test]
 #[cfg(feature = "approx")]
 fn test_azip2_sum() {