Merge pull request rust-lang#2912 from topecongiro/fix-slice-pattern

Do not show wildcard pattern in slice pattern

Author: nrc

src/patterns.rs

@@ -144,7 +144,8 @@ impl Rewrite for Pat {
                 let prefix = prefix.iter().map(|p| p.rewrite(context, shape));
                 let slice_pat = slice_pat
                     .as_ref()
-                    .map(|p| Some(format!("{}..", p.rewrite(context, shape)?)));
+                    .and_then(|p| p.rewrite(context, shape))
+                    .map(|rw| Some(format!("{}..", if rw == "_" { "" } else { &rw })));
                 let suffix = suffix.iter().map(|p| p.rewrite(context, shape));
 
                 // Munge them together.

tests/source/pattern.rs

@@ -63,3 +63,11 @@ fn combine_patterns() {
         _ => return,
     };
 }
+
+fn slice_patterns() {
+    match b"123" {
+        [0, ..] => {}
+        [0, foo..] => {}
+        _ => {}
+    }
+}

tests/target/pattern.rs

@@ -75,3 +75,11 @@ fn combine_patterns() {
         _ => return,
     };
 }
+
+fn slice_patterns() {
+    match b"123" {
+        [0, ..] => {}
+        [0, foo..] => {}
+        _ => {}
+    }
+}