syntax: pretty print bind_by_value patterns as "copy", r=burningtree.

Author: graydon

src/libsyntax/print/pprust.rs

@@ -1555,8 +1555,10 @@ fn print_pat(s: ps, &&pat: @ast::pat) {
           ast::bind_by_move => {
             word_nbsp(s, ~"move");
           }
-          ast::bind_by_implicit_ref |
-          ast::bind_by_value => {}
+          ast::bind_by_value => {
+            word_nbsp(s, ~"copy");
+          }
+          ast::bind_by_implicit_ref => {}
         }
         print_path(s, path, true);
         match sub {