librustc: Remove copy expressions from the language.

src/libsyntax/print/pprust.rs

@@ -1344,7 +1344,6 @@ pub fn print_expr(s: @ps, expr: &ast::expr) {
         ibox(s, 0u);
         print_block(s, blk);
       }
-      ast::expr_copy(e) => { word_space(s, "copy"); print_expr(s, e); }
       ast::expr_assign(lhs, rhs) => {
         print_expr(s, lhs);
         space(s.s);