bring back `#[derive(Show)]` with a deprecation warning

diff --git a/src/libsyntax/ext/deriving/mod.rs b/src/libsyntax/ext/deriving/mod.rs
index 2b7a44c172792a3c1de688d0bd3346863ea21bce..d3d7fee3a189a19a578835ce1712b5b888c8d600 100644 (file)
--- a/src/libsyntax/ext/deriving/mod.rs
+++ b/src/libsyntax/ext/deriving/mod.rs
@@ -107,6 +107,14 @@ macro_rules! expand {
 
                             "Rand" => expand!(rand::expand_deriving_rand),
 
+                            "Show" => {
+                                cx.span_warn(titem.span,
+                                             "derive(Show) is deprecated \
+                                              in favor of derive(Debug)");
+
+                                expand!(show::expand_deriving_show)
+                            },
+
                             "Debug" => expand!(show::expand_deriving_show),
 
                             "Default" => expand!(default::expand_deriving_default),