Provide better names for builtin deriving-generated attributes

src/libsyntax_ext/deriving/cmp/ord.rs

@@ -38,7 +38,7 @@ pub fn expand_deriving_ord(cx: &mut ExtCtxt,
                           name: "cmp",
                           generics: LifetimeBounds::empty(),
                           explicit_self: borrowed_explicit_self(),
-                          args: vec![borrowed_self()],
+                          args: vec![(borrowed_self(), "other")],
                           ret_ty: Literal(path_std!(cx, cmp::Ordering)),
                           attributes: attrs,
                           is_unsafe: false,

src/libsyntax_ext/deriving/cmp/partial_eq.rs

@@ -71,7 +71,7 @@ pub fn expand_deriving_partial_eq(cx: &mut ExtCtxt,
                 name: $name,
                 generics: LifetimeBounds::empty(),
                 explicit_self: borrowed_explicit_self(),
-                args: vec![borrowed_self()],
+                args: vec![(borrowed_self(), "_other")],
                 ret_ty: Literal(path_local!(bool)),
                 attributes: attrs,
                 is_unsafe: false,

src/libsyntax_ext/deriving/cmp/partial_ord.rs

@@ -34,7 +34,7 @@ pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
                 name: $name,
                 generics: LifetimeBounds::empty(),
                 explicit_self: borrowed_explicit_self(),
-                args: vec![borrowed_self()],
+                args: vec![(borrowed_self(), "other")],
                 ret_ty: Literal(path_local!(bool)),
                 attributes: attrs,
                 is_unsafe: false,
@@ -59,7 +59,7 @@ pub fn expand_deriving_partial_ord(cx: &mut ExtCtxt,
         name: "partial_cmp",
         generics: LifetimeBounds::empty(),
         explicit_self: borrowed_explicit_self(),
-        args: vec![borrowed_self()],
+        args: vec![(borrowed_self(), "other")],
         ret_ty,
         attributes: attrs,
         is_unsafe: false,

src/libsyntax_ext/deriving/debug.rs

@@ -40,7 +40,7 @@ pub fn expand_deriving_debug(cx: &mut ExtCtxt,
                           name: "fmt",
                           generics: LifetimeBounds::empty(),
                           explicit_self: borrowed_explicit_self(),
-                          args: vec![fmtr],
+                          args: vec![(fmtr, "_f")],
                           ret_ty: Literal(path_std!(cx, fmt::Result)),
                           attributes: Vec::new(),
                           is_unsafe: false,

src/libsyntax_ext/deriving/decodable.rs

@@ -67,8 +67,8 @@ fn expand_deriving_decodable_imp(cx: &mut ExtCtxt,
                                                             PathKind::Global)])],
                           },
                           explicit_self: None,
-                          args: vec![Ptr(Box::new(Literal(Path::new_local(typaram))),
-                                         Borrowed(None, Mutability::Mutable))],
+                          args: vec![(Ptr(Box::new(Literal(Path::new_local(typaram))),
+                                         Borrowed(None, Mutability::Mutable)), "d")],
                           ret_ty:
                               Literal(Path::new_(pathvec_std!(cx, result::Result),
                                                  None,

src/libsyntax_ext/deriving/encodable.rs

@@ -148,8 +148,8 @@ fn expand_deriving_encodable_imp(cx: &mut ExtCtxt,
                     ],
                 },
                 explicit_self: borrowed_explicit_self(),
-                args: vec![Ptr(Box::new(Literal(Path::new_local(typaram))),
-                           Borrowed(None, Mutability::Mutable))],
+                args: vec![(Ptr(Box::new(Literal(Path::new_local(typaram))),
+                           Borrowed(None, Mutability::Mutable)), "s")],
                 ret_ty: Literal(Path::new_(
                     pathvec_std!(cx, result::Result),
                     None,

src/libsyntax_ext/deriving/generic/mod.rs

@@ -252,7 +252,7 @@ pub struct MethodDef<'a> {
     pub explicit_self: Option<Option<PtrTy<'a>>>,
 
     /// Arguments other than the self argument
-    pub args: Vec<Ty<'a>>,
+    pub args: Vec<(Ty<'a>, &'a str)>,
 
     /// Return type
     pub ret_ty: Ty<'a>,
@@ -915,9 +915,9 @@ impl<'a> MethodDef<'a> {
             explicit_self
         });
 
-        for (i, ty) in self.args.iter().enumerate() {
+        for (ty, name) in self.args.iter() {
             let ast_ty = ty.to_ty(cx, trait_.span, type_ident, generics);
-            let ident = cx.ident_of(&format!("__arg_{}", i));
+            let ident = cx.ident_of(name).gensym();
             arg_tys.push((ident, ast_ty));
 
             let arg_expr = cx.expr_ident(trait_.span, ident);

src/libsyntax_ext/deriving/hash.rs

@@ -44,8 +44,8 @@ pub fn expand_deriving_hash(cx: &mut ExtCtxt,
                               bounds: vec![(typaram, vec![path_std!(cx, hash::Hasher)])],
                           },
                           explicit_self: borrowed_explicit_self(),
-                          args: vec![Ptr(Box::new(Literal(arg)),
-                                         Borrowed(None, Mutability::Mutable))],
+                          args: vec![(Ptr(Box::new(Literal(arg)),
+                                         Borrowed(None, Mutability::Mutable)), "_state")],
                           ret_ty: nil_ty(),
                           attributes: vec![],
                           is_unsafe: false,

src/libsyntax_pos/symbol.rs

@@ -53,6 +53,10 @@ impl Ident {
     pub fn modern(self) -> Ident {
         Ident::new(self.name, self.span.modern())
     }
+
+    pub fn gensym(self) -> Ident {
+        Ident::new(self.name.gensymed(), self.span)
+    }
 }
 
 impl PartialEq for Ident {

src/test/run-pass-fulldeps/auxiliary/custom_derive_partial_eq.rs

@@ -58,7 +58,7 @@ fn expand_deriving_partial_eq(cx: &mut ExtCtxt, span: Span, mitem: &MetaItem, it
         name: "eq",
         generics: LifetimeBounds::empty(),
         explicit_self: borrowed_explicit_self(),
-        args: vec![borrowed_self()],
+        args: vec![(borrowed_self(), "other")],
         ret_ty: Literal(deriving::generic::ty::Path::new_local("bool")),
         attributes: attrs,
         is_unsafe: false,