Remove gensyms from built-in derives

Also make them generally more hygienic with name resolution.

src/libsyntax_ext/deriving/cmp/ord.rs

@@ -43,17 +43,18 @@ pub fn expand_deriving_ord(cx: &mut ExtCtxt<'_>,
 }
 
 
-pub fn ordering_collapsed(cx: &mut ExtCtxt<'_>,
-                          span: Span,
-                          self_arg_tags: &[ast::Ident])
-                          -> P<ast::Expr> {
+pub fn ordering_collapsed(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    self_arg_tags: &[ast::Ident],
+) -> P<ast::Expr> {
     let lft = cx.expr_ident(span, self_arg_tags[0]);
     let rgt = cx.expr_addr_of(span, cx.expr_ident(span, self_arg_tags[1]));
-    cx.expr_method_call(span, lft, cx.ident_of("cmp"), vec![rgt])
+    cx.expr_method_call(span, lft, ast::Ident::new(sym::cmp, span), vec![rgt])
 }
 
 pub fn cs_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<Expr> {
-    let test_id = cx.ident_of("cmp").gensym();
+    let test_id = ast::Ident::new(sym::cmp, span);
     let equals_path = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
 
     let cmp_path = cx.std_path(&[sym::cmp, sym::Ord, sym::cmp]);
@@ -75,34 +76,34 @@ pub fn cs_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<
             // as the outermost one, and the last as the innermost.
             false,
             |cx, span, old, self_f, other_fs| {
-        // match new {
-        //     ::std::cmp::Ordering::Equal => old,
-        //     cmp => cmp
-        // }
+                // match new {
+                //     ::std::cmp::Ordering::Equal => old,
+                //     cmp => cmp
+                // }
 
-        let new = {
-            let other_f = match other_fs {
-                [o_f] => o_f,
-                _ => cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`"),
-            };
+                let new = {
+                    let other_f = match other_fs {
+                        [o_f] => o_f,
+                        _ => cx.span_bug(span, "not exactly 2 arguments in `derive(Ord)`"),
+                    };
 
-            let args = vec![
-                    cx.expr_addr_of(span, self_f),
-                    cx.expr_addr_of(span, other_f.clone()),
-                ];
+                    let args = vec![
+                            cx.expr_addr_of(span, self_f),
+                            cx.expr_addr_of(span, other_f.clone()),
+                        ];
 
-            cx.expr_call_global(span, cmp_path.clone(), args)
-        };
+                    cx.expr_call_global(span, cmp_path.clone(), args)
+                };
 
-        let eq_arm = cx.arm(span,
-                            vec![cx.pat_path(span, equals_path.clone())],
-                            old);
-        let neq_arm = cx.arm(span,
-                             vec![cx.pat_ident(span, test_id)],
-                             cx.expr_ident(span, test_id));
+                let eq_arm = cx.arm(span,
+                                    vec![cx.pat_path(span, equals_path.clone())],
+                                    old);
+                let neq_arm = cx.arm(span,
+                                     vec![cx.pat_ident(span, test_id)],
+                                     cx.expr_ident(span, test_id));
 
-        cx.expr_match(span, new, vec![eq_arm, neq_arm])
-    },
+                cx.expr_match(span, new, vec![eq_arm, neq_arm])
+            },
             cx.expr_path(equals_path.clone()),
             Box::new(|cx, span, (self_args, tag_tuple), _non_self_args| {
         if self_args.len() != 2 {

src/libsyntax_ext/deriving/cmp/partial_ord.rs

@@ -94,11 +94,12 @@ pub enum OrderingOp {
     GeOp,
 }
 
-pub fn some_ordering_collapsed(cx: &mut ExtCtxt<'_>,
-                               span: Span,
-                               op: OrderingOp,
-                               self_arg_tags: &[ast::Ident])
-                               -> P<ast::Expr> {
+pub fn some_ordering_collapsed(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    op: OrderingOp,
+    self_arg_tags: &[ast::Ident],
+) -> P<ast::Expr> {
     let lft = cx.expr_ident(span, self_arg_tags[0]);
     let rgt = cx.expr_addr_of(span, cx.expr_ident(span, self_arg_tags[1]));
     let op_str = match op {
@@ -108,11 +109,11 @@ pub fn some_ordering_collapsed(cx: &mut ExtCtxt<'_>,
         GtOp => "gt",
         GeOp => "ge",
     };
-    cx.expr_method_call(span, lft, cx.ident_of(op_str), vec![rgt])
+    cx.expr_method_call(span, lft, ast::Ident::from_str_and_span(op_str, span), vec![rgt])
 }
 
 pub fn cs_partial_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> P<Expr> {
-    let test_id = cx.ident_of("cmp").gensym();
+    let test_id = ast::Ident::new(sym::cmp, span);
     let ordering = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
     let ordering_expr = cx.expr_path(ordering.clone());
     let equals_expr = cx.expr_some(span, ordering_expr);

src/libsyntax_ext/deriving/debug.rs

@@ -62,7 +62,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
     // We want to make sure we have the ctxt set so that we can use unstable methods
     let span = span.with_ctxt(cx.backtrace());
     let name = cx.expr_lit(span, ast::LitKind::Str(ident.name, ast::StrStyle::Cooked));
-    let builder = Ident::from_str("debug_trait_builder").gensym();
+    let builder = Ident::from_str_and_span("debug_trait_builder", span);
     let builder_expr = cx.expr_ident(span, builder.clone());
 
     let fmt = substr.nonself_args[0].clone();
@@ -73,7 +73,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
             // tuple struct/"normal" variant
             let expr =
                 cx.expr_method_call(span, fmt, Ident::from_str("debug_tuple"), vec![name]);
-            stmts.push(cx.stmt_let(DUMMY_SP, true, builder, expr));
+            stmts.push(cx.stmt_let(span, true, builder, expr));
 
             for field in fields {
                 // Use double indirection to make sure this works for unsized types
@@ -82,7 +82,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
 
                 let expr = cx.expr_method_call(span,
                                                 builder_expr.clone(),
-                                                Ident::with_dummy_span(sym::field),
+                                                Ident::new(sym::field, span),
                                                 vec![field]);
 
                 // Use `let _ = expr;` to avoid triggering the
@@ -106,7 +106,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
                 let field = cx.expr_addr_of(field.span, field);
                 let expr = cx.expr_method_call(span,
                                                 builder_expr.clone(),
-                                                Ident::with_dummy_span(sym::field),
+                                                Ident::new(sym::field, span),
                                                 vec![name, field]);
                 stmts.push(stmt_let_undescore(cx, span, expr));
             }

src/libsyntax_ext/deriving/decodable.rs

@@ -1,6 +1,6 @@
-//! The compiler code necessary for `#[derive(Decodable)]`. See encodable.rs for more.
+//! The compiler code necessary for `#[derive(RustcDecodable)]`. See encodable.rs for more.
 
-use crate::deriving::{self, pathvec_std};
+use crate::deriving::pathvec_std;
 use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
@@ -17,7 +17,7 @@ pub fn expand_deriving_rustc_decodable(cx: &mut ExtCtxt<'_>,
                                        item: &Annotatable,
                                        push: &mut dyn FnMut(Annotatable)) {
     let krate = "rustc_serialize";
-    let typaram = &*deriving::hygienic_type_parameter(item, "__D");
+    let typaram = "__D";
 
     let trait_def = TraitDef {
         span,

src/libsyntax_ext/deriving/encodable.rs

@@ -1,11 +1,12 @@
-//! The compiler code necessary to implement the `#[derive(Encodable)]`
-//! (and `Decodable`, in `decodable.rs`) extension. The idea here is that
-//! type-defining items may be tagged with `#[derive(Encodable, Decodable)]`.
+//! The compiler code necessary to implement the `#[derive(RustcEncodable)]`
+//! (and `RustcDecodable`, in `decodable.rs`) extension. The idea here is that
+//! type-defining items may be tagged with
+//! `#[derive(RustcEncodable, RustcDecodable)]`.
 //!
 //! For example, a type like:
 //!
 //! ```
-//! #[derive(Encodable, Decodable)]
+//! #[derive(RustcEncodable, RustcDecodable)]
 //! struct Node { id: usize }
 //! ```
 //!
@@ -40,15 +41,17 @@
 //! references other non-built-in types. A type definition like:
 //!
 //! ```
-//! # #[derive(Encodable, Decodable)] struct Span;
-//! #[derive(Encodable, Decodable)]
+//! # #[derive(RustcEncodable, RustcDecodable)]
+//! # struct Span;
+//! #[derive(RustcEncodable, RustcDecodable)]
 //! struct Spanned<T> { node: T, span: Span }
 //! ```
 //!
 //! would yield functions like:
 //!
 //! ```
-//! # #[derive(Encodable, Decodable)] struct Span;
+//! # #[derive(RustcEncodable, RustcDecodable)]
+//! # struct Span;
 //! # struct Spanned<T> { node: T, span: Span }
 //! impl<
 //!     S: Encoder<E>,
@@ -82,7 +85,7 @@
 //! }
 //! ```
 
-use crate::deriving::{self, pathvec_std};
+use crate::deriving::pathvec_std;
 use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
@@ -98,7 +101,7 @@ pub fn expand_deriving_rustc_encodable(cx: &mut ExtCtxt<'_>,
                                        item: &Annotatable,
                                        push: &mut dyn FnMut(Annotatable)) {
     let krate = "rustc_serialize";
-    let typaram = &*deriving::hygienic_type_parameter(item, "__S");
+    let typaram = "__S";
 
     let trait_def = TraitDef {
         span,

src/libsyntax_ext/deriving/generic/mod.rs

@@ -890,7 +890,7 @@ impl<'a> MethodDef<'a> {
 
         for (ty, name) in self.args.iter() {
             let ast_ty = ty.to_ty(cx, trait_.span, type_ident, generics);
-            let ident = cx.ident_of(name).gensym();
+            let ident = ast::Ident::from_str_and_span(name, trait_.span);
             arg_tys.push((ident, ast_ty));
 
             let arg_expr = cx.expr_ident(trait_.span, ident);
@@ -1210,7 +1210,7 @@ impl<'a> MethodDef<'a> {
         let vi_idents = self_arg_names.iter()
             .map(|name| {
                 let vi_suffix = format!("{}_vi", &name[..]);
-                cx.ident_of(&vi_suffix[..]).gensym()
+                ast::Ident::from_str_and_span(&vi_suffix[..], trait_.span)
             })
             .collect::<Vec<ast::Ident>>();
 
@@ -1387,7 +1387,10 @@ impl<'a> MethodDef<'a> {
                 let variant_value =
                     deriving::call_intrinsic(cx, sp, "discriminant_value", vec![self_addr]);
 
-                let target_ty = cx.ty_ident(sp, cx.ident_of(target_type_name));
+                let target_ty = cx.ty_ident(
+                    sp,
+                    ast::Ident::from_str_and_span(target_type_name, sp),
+                );
                 let variant_disr = cx.expr_cast(sp, variant_value, target_ty);
                 let let_stmt = cx.stmt_let(sp, false, ident, variant_disr);
                 index_let_stmts.push(let_stmt);
@@ -1588,7 +1591,7 @@ impl<'a> TraitDef<'a> {
         let mut ident_exprs = Vec::new();
         for (i, struct_field) in struct_def.fields().iter().enumerate() {
             let sp = struct_field.span.with_ctxt(self.span.ctxt());
-            let ident = cx.ident_of(&format!("{}_{}", prefix, i)).gensym();
+            let ident = ast::Ident::from_str_and_span(&format!("{}_{}", prefix, i), self.span);
             paths.push(ident.with_span_pos(sp));
             let val = cx.expr_path(cx.path_ident(sp, ident));
             let val = if use_temporaries {

src/libsyntax_ext/deriving/generic/ty.rs

@@ -72,7 +72,7 @@ impl<'a> Path<'a> {
                    self_ty: Ident,
                    self_generics: &Generics)
                    -> ast::Path {
-        let mut idents = self.path.iter().map(|s| cx.ident_of(*s)).collect();
+        let mut idents = self.path.iter().map(|s| Ident::from_str_and_span(*s, span)).collect();
         let lt = mk_lifetimes(cx, span, &self.lifetime);
         let tys: Vec<P<ast::Ty>> =
             self.params.iter().map(|t| t.to_ty(cx, span, self_ty, self_generics)).collect();
@@ -209,7 +209,7 @@ fn mk_ty_param(cx: &ExtCtxt<'_>,
             cx.trait_bound(path)
         })
         .collect();
-    cx.typaram(span, cx.ident_of(name), attrs.to_owned(), bounds, None)
+    cx.typaram(span, ast::Ident::from_str_and_span(name, span), attrs.to_owned(), bounds, None)
 }
 
 fn mk_generics(params: Vec<ast::GenericParam>, span: Span) -> Generics {

src/libsyntax_ext/deriving/hash.rs

@@ -16,7 +16,7 @@ pub fn expand_deriving_hash(cx: &mut ExtCtxt<'_>,
 
     let path = Path::new_(pathvec_std!(cx, hash::Hash), None, vec![], PathKind::Std);
 
-    let typaram = &*deriving::hygienic_type_parameter(item, "__H");
+    let typaram = "__H";
 
     let arg = Path::new_local(typaram);
     let hash_trait_def = TraitDef {

src/libsyntax_ext/deriving/mod.rs

@@ -54,33 +54,6 @@ impl MultiItemModifier for BuiltinDerive {
     }
 }
 
-/// Construct a name for the inner type parameter that can't collide with any type parameters of
-/// the item. This is achieved by starting with a base and then concatenating the names of all
-/// other type parameters.
-// FIXME(aburka): use real hygiene when that becomes possible
-fn hygienic_type_parameter(item: &Annotatable, base: &str) -> String {
-    let mut typaram = String::from(base);
-    if let Annotatable::Item(ref item) = *item {
-        match item.node {
-            ast::ItemKind::Struct(_, ast::Generics { ref params, .. }) |
-            ast::ItemKind::Enum(_, ast::Generics { ref params, .. }) => {
-                for param in params {
-                    match param.kind {
-                        ast::GenericParamKind::Type { .. } => {
-                            typaram.push_str(&param.ident.as_str());
-                        }
-                        _ => {}
-                    }
-                }
-            }
-
-            _ => {}
-        }
-    }
-
-    typaram
-}
-
 /// Constructs an expression that calls an intrinsic
 fn call_intrinsic(cx: &ExtCtxt<'_>,
                   span: Span,