Remove lifetime support in deriving code.

It's unused.

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -18,7 +18,6 @@ pub fn expand_deriving_partial_ord(
     let ordering_ty = Literal(path_std!(cmp::Ordering));
     let ret_ty = Literal(Path::new_(
         pathvec_std!(option::Option),
-        None,
         vec![Box::new(ordering_ty)],
         PathKind::Std,
     ));

compiler/rustc_builtin_macros/src/deriving/decodable.rs

@@ -23,7 +23,7 @@ pub fn expand_deriving_rustc_decodable(
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: Path::new_(vec![krate, sym::Decodable], None, vec![], PathKind::Global),
+        path: Path::new_(vec![krate, sym::Decodable], vec![], PathKind::Global),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,
@@ -32,19 +32,17 @@ pub fn expand_deriving_rustc_decodable(
             generics: Bounds {
                 bounds: vec![(
                     typaram,
-                    vec![Path::new_(vec![krate, sym::Decoder], None, vec![], PathKind::Global)],
+                    vec![Path::new_(vec![krate, sym::Decoder], vec![], PathKind::Global)],
                 )],
             },
             explicit_self: false,
             args: vec![(Ref(Box::new(Literal(Path::new_local(typaram))), Mutability::Mut), sym::d)],
             ret_ty: Literal(Path::new_(
                 pathvec_std!(result::Result),
-                None,
                 vec![
                     Box::new(Self_),
                     Box::new(Literal(Path::new_(
                         vec![typaram, sym::Error],
-                        None,
                         vec![],
                         PathKind::Local,
                     ))),

compiler/rustc_builtin_macros/src/deriving/encodable.rs

@@ -108,7 +108,7 @@ pub fn expand_deriving_rustc_encodable(
     let trait_def = TraitDef {
         span,
         attributes: Vec::new(),
-        path: Path::new_(vec![krate, sym::Encodable], None, vec![], PathKind::Global),
+        path: Path::new_(vec![krate, sym::Encodable], vec![], PathKind::Global),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),
         supports_unions: false,
@@ -117,19 +117,17 @@ pub fn expand_deriving_rustc_encodable(
             generics: Bounds {
                 bounds: vec![(
                     typaram,
-                    vec![Path::new_(vec![krate, sym::Encoder], None, vec![], PathKind::Global)],
+                    vec![Path::new_(vec![krate, sym::Encoder], vec![], PathKind::Global)],
                 )],
             },
             explicit_self: true,
             args: vec![(Ref(Box::new(Literal(Path::new_local(typaram))), Mutability::Mut), sym::s)],
             ret_ty: Literal(Path::new_(
                 pathvec_std!(result::Result),
-                None,
                 vec![
                     Box::new(Tuple(Vec::new())),
                     Box::new(Literal(Path::new_(
                         vec![typaram, sym::Error],
-                        None,
                         vec![],
                         PathKind::Local,
                     ))),

compiler/rustc_builtin_macros/src/deriving/generic/ty.rs

@@ -11,11 +11,10 @@ use rustc_span::symbol::{kw, Ident, Symbol};
 use rustc_span::Span;
 
 /// A path, e.g., `::std::option::Option::<i32>` (global). Has support
-/// for type parameters and a lifetime.
+/// for type parameters.
 #[derive(Clone)]
 pub struct Path {
     path: Vec<Symbol>,
-    lifetime: Option<Ident>,
     params: Vec<Box<Ty>>,
     kind: PathKind,
 }
@@ -29,18 +28,13 @@ pub enum PathKind {
 
 impl Path {
     pub fn new(path: Vec<Symbol>) -> Path {
-        Path::new_(path, None, Vec::new(), PathKind::Std)
+        Path::new_(path, Vec::new(), PathKind::Std)
     }
     pub fn new_local(path: Symbol) -> Path {
-        Path::new_(vec![path], None, Vec::new(), PathKind::Local)
+        Path::new_(vec![path], Vec::new(), PathKind::Local)
     }
-    pub fn new_(
-        path: Vec<Symbol>,
-        lifetime: Option<Ident>,
-        params: Vec<Box<Ty>>,
-        kind: PathKind,
-    ) -> Path {
-        Path { path, lifetime, params, kind }
+    pub fn new_(path: Vec<Symbol>, params: Vec<Box<Ty>>, kind: PathKind) -> Path {
+        Path { path, params, kind }
     }
 
     pub fn to_ty(
@@ -60,10 +54,8 @@ impl Path {
         self_generics: &Generics,
     ) -> ast::Path {
         let mut idents = self.path.iter().map(|s| Ident::new(*s, span)).collect();
-        let lt = mk_lifetimes(cx, span, &self.lifetime);
         let tys = self.params.iter().map(|t| t.to_ty(cx, span, self_ty, self_generics));
-        let params =
-            lt.into_iter().map(GenericArg::Lifetime).chain(tys.map(GenericArg::Type)).collect();
+        let params = tys.map(GenericArg::Type).collect();
 
         match self.kind {
             PathKind::Global => cx.path_all(span, true, idents, params),
@@ -98,14 +90,6 @@ pub fn nil_ty() -> Ty {
     Tuple(Vec::new())
 }
 
-fn mk_lifetime(cx: &ExtCtxt<'_>, span: Span, lt: &Option<Ident>) -> Option<ast::Lifetime> {
-    lt.map(|ident| cx.lifetime(span, ident))
-}
-
-fn mk_lifetimes(cx: &ExtCtxt<'_>, span: Span, lt: &Option<Ident>) -> Vec<ast::Lifetime> {
-    mk_lifetime(cx, span, lt).into_iter().collect()
-}
-
 impl Ty {
     pub fn to_ty(
         &self,

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -15,7 +15,7 @@ pub fn expand_deriving_hash(
     item: &Annotatable,
     push: &mut dyn FnMut(Annotatable),
 ) {
-    let path = Path::new_(pathvec_std!(hash::Hash), None, vec![], PathKind::Std);
+    let path = Path::new_(pathvec_std!(hash::Hash), vec![], PathKind::Std);
 
     let typaram = sym::__H;