hir: remove NodeId from Arg

src/librustc/hir/lowering.rs

@@ -2042,9 +2042,8 @@ impl<'a> LoweringContext<'a> {
     }
 
     fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
-        let LoweredNodeId { node_id, hir_id } = self.lower_node_id(arg.id);
+        let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(arg.id);
         hir::Arg {
-            id: node_id,
             hir_id,
             pat: self.lower_pat(&arg.pat),
         }

src/librustc/hir/mod.rs

@@ -1852,7 +1852,6 @@ pub struct InlineAsm {
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Arg {
     pub pat: P<Pat>,
-    pub id: NodeId,
     pub hir_id: HirId,
 }
 

src/librustc/ich/impls_hir.rs

@@ -955,7 +955,6 @@ impl_stable_hash_for!(enum hir::StmtKind {
 
 impl_stable_hash_for!(struct hir::Arg {
     pat,
-    id,
     hir_id
 });