Rollup merge of rust-lang#149350 - Jarcho:derive_recv_ctxt, r=jackh726

Mark method receivers in builtin derives as being from the derive.

Another small annoyance while working on clippy. This was clearly using the root context on purpose, but it also has no reason to do so. All the uses of the receiver are generated by the macros so they can just use the marked context rather than the root.

Author: tgross35

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

@@ -1052,7 +1052,7 @@ impl<'a> MethodDef<'a> {
 
         let args = {
             let self_arg = explicit_self.map(|explicit_self| {
-                let ident = Ident::with_dummy_span(kw::SelfLower).with_span_pos(span);
+                let ident = Ident::new(kw::SelfLower, span);
                 ast::Param::from_self(ast::AttrVec::default(), explicit_self, ident)
             });
             let nonself_args =

compiler/rustc_expand/src/build.rs

@@ -315,7 +315,7 @@ impl<'a> ExtCtxt<'a> {
         self.expr_path(self.path_ident(span, id))
     }
     pub fn expr_self(&self, span: Span) -> Box<ast::Expr> {
-        self.expr_ident(span, Ident::with_dummy_span(kw::SelfLower))
+        self.expr_ident(span, Ident::new(kw::SelfLower, span))
     }
 
     pub fn expr_macro_call(&self, span: Span, call: Box<ast::MacCall>) -> Box<ast::Expr> {