Revert parts of "Use absolute paths in generated code"

to restore compatibility with older versions of Rust.

yaserde_derive/src/de/expand_enum.rs

@@ -161,7 +161,7 @@ fn build_unnamed_field_visitors(fields: &syn::FieldsUnnamed) -> TokenStream {
 
             fn #visitor(
               self,
-              v: &::std::primitive::str,
+              v: &str,
             ) -> ::std::result::Result<Self::Value, ::std::string::String> {
               #fn_body
             }

yaserde_derive/src/de/expand_struct.rs

@@ -82,7 +82,7 @@ pub fn parse(
 
             fn visit_str(
               self,
-              v: &::std::primitive::str,
+              v: &str,
             ) -> ::std::result::Result<Self::Value, ::std::string::String> {
               let content = "<".to_string() + #struct_id + ">" + v + "</" + #struct_id + ">";
               ::yaserde::de::from_str(&content)
@@ -114,7 +114,7 @@ pub fn parse(
 
             fn #visitor(
               self,
-              v: &::std::primitive::str,
+              v: &str,
             ) -> ::std::result::Result<Self::Value, ::std::string::String> {
               ::std::result::Result::Ok(#field_type::from_str(#map_if_bool).unwrap())
             }
@@ -363,7 +363,7 @@ pub fn parse(
           let event = reader.peek()?.to_owned();
           ::log::trace!(
             "Struct {} @ {}: matching {:?}",
-            ::std::stringify!(#name), start_depth, event,
+            stringify!(#name), start_depth, event,
           );
           match event {
             ::xml::reader::XmlEvent::StartElement{ref name, ref attributes, ..} => {

yaserde_derive/src/de/mod.rs

@@ -3,7 +3,7 @@ pub mod expand_enum;
 pub mod expand_struct;
 
 use crate::common::YaSerdeAttribute;
-use proc_macro2::TokenStream;
+use proc_macro2::{Ident, TokenStream};
 use quote::quote;
 
 pub fn expand_derive_deserialize(ast: &syn::DeriveInput) -> Result<TokenStream, String> {
@@ -29,9 +29,11 @@ pub fn expand_derive_deserialize(ast: &syn::DeriveInput) -> Result<TokenStream,
     syn::Data::Union(ref _data_union) => unimplemented!(),
   };
 
+  let dummy_const = Ident::new(&format!("_IMPL_YA_DESERIALIZE_FOR_{}", name), name.span());
+
   Ok(quote! {
     #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
-    const _: () = {
+    const #dummy_const: () = {
       use ::std::str::FromStr as _;
       use ::yaserde::Visitor as _;