--- /dev/null
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::ToTokens;
+use std::ops::{Deref, DerefMut};
+use syn::LitStr;
+
+/// An entity with a span attached.
+#[derive(Debug, Clone)]
+pub struct Sp<T> {
+ span: Span,
+ val: T,
+}
+
+impl<T> Sp<T> {
+ pub fn new(val: T, span: Span) -> Self {
+ Sp { val, span }
+ }
+
+ pub fn call_site(val: T) -> Self {
+ Sp {
+ val,
+ span: Span::call_site(),
+ }
+ }
+
+ pub fn span(&self) -> Span {
+ self.span
+ }
+}
+
+impl<T> Deref for Sp<T> {
+ type Target = T;
+
+ fn deref(&self) -> &T {
+ &self.val
+ }
+}
+
+impl<T> DerefMut for Sp<T> {
+ fn deref_mut(&mut self) -> &mut T {
+ &mut self.val
+ }
+}
+
+impl From<Ident> for Sp<String> {
+ fn from(ident: Ident) -> Self {
+ Sp {
+ val: ident.to_string(),
+ span: ident.span(),
+ }
+ }
+}
+
+impl From<LitStr> for Sp<String> {
+ fn from(lit: LitStr) -> Self {
+ Sp {
+ val: lit.value(),
+ span: lit.span(),
+ }
+ }
+}
+
+impl<'a> From<Sp<&'a str>> for Sp<String> {
+ fn from(sp: Sp<&'a str>) -> Self {
+ Sp::new(sp.val.into(), sp.span)
+ }
+}
+
+impl<T: PartialEq> PartialEq<T> for Sp<T> {
+ fn eq(&self, other: &T) -> bool {
+ self.val == *other
+ }
+}
+
+impl<T: PartialEq> PartialEq for Sp<T> {
+ fn eq(&self, other: &Sp<T>) -> bool {
+ self.val == **other
+ }
+}
+
+impl<T: AsRef<str>> AsRef<str> for Sp<T> {
+ fn as_ref(&self) -> &str {
+ self.val.as_ref()
+ }
+}
+
+impl<T: ToTokens> ToTokens for Sp<T> {
+ fn to_tokens(&self, stream: &mut TokenStream) {
+ // this is the simplest way out of correct ones to change span on
+ // arbitrary token tree I can come up with
+ let tt = self.val.to_token_stream().into_iter().map(|mut tt| {
+ tt.set_span(self.span);
+ tt
+ });
+
+ stream.extend(tt);
+ }
+}