1 files changed, 89 insertions, 0 deletions
diff --git a/derive-macro/src/spanned.rs b/derive-macro/src/spanned.rs
new file mode 100644
index 00000000..339a654e
--- /dev/null
+++ b/derive-macro/src/spanned.rs
@@ -0,0 +1,89 @@
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::ToTokens;
+use syn::LitStr;
+
+use std::ops::{Deref, DerefMut};
+
+/// An entity with a span attached.
+#[derive(Debug, Copy, Clone)]
+pub struct Sp<T> {
+    val: T,
+    span: Span,
+}
+
+impl<T> Sp<T> {
+    pub fn new(val: T, span: Span) -> Self {
+        Sp { val, span }
+    }
+
+    pub fn get(&self) -> &T {
+        &self.val
+    }
+
+    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<U, T: PartialEq<U>> PartialEq<U> for Sp<T> {
+    fn eq(&self, other: &U) -> 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 could come up with
+        let tt = self.val.to_token_stream().into_iter().map(|mut tt| {
+            tt.set_span(self.span);
+            tt
+        });
+
+        stream.extend(tt);
+    }
+}