Seal the private api Spanned trait

dtolnay · Mar 12, 2023 · cd7c205 · cd7c205
1 parent d8551a9
commit cd7c205
Showing 1 changed file with 12 additions and 1 deletion.
diff --git a/src/spanned.rs b/src/spanned.rs
@@ -2,7 +2,7 @@ use crate::ToTokens;
 use proc_macro2::extra::DelimSpan;
 use proc_macro2::{Span, TokenStream};
 
-pub trait Spanned {
+pub trait Spanned: private::Sealed {
     fn __span(&self) -> Span;
 }
 
@@ -48,3 +48,14 @@ fn join_spans(tokens: TokenStream) -> Span {
         .and_then(|last| first.join(last))
         .unwrap_or(first)
 }
+
+mod private {
+    use crate::ToTokens;
+    use proc_macro2::extra::DelimSpan;
+    use proc_macro2::Span;
+
+    pub trait Sealed {}
+    impl Sealed for Span {}
+    impl Sealed for DelimSpan {}
+    impl<T: ?Sized + ToTokens> Sealed for T {}
+}