1 files changed, 22 insertions, 0 deletions
diff --git a/src/utils/error.rs b/src/utils/error.rs
new file mode 100644
index 0000000..276e349
--- /dev/null
+++ b/src/utils/error.rs
@@ -0,0 +1,22 @@
+pub trait SpanError {
+    #[allow(non_snake_case)]
+    fn EXPECTED_Span_OR_ToTokens<D: std::fmt::Display>(&self, msg: D) -> syn::Error;
+}
+
+pub trait ToTokensError {
+    #[allow(non_snake_case)]
+    fn EXPECTED_Span_OR_ToTokens<D: std::fmt::Display>(&self, msg: D) -> syn::Error;
+}
+
+impl<T: quote::ToTokens> ToTokensError for T {
+    fn EXPECTED_Span_OR_ToTokens<D: std::fmt::Display>(&self, msg: D) -> syn::Error {
+        // Curb monomorphization from generating too many identical `new_spanned`.
+        syn::Error::new_spanned(self.to_token_stream(), msg)
+    }
+}
+
+impl SpanError for proc_macro2::Span {
+    fn EXPECTED_Span_OR_ToTokens<D: std::fmt::Display>(&self, msg: D) -> syn::Error {
+        syn::Error::new(*self, msg)
+    }
+}