--- /dev/null
+#![deny(clippy::all, clippy::pedantic)]
+
+use std::error::Error as StdError;
+use std::io;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("implicit source")]
+pub struct ImplicitSource {
+ source: io::Error,
+}
+
+#[derive(Error, Debug)]
+#[error("explicit source")]
+pub struct ExplicitSource {
+ source: String,
+ #[source]
+ io: io::Error,
+}
+
+#[derive(Error, Debug)]
+#[error("boxed source")]
+pub struct BoxedSource {
+ #[source]
+ source: Box<dyn StdError + Send + 'static>,
+}
+
+#[test]
+fn test_implicit_source() {
+ let io = io::Error::new(io::ErrorKind::Other, "oh no!");
+ let error = ImplicitSource { source: io };
+ error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+#[test]
+fn test_explicit_source() {
+ let io = io::Error::new(io::ErrorKind::Other, "oh no!");
+ let error = ExplicitSource {
+ source: String::new(),
+ io,
+ };
+ error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+#[test]
+fn test_boxed_source() {
+ let source = Box::new(io::Error::new(io::ErrorKind::Other, "oh no!"));
+ let error = BoxedSource { source };
+ error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+macro_rules! error_from_macro {
+ ($($variants:tt)*) => {
+ #[derive(Error)]
+ #[derive(Debug)]
+ pub enum MacroSource {
+ $($variants)*
+ }
+ }
+}
+
+// Test that we generate impls with the proper hygiene
+error_from_macro!(#[error("Something")] Variant(#[from] io::Error));