1 files changed, 78 insertions, 0 deletions
diff --git a/third_party/rust/thiserror/tests/test_transparent.rs b/third_party/rust/thiserror/tests/test_transparent.rs
new file mode 100644
index 0000000000..6f3c03ec7a
--- /dev/null
+++ b/third_party/rust/thiserror/tests/test_transparent.rs
@@ -0,0 +1,78 @@
+use anyhow::anyhow;
+use std::error::Error as _;
+use std::io;
+use thiserror::Error;
+
+#[test]
+fn test_transparent_struct() {
+    #[derive(Error, Debug)]
+    #[error(transparent)]
+    struct Error(ErrorKind);
+
+    #[derive(Error, Debug)]
+    enum ErrorKind {
+        #[error("E0")]
+        E0,
+        #[error("E1")]
+        E1(#[from] io::Error),
+    }
+
+    let error = Error(ErrorKind::E0);
+    assert_eq!("E0", error.to_string());
+    assert!(error.source().is_none());
+
+    let io = io::Error::new(io::ErrorKind::Other, "oh no!");
+    let error = Error(ErrorKind::from(io));
+    assert_eq!("E1", error.to_string());
+    error.source().unwrap().downcast_ref::<io::Error>().unwrap();
+}
+
+#[test]
+fn test_transparent_enum() {
+    #[derive(Error, Debug)]
+    enum Error {
+        #[error("this failed")]
+        This,
+        #[error(transparent)]
+        Other(anyhow::Error),
+    }
+
+    let error = Error::This;
+    assert_eq!("this failed", error.to_string());
+
+    let error = Error::Other(anyhow!("inner").context("outer"));
+    assert_eq!("outer", error.to_string());
+    assert_eq!("inner", error.source().unwrap().to_string());
+}
+
+#[test]
+fn test_anyhow() {
+    #[derive(Error, Debug)]
+    #[error(transparent)]
+    struct Any(#[from] anyhow::Error);
+
+    let error = Any::from(anyhow!("inner").context("outer"));
+    assert_eq!("outer", error.to_string());
+    assert_eq!("inner", error.source().unwrap().to_string());
+}
+
+#[test]
+fn test_non_static() {
+    #[derive(Error, Debug)]
+    #[error(transparent)]
+    struct Error<'a> {
+        inner: ErrorKind<'a>,
+    }
+
+    #[derive(Error, Debug)]
+    enum ErrorKind<'a> {
+        #[error("unexpected token: {:?}", token)]
+        Unexpected { token: &'a str },
+    }
+
+    let error = Error {
+        inner: ErrorKind::Unexpected { token: "error" },
+    };
+    assert_eq!("unexpected token: \"error\"", error.to_string());
+    assert!(error.source().is_none());
+}