Add test for displaying paths

Cargo.toml

@@ -15,6 +15,7 @@ thiserror-impl = { version = "=1.0.4", path = "impl" }
 
 [dev-dependencies]
 anyhow = "1.0"
+ref-cast = "1.0"
 rustversion = "1.0"
 trybuild = "1.0"
 

tests/test_path.rs

@@ -0,0 +1,37 @@
+use ref_cast::RefCast;
+use std::fmt::Display;
+use std::path::{Path, PathBuf};
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("failed to read '{file}'")]
+struct StructPathBuf {
+    file: PathBuf,
+}
+
+#[derive(Error, Debug, RefCast)]
+#[repr(C)]
+#[error("failed to read '{file}'")]
+struct StructPath {
+    file: Path,
+}
+
+#[derive(Error, Debug)]
+enum EnumPathBuf {
+    #[error("failed to read '{0}'")]
+    Read(PathBuf),
+}
+
+fn assert<T: Display>(expected: &str, value: T) {
+    assert_eq!(expected, value.to_string());
+}
+
+#[test]
+fn test_display() {
+    let path = Path::new("/thiserror");
+    let file = path.to_owned();
+    assert("failed to read '/thiserror'", StructPathBuf { file });
+    let file = path.to_owned();
+    assert("failed to read '/thiserror'", EnumPathBuf::Read(file));
+    assert("failed to read '/thiserror'", StructPath::ref_cast(path));
+}