From 6f6c1b3cf0eb54923fa22328e79f03e42b1839a2 Mon Sep 17 00:00:00 2001
From: Varun Chawla <varun_6april@hotmail.com>
Date: Fri, 13 Feb 2026 00:50:10 -0800
Subject: [PATCH] Fix documentation example for transparent error pattern

The example showing how to use #[error(transparent)] with #[from] on a
struct wrapping an enum had a placeholder (...) that didn't compile when
users tried to complete it.

Added a concrete example showing:
- A variant in ErrorRepr with #[from] attribute
- Helper code demonstrating the From trait chain works correctly
- A working example function that uses the ? operator

The key insight is that functions need to return Result<(), ErrorRepr>
for the From chain to work: InvalidInputError -> ErrorRepr -> PublicError

Fixes #439
---
 README.md  |  4 +++-
 src/lib.rs | 18 +++++++++++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 7c67cb2..60fbef0 100644
--- a/README.md
+++ b/README.md
@@ -197,7 +197,9 @@ pub enum DataStoreError {
   // Private and free to change across minor version of the crate.
   #[derive(Error, Debug)]
   enum ErrorRepr {
-      ...
+      #[error("invalid input")]
+      InvalidInput(#[from] InvalidInputError),
+      // Additional error variants can be added here
   }
   ```
 
diff --git a/src/lib.rs b/src/lib.rs
index c26aa0c..fae9b80 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -245,10 +245,22 @@
 //!   // Private and free to change across minor version of the crate.
 //!   #[derive(Error, Debug)]
 //!   enum ErrorRepr {
-//!       # /*
-//!       ...
-//!       # */
+//!       #[error("invalid input")]
+//!       InvalidInput(#[from] InvalidInputError),
 //!   }
+//!   #
+//!   # #[derive(Error, Debug)]
+//!   # #[error("invalid input")]
+//!   # struct InvalidInputError;
+//!   #
+//!   # fn process() -> Result<(), ErrorRepr> {
+//!   #     Err(InvalidInputError.into())
+//!   # }
+//!   #
+//!   # fn example() -> Result<(), PublicError> {
+//!   #     process()?;
+//!   #     Ok(())
+//!   # }
 //!   ```
 //!
 //! - See also the [`anyhow`] library for a convenient single error type to use