From 316c8f1aea3c886067ad285f217da77213757927 Mon Sep 17 00:00:00 2001
From: Anders429 <anders.stefan.evensen@gmail.com>
Date: Tue, 7 Oct 2025 10:49:16 -0600
Subject: [PATCH] Propagate lower-level errors as sources.

---
 embedded-io/src/lib.rs | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/embedded-io/src/lib.rs b/embedded-io/src/lib.rs
index 0918cdb5..96bf9e18 100644
--- a/embedded-io/src/lib.rs
+++ b/embedded-io/src/lib.rs
@@ -261,7 +261,14 @@ impl<E: fmt::Debug> fmt::Display for ReadExactError<E> {
     }
 }
 
-impl<E: fmt::Debug> core::error::Error for ReadExactError<E> {}
+impl<E: core::error::Error + 'static> core::error::Error for ReadExactError<E> {
+    fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
+        match self {
+            Self::UnexpectedEof => None,
+            Self::Other(error) => Some(error),
+        }
+    }
+}
 
 /// Errors that could be returned by `Write` on `&mut [u8]`.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
@@ -294,7 +301,14 @@ impl<E: fmt::Debug> fmt::Display for WriteFmtError<E> {
     }
 }
 
-impl<E: fmt::Debug> core::error::Error for WriteFmtError<E> {}
+impl<E: core::error::Error + 'static> core::error::Error for WriteFmtError<E> {
+    fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
+        match self {
+            Self::FmtError => None,
+            Self::Other(error) => Some(error),
+        }
+    }
+}
 
 /// Blocking reader.
 ///