From 65acbb2d61283df4ff9149991abdc52638f8995d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Agust=C3=ADn=20Borgna?= <agustin.borgna@quantinuum.com>
Date: Mon, 21 Oct 2024 13:21:34 +0100
Subject: [PATCH] workaround a derive_more linting error

---
 hugr-core/src/package.rs   | 36 +++++++++++++++++++++++++++++++++---
 release-please-config.json |  2 +-
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/hugr-core/src/package.rs b/hugr-core/src/package.rs
index b1a722b7e..586d31c3e 100644
--- a/hugr-core/src/package.rs
+++ b/hugr-core/src/package.rs
@@ -275,7 +275,7 @@ pub enum PackageEncodingError {
 }
 
 /// Error raised while validating a package.
-#[derive(Debug, Display, Error, From)]
+#[derive(Debug, From)]
 #[non_exhaustive]
 pub enum PackageValidationError {
     /// Error raised while processing the package extensions.
@@ -283,21 +283,51 @@ pub enum PackageValidationError {
     /// Error raised while validating the package hugrs.
     Validation(ValidationError),
     /// Error validating HUGR.
+    // TODO: Remove manual Display and Error impls when removing deprecated variants.
+    #[from(ignore)]
     #[deprecated(
         since = "0.13.2",
         note = "Replaced by `PackageValidationError::Validation`"
     )]
-    #[from(ignore)]
     Validate(ValidationError),
     /// Error registering extension.
+    // TODO: Remove manual Display and Error impls when removing deprecated variants.
+    #[from(ignore)]
     #[deprecated(
         since = "0.13.2",
         note = "Replaced by `PackageValidationError::Extension`"
     )]
-    #[from(ignore)]
     ExtReg(ExtensionRegistryError),
 }
 
+// Note: We cannot use the `derive_more::Error` derive due to a bug with deprecated elements.
+// See https://github.com/JelteF/derive_more/issues/419
+#[allow(deprecated)]
+impl std::error::Error for PackageValidationError {
+    fn source(&self) -> Option<&(dyn derive_more::Error + 'static)> {
+        match self {
+            PackageValidationError::Extension(source) => Some(source),
+            PackageValidationError::Validation(source) => Some(source),
+            PackageValidationError::Validate(source) => Some(source),
+            PackageValidationError::ExtReg(source) => Some(source),
+        }
+    }
+}
+
+// Note: We cannot use the `derive_more::Display` derive due to a bug with deprecated elements.
+// See https://github.com/JelteF/derive_more/issues/419
+impl Display for PackageValidationError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        #[allow(deprecated)]
+        match self {
+            PackageValidationError::Extension(e) => write!(f, "Error processing extensions: {}", e),
+            PackageValidationError::Validation(e) => write!(f, "Error validating HUGR: {}", e),
+            PackageValidationError::Validate(e) => write!(f, "Error validating HUGR: {}", e),
+            PackageValidationError::ExtReg(e) => write!(f, "Error registering extension: {}", e),
+        }
+    }
+}
+
 #[cfg(test)]
 mod test {
     use cool_asserts::assert_matches;
diff --git a/release-please-config.json b/release-please-config.json
index 54e6bdf7b..7cbb53196 100644
--- a/release-please-config.json
+++ b/release-please-config.json
@@ -63,4 +63,4 @@
             "hidden": true
         }
     ]
-}
\ No newline at end of file
+}