From 7db0982e582399f1ffaa5128fc7a71d4764d9998 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 23 Jan 2021 14:09:58 -0800
Subject: [PATCH] Add error type to use for RenameRule parsing

---
 serde_derive/src/internals/attr.rs | 12 ++++++------
 serde_derive/src/internals/case.rs |  8 ++++++--
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/serde_derive/src/internals/attr.rs b/serde_derive/src/internals/attr.rs
index c2caf057..cea79663 100644
--- a/serde_derive/src/internals/attr.rs
+++ b/serde_derive/src/internals/attr.rs
@@ -339,7 +339,7 @@ impl Container {
                                 rename_all_ser_rule.set(&m.path, rename_rule);
                                 rename_all_de_rule.set(&m.path, rename_rule);
                             }
-                            Err(()) => cx.error_spanned_by(
+                            Err(_err) => cx.error_spanned_by(
                                 s,
                                 format!(
                                     "unknown rename rule for #[serde(rename_all = {:?})]",
@@ -356,7 +356,7 @@ impl Container {
                         if let Some(ser) = ser {
                             match RenameRule::from_str(&ser.value()) {
                                 Ok(rename_rule) => rename_all_ser_rule.set(&m.path, rename_rule),
-                                Err(()) => cx.error_spanned_by(
+                                Err(_err) => cx.error_spanned_by(
                                     ser,
                                     format!(
                                         "unknown rename rule for #[serde(rename_all = {:?})]",
@@ -368,7 +368,7 @@ impl Container {
                         if let Some(de) = de {
                             match RenameRule::from_str(&de.value()) {
                                 Ok(rename_rule) => rename_all_de_rule.set(&m.path, rename_rule),
-                                Err(()) => cx.error_spanned_by(
+                                Err(_err) => cx.error_spanned_by(
                                     de,
                                     format!(
                                         "unknown rename rule for #[serde(rename_all = {:?})]",
@@ -930,7 +930,7 @@ impl Variant {
                                 rename_all_ser_rule.set(&m.path, rename_rule);
                                 rename_all_de_rule.set(&m.path, rename_rule);
                             }
-                            Err(()) => cx.error_spanned_by(
+                            Err(_err) => cx.error_spanned_by(
                                 s,
                                 format!(
                                     "unknown rename rule for #[serde(rename_all = {:?})]",
@@ -947,7 +947,7 @@ impl Variant {
                         if let Some(ser) = ser {
                             match RenameRule::from_str(&ser.value()) {
                                 Ok(rename_rule) => rename_all_ser_rule.set(&m.path, rename_rule),
-                                Err(()) => cx.error_spanned_by(
+                                Err(_err) => cx.error_spanned_by(
                                     ser,
                                     format!(
                                         "unknown rename rule for #[serde(rename_all = {:?})]",
@@ -959,7 +959,7 @@ impl Variant {
                         if let Some(de) = de {
                             match RenameRule::from_str(&de.value()) {
                                 Ok(rename_rule) => rename_all_de_rule.set(&m.path, rename_rule),
-                                Err(()) => cx.error_spanned_by(
+                                Err(_err) => cx.error_spanned_by(
                                     de,
                                     format!(
                                         "unknown rename rule for #[serde(rename_all = {:?})]",
diff --git a/serde_derive/src/internals/case.rs b/serde_derive/src/internals/case.rs
index 4e8a732d..d9634e73 100644
--- a/serde_derive/src/internals/case.rs
+++ b/serde_derive/src/internals/case.rs
@@ -34,7 +34,7 @@ pub enum RenameRule {
 }
 
 impl RenameRule {
-    pub fn from_str(rename_all_str: &str) -> Result<Self, ()> {
+    pub fn from_str(rename_all_str: &str) -> Result<Self, ParseError> {
         match rename_all_str {
             "lowercase" => Ok(LowerCase),
             "UPPERCASE" => Ok(UPPERCASE),
@@ -44,7 +44,7 @@ impl RenameRule {
             "SCREAMING_SNAKE_CASE" => Ok(ScreamingSnakeCase),
             "kebab-case" => Ok(KebabCase),
             "SCREAMING-KEBAB-CASE" => Ok(ScreamingKebabCase),
-            _ => Err(()),
+            unknown => Err(ParseError { unknown }),
         }
     }
 
@@ -104,6 +104,10 @@ impl RenameRule {
     }
 }
 
+pub struct ParseError<'a> {
+    unknown: &'a str,
+}
+
 #[test]
 fn rename_variants() {
     for &(original, lower, upper, camel, snake, screaming, kebab, screaming_kebab) in &[