From ed04824f1054a7eb65a7618cb5b844fa7065499b Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 23 Jan 2021 14:07:49 -0800
Subject: [PATCH] Move RenameRule parse from trait fn to associated

This will allow updating it to return an Err that borrows the input
string, which is not possible with FromStr.
---
 serde_derive/src/internals/attr.rs |  1 -
 serde_derive/src/internals/case.rs | 34 ++++++++++++------------------
 2 files changed, 14 insertions(+), 21 deletions(-)

diff --git a/serde_derive/src/internals/attr.rs b/serde_derive/src/internals/attr.rs
index 14e1625d..c2caf057 100644
--- a/serde_derive/src/internals/attr.rs
+++ b/serde_derive/src/internals/attr.rs
@@ -4,7 +4,6 @@ use proc_macro2::{Group, Span, TokenStream, TokenTree};
 use quote::ToTokens;
 use std::borrow::Cow;
 use std::collections::BTreeSet;
-use std::str::FromStr;
 use syn;
 use syn::parse::{self, Parse, ParseStream};
 use syn::punctuated::Punctuated;
diff --git a/serde_derive/src/internals/case.rs b/serde_derive/src/internals/case.rs
index 3fcbb32d..4e8a732d 100644
--- a/serde_derive/src/internals/case.rs
+++ b/serde_derive/src/internals/case.rs
@@ -5,8 +5,6 @@
 #[allow(deprecated, unused_imports)]
 use std::ascii::AsciiExt;
 
-use std::str::FromStr;
-
 use self::RenameRule::*;
 
 /// The different possible ways to change case of fields in a struct, or variants in an enum.
@@ -36,6 +34,20 @@ pub enum RenameRule {
 }
 
 impl RenameRule {
+    pub fn from_str(rename_all_str: &str) -> Result<Self, ()> {
+        match rename_all_str {
+            "lowercase" => Ok(LowerCase),
+            "UPPERCASE" => Ok(UPPERCASE),
+            "PascalCase" => Ok(PascalCase),
+            "camelCase" => Ok(CamelCase),
+            "snake_case" => Ok(SnakeCase),
+            "SCREAMING_SNAKE_CASE" => Ok(ScreamingSnakeCase),
+            "kebab-case" => Ok(KebabCase),
+            "SCREAMING-KEBAB-CASE" => Ok(ScreamingKebabCase),
+            _ => Err(()),
+        }
+    }
+
     /// Apply a renaming rule to an enum variant, returning the version expected in the source.
     pub fn apply_to_variant(&self, variant: &str) -> String {
         match *self {
@@ -92,24 +104,6 @@ impl RenameRule {
     }
 }
 
-impl FromStr for RenameRule {
-    type Err = ();
-
-    fn from_str(rename_all_str: &str) -> Result<Self, Self::Err> {
-        match rename_all_str {
-            "lowercase" => Ok(LowerCase),
-            "UPPERCASE" => Ok(UPPERCASE),
-            "PascalCase" => Ok(PascalCase),
-            "camelCase" => Ok(CamelCase),
-            "snake_case" => Ok(SnakeCase),
-            "SCREAMING_SNAKE_CASE" => Ok(ScreamingSnakeCase),
-            "kebab-case" => Ok(KebabCase),
-            "SCREAMING-KEBAB-CASE" => Ok(ScreamingKebabCase),
-            _ => Err(()),
-        }
-    }
-}
-
 #[test]
 fn rename_variants() {
     for &(original, lower, upper, camel, snake, screaming, kebab, screaming_kebab) in &[