[librsvg: 16/23] impl Error for AcceptLanguageError

[Federico Mena Quintero <federico src gnome org>]

commit 41edfce2e70a3868abb18b97a074d6d345c8df15
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri May 21 19:56:28 2021 -0500

    impl Error for AcceptLanguageError

 src/accept_language.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
---
diff --git a/src/accept_language.rs b/src/accept_language.rs
index b6e85c05..545dfea7 100644
--- a/src/accept_language.rs
+++ b/src/accept_language.rs
@@ -3,6 +3,8 @@
 use language_tags::{LanguageTag, ParseError};
 use locale_config::{LanguageRange, Locale};
 
+use std::error;
+use std::fmt;
 use std::str::FromStr;
 
 /// Used to set the language for rendering.
@@ -59,6 +61,19 @@ pub enum AcceptLanguageError {
     InvalidWeight,
 }
 
+impl error::Error for AcceptLanguageError {}
+
+impl fmt::Display for AcceptLanguageError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::NoElements => write!(f, "no language tags in list"),
+            Self::InvalidCharacters => write!(f, "invalid characters in language list"),
+            Self::InvalidLanguageTag(e) => write!(f, "invalid language tag: {}", e),
+            Self::InvalidWeight => write!(f, "invalid q= weight"),
+        }
+    }
+}
+
 /// Optional whitespace, Space or Tab, per https://datatracker.ietf.org/doc/html/rfc7230#section-3.2.3
 const OWS: [char; 2] = ['\x20', '\x09'];