[librsvg: 15/32] impl Display for DefsLookupErrorKind

[Federico Mena Quintero <federico src gnome org>]

commit 7e50c99b2c09c7f18a0ad63d4923afdd9deb2ff1
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Nov 26 13:20:37 2020 -0600

    impl Display for DefsLookupErrorKind
    
    In preparation for not exposing this enum to the public API, we'll
    have a way to print it.

 src/error.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)
---
diff --git a/src/error.rs b/src/error.rs
index 4a8a6da2..a1957b29 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -116,6 +116,18 @@ pub enum DefsLookupErrorKind {
     NotFound,
 }
 
+impl fmt::Display for DefsLookupErrorKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match *self {
+            DefsLookupErrorKind::HrefError(_) => write!(f, "invalid URL"),
+            DefsLookupErrorKind::CannotLookupExternalReferences => {
+                write!(f, "cannot lookup references to elements in external files")
+            }
+            DefsLookupErrorKind::NotFound => write!(f, "not found"),
+        }
+    }
+}
+
 /// Errors that can happen while rendering or measuring an SVG document.
 #[non_exhaustive]
 #[derive(Debug, Clone, PartialEq)]