Add a partial ordering on severity

codespan-reporting/src/lib.rs

@@ -1,6 +1,7 @@
 extern crate codespan;
 extern crate termcolor;
 
+use std::cmp::Ordering;
 use std::fmt;
 use termcolor::Color;
 
@@ -11,7 +12,18 @@ pub use self::diagnostic::{Diagnostic, Label, LabelStyle};
 pub use self::emitter::emit;
 
 /// A severity level for diagnostic messages
-#[derive(Copy, PartialEq, Clone, Hash, Debug)]
+///
+/// These are ordered in the following way:
+///
+/// ```rust
+/// use codespan_reporting::Severity;
+///
+/// assert!(Severity::Bug > Severity::Error);
+/// assert!(Severity::Error > Severity::Warning);
+/// assert!(Severity::Warning > Severity::Note);
+/// assert!(Severity::Note > Severity::Help);
+/// ```
+#[derive(Copy, Clone, PartialEq, Hash, Debug)]
 pub enum Severity {
     /// An unexpected bug.
     Bug,
@@ -25,6 +37,25 @@ pub enum Severity {
     Help,
 }
 
+impl Severity {
+    /// We want bugs to be the maximum severity, errors next, etc...
+    fn to_cmp_int(self) -> u8 {
+        match self {
+            Severity::Bug => 5,
+            Severity::Error => 4,
+            Severity::Warning => 3,
+            Severity::Note => 2,
+            Severity::Help => 1,
+        }
+    }
+}
+
+impl PartialOrd for Severity {
+    fn partial_cmp(&self, other: &Severity) -> Option<Ordering> {
+        u8::partial_cmp(&self.to_cmp_int(), &other.to_cmp_int())
+    }
+}
+
 impl fmt::Display for Severity {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.to_str().fmt(f)