feat(protocol): Simplify protocol return values further

BREAKING CHANGE: Switched to Box instead of & for help/code return values.

src/protocol.rs

@@ -18,7 +18,7 @@ pub trait Diagnostic: std::error::Error {
     /// the toplevel crate's documentation for easy searching. Rust path
     /// format (`foo::bar::baz`) is recommended, but more classic codes like
     /// `E0123` or Enums will work just fine.
-    fn code(&self) -> &(dyn Display);
+    fn code<'a>(&'a self) -> Box<dyn Display + 'a>;
 
     /// Diagnostic severity. This may be used by [DiagnosticReporter]s to change the
     /// display format of this diagnostic.
@@ -30,7 +30,7 @@ pub trait Diagnostic: std::error::Error {
 
     /// Additional help text related to this Diagnostic. Do you have any
     /// advice for the poor soul who's just run into this issue?
-    fn help(&self) -> Option<&(dyn Display)> {
+    fn help<'a>(&'a self) -> Option<Box<dyn Display + 'a>> {
         None
     }
 

src/reporter.rs

@@ -163,7 +163,9 @@ impl DiagnosticReporter for JokeReporter {
             "me, with {} {}: {}",
             sev,
             diagnostic,
-            diagnostic.help().unwrap_or(&"have you tried not failing?")
+            diagnostic
+                .help()
+                .unwrap_or_else(|| Box::new(&"have you tried not failing?"))
         )?;
         writeln!(
             f,

tests/reporter.rs

@@ -18,12 +18,12 @@ impl fmt::Debug for MyBad {
 }
 
 impl Diagnostic for MyBad {
-    fn code(&self) -> &(dyn std::fmt::Display) {
+    fn code(&self) -> Box<dyn std::fmt::Display> {
-        &"oops::my::bad"
+        Box::new(&"oops::my::bad")
     }
 
-    fn help(&self) -> Option<&(dyn std::fmt::Display)> {
+    fn help(&self) -> Option<Box<dyn std::fmt::Display>> {
-        Some(&"try doing it better next time?")
+        Some(Box::new(&"try doing it better next time?"))
     }
 
     fn snippets(&self) -> Option<Box<dyn Iterator<Item = DiagnosticSnippet>>> {