From 12ee459903d50245570be8594e8aada4408e6139 Mon Sep 17 00:00:00 2001
From: David Kellum <dek-oss@gravitext.com>
Date: Thu, 18 Jul 2019 14:50:53 -0700
Subject: [PATCH 1/2] Add FutureProof variants to ParseError and
 SyntaxViolation

---
 src/parser.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/parser.rs b/src/parser.rs
index b65857f70..44f95b0f6 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -49,11 +49,17 @@ pub type ParseResult<T> = Result<T, ParseError>;
 macro_rules! simple_enum_error {
     ($($name: ident => $description: expr,)+) => {
         /// Errors that can occur during parsing.
+        ///
+        /// This may be extended in the future so exhaustive matching is
+        /// discouraged with an unused variant.
         #[derive(PartialEq, Eq, Clone, Copy, Debug)]
         pub enum ParseError {
             $(
                 $name,
             )+
+            /// Unused variant enable non-exhaustive matching
+            #[doc(hidden)]
+            __FutureProof,
         }
 
         impl Error for ParseError {
@@ -62,6 +68,9 @@ macro_rules! simple_enum_error {
                     $(
                         ParseError::$name => $description,
                     )+
+                    ParseError::__FutureProof => {
+                        unreachable!("Don't abuse the FutureProof!");
+                    }
                 }
             }
         }
@@ -96,11 +105,17 @@ impl From<::idna::Errors> for ParseError {
 macro_rules! syntax_violation_enum {
     ($($name: ident => $description: expr,)+) => {
         /// Non-fatal syntax violations that can occur during parsing.
+        ///
+        /// This may be extended in the future so exhaustive matching is
+        /// discouraged with an unused variant.
         #[derive(PartialEq, Eq, Clone, Copy, Debug)]
         pub enum SyntaxViolation {
             $(
                 $name,
             )+
+            /// Unused variant enable non-exhaustive matching
+            #[doc(hidden)]
+            __FutureProof,
         }
 
         impl SyntaxViolation {
@@ -109,6 +124,9 @@ macro_rules! syntax_violation_enum {
                     $(
                         SyntaxViolation::$name => $description,
                     )+
+                    SyntaxViolation::__FutureProof => {
+                        unreachable!("Don't abuse the FutureProof!");
+                    }
                 }
             }
         }

From 8cc477f5d3afee9ff8082fcee0139e54b11c89fc Mon Sep 17 00:00:00 2001
From: David Kellum <dek-oss@gravitext.com>
Date: Mon, 22 Jul 2019 09:23:31 -0700
Subject: [PATCH 2/2] Disambiguate Display::fmt calls for error types

---
 src/parser.rs | 8 ++++----
 tests/unit.rs | 1 +
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/parser.rs b/src/parser.rs
index 44f95b0f6..bf973659d 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -91,8 +91,8 @@ simple_enum_error! {
 }
 
 impl fmt::Display for ParseError {
-    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
-        self.description().fmt(fmt)
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        fmt::Display::fmt(self.description(), f)
     }
 }
 
@@ -151,8 +151,8 @@ syntax_violation_enum! {
 }
 
 impl fmt::Display for SyntaxViolation {
-    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
-        self.description().fmt(fmt)
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        fmt::Display::fmt(self.description(), f)
     }
 }
 
diff --git a/tests/unit.rs b/tests/unit.rs
index d5e81986a..9918ea316 100644
--- a/tests/unit.rs
+++ b/tests/unit.rs
@@ -512,6 +512,7 @@ fn test_syntax_violation_callback() {
     let v = violation.take().unwrap();
     assert_eq!(v, ExpectedDoubleSlash);
     assert_eq!(v.description(), "expected //");
+    assert_eq!(v.to_string(), "expected //");
 }
 
 #[test]