From 1dfdc001b34a6555f161f0526f8ba21ac8e9c3c7 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Sat, 13 May 2017 15:26:41 -0700
Subject: [PATCH] Add an error class

---
 lexer/src/error.rs | 16 ++++++++++++++++
 lexer/src/lib.rs   | 12 ++++++++----
 2 files changed, 24 insertions(+), 4 deletions(-)
 create mode 100644 lexer/src/error.rs

diff --git a/lexer/src/error.rs b/lexer/src/error.rs
new file mode 100644
index 0000000..93aa3d2
--- /dev/null
+++ b/lexer/src/error.rs
@@ -0,0 +1,16 @@
+/* lexer/src/error.rs
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+#[derive(Debug, Eq, PartialEq)]
+pub struct Error {
+    message: String
+}
+
+impl Error {
+    pub fn new(msg: String) -> Error {
+        Error {
+            message: msg
+        }
+    }
+}
diff --git a/lexer/src/lib.rs b/lexer/src/lib.rs
index f7ad002..e01c242 100644
--- a/lexer/src/lib.rs
+++ b/lexer/src/lib.rs
@@ -4,6 +4,10 @@
 
 use std::iter::Peekable;
 
+mod error;
+
+pub use error::Error;
+
 #[derive(Debug, Eq, PartialEq)]
 pub enum Token { LeftParen, RightParen, Id(String), }
 
@@ -15,7 +19,7 @@ enum IterationResult {
     Finish,
     Continue,
     Emit(Token, Resume),
-    Error(String),
+    Error(Error),
 }
 
 pub struct Lexer<T> where T: Iterator<Item=char> {
@@ -32,12 +36,12 @@ impl<T> Lexer<T> where T: Iterator<Item=char> {
     }
 
     fn fail(&self, msg: String) -> IterationResult {
-        IterationResult::Error(msg)
+        IterationResult::Error(Error::new(msg))
     }
 }
 
 impl<T> Iterator for Lexer<T> where T: Iterator<Item=char> {
-    type Item = Result<Token, String>;
+    type Item = Result<Token, Error>;
 
     fn next(&mut self) -> Option<Self::Item> {
         let mut buffer = String::new();
@@ -81,7 +85,7 @@ impl<T> Iterator for Lexer<T> where T: Iterator<Item=char> {
                     }
                     return Some(Ok(token))
                 },
-                IterationResult::Error(msg) => return Some(Err(msg)),
+                IterationResult::Error(err) => return Some(Err(err)),
             };
         }
         None