Switch from error_core to failure.

lib/filecheck/src/error.rs

@@ -1,21 +1,21 @@
 use std::result;
 use std::convert::From;
-use std::error::Error as StdError;
-use std::fmt;
 use regex;
 
 /// A result from the filecheck library.
 pub type Result<T> = result::Result<T, Error>;
 
 /// A filecheck error.
-#[derive(Debug)]
+#[derive(Fail, Debug)]
 pub enum Error {
     /// A syntax error in a check line.
+    #[fail(display = "{}", _0)]
     Syntax(String),
     /// A check refers to an undefined variable.
     ///
     /// The pattern contains `$foo` where the `foo` variable has not yet been defined.
     /// Use `$$` to match a literal dollar sign.
+    #[fail(display = "{}", _0)]
     UndefVariable(String),
     /// A pattern contains a back-reference to a variable that was defined in the same pattern.
     ///
@@ -26,40 +26,19 @@ pub enum Error {
     /// check: Hello $(world=[^ ]*)
     /// sameln: $world
     /// ```
+    #[fail(display = "{}", _0)]
     Backref(String),
     /// A pattern contains multiple definitions of the same variable.
+    #[fail(display = "{}", _0)]
     DuplicateDef(String),
     /// An error in a regular expression.
     ///
     /// Use `cause()` to get the underlying `Regex` library error.
-    Regex(regex::Error),
-}
-
-impl StdError for Error {
-    fn description(&self) -> &str {
-        use Error::*;
-        match *self {
-            Syntax(ref s) |
-            UndefVariable(ref s) |
-            Backref(ref s) |
-            DuplicateDef(ref s) => s,
-            Regex(ref err) => err.description(),
-        }
-    }
-
-    fn cause(&self) -> Option<&StdError> {
-        use Error::*;
-        match *self {
-            Regex(ref err) => Some(err),
-            _ => None,
-        }
-    }
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{}", self.description())
-    }
+    #[fail(display = "{}", _0)]
+    Regex(
+        #[cause]
+        regex::Error
+    ),
 }
 
 impl From<regex::Error> for Error {

lib/filecheck/src/lib.rs

@@ -243,6 +243,9 @@ pub use variable::{VariableMap, Value, NO_VARIABLES};
 pub use checker::{Checker, CheckerBuilder};
 
 extern crate regex;
+extern crate failure;
+#[macro_use]
+extern crate failure_derive;
 
 mod error;
 mod variable;