Use error-chain to create a crate-specific Error type

3 files changed, 14 insertions, 4 deletions

diff --git a/askama/Cargo.toml b/askama/Cargo.toml
index c9ee4ed..57708ee 100644
--- a/askama/Cargo.toml
+++ b/askama/Cargo.toml
@@ -17,3 +17,4 @@ travis-ci = { repository = "djc/askama" }
 
 [dependencies]
 askama_derive = { path = "../askama_derive", version = "0.3.4" }
+error-chain = "0.10"
diff --git a/askama/src/lib.rs b/askama/src/lib.rs
index 6f50c60..9c1d648 100644
--- a/askama/src/lib.rs
+++ b/askama/src/lib.rs
@@ -213,6 +213,8 @@
 #![allow(unused_imports)]
 #[macro_use]
 extern crate askama_derive;
+#[macro_use]
+extern crate error_chain;
 
 use std::env;
 use std::fmt;
@@ -232,10 +234,9 @@ pub trait Template {
     }
 }
 
-pub type Result<T> = std::result::Result<T, std::fmt::Error>;
-
 pub mod filters;
 pub use askama_derive::*;
+pub use errors::Result;
 
 // Duplicates askama_derive::path::template_dir()
 fn template_dir() -> PathBuf {
@@ -273,3 +274,11 @@ pub fn rerun_if_templates_changed() {
         println!("cargo:rerun-if-changed={}", e.path().to_str().unwrap());
     }).unwrap();
 }
+
+mod errors {
+    error_chain! {
+        foreign_links {
+            Fmt(::std::fmt::Error);
+        }
+    }
+}
diff --git a/askama_derive/src/generator.rs b/askama_derive/src/generator.rs
index 24d34cf..b00094d 100644
--- a/askama_derive/src/generator.rs
+++ b/askama_derive/src/generator.rs
@@ -481,8 +481,8 @@ impl<'a> Generator<'a> {
     // Implement `Display` for the given context struct.
     fn impl_display(&mut self, ast: &syn::DeriveInput) {
         self.write_header(ast, "::std::fmt::Display");
-        self.writeln("fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::askama::Result<()> {");
-        self.writeln("self.render_into(f)");
+        self.writeln("fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {");
+        self.writeln("self.render_into(f).map_err(|_| ::std::fmt::Error {})");
         self.writeln("}");
         self.writeln("}");
     }