refactor: add ErrorExt

examples/src/custom-layout.rs

@@ -45,7 +45,7 @@ impl std::fmt::Display for MainError {
     }
 }
 
-impl std::error::Error for MainError {}
+impl Error for MainError {}
 
 impl MainError {
     /// Convert an `Exn<E>` into MainError with custom numbered list formatting.
@@ -92,7 +92,7 @@ mod app {
         }
     }
 
-    impl std::error::Error for AppError {}
+    impl Error for AppError {}
 }
 
 mod http {
@@ -115,7 +115,7 @@ mod http {
         }
     }
 
-    impl std::error::Error for HttpError {}
+    impl Error for HttpError {}
 }
 
 // Output when running `cargo run --example custom_layout`:

examples/src/downcast.rs

@@ -73,7 +73,7 @@ fn extract_http_status<E: Error + Send + Sync>(err: &Exn<E>) -> Option<u16> {
 #[derive(Debug, Display)]
 #[display("fatal error occurred in application")]
 struct MainError;
-impl std::error::Error for MainError {}
+impl Error for MainError {}
 
 mod app {
     use super::*;
@@ -85,7 +85,7 @@ mod app {
 
     #[derive(Debug, Display)]
     pub struct AppError(String);
-    impl std::error::Error for AppError {}
+    impl Error for AppError {}
 }
 
 mod http {
@@ -104,7 +104,7 @@ mod http {
         pub status: u16,
         pub message: String,
     }
-    impl std::error::Error for HttpError {}
+    impl Error for HttpError {}
 }
 
 // Output when running `cargo run --example downcast`:

exn/src/ext.rs

@@ -0,0 +1,53 @@
+// Copyright 2025 FastLabs Developers
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::error::Error;
+
+use crate::Exn;
+use crate::Result;
+
+/// Equivalent to `Ok::<_, Exn<E>>(value)`.
+///
+/// This simplifies creation of an `exn::Result` in places where type inference cannot deduce the
+/// `E` type of the result &mdash; without needing to write `Ok::<_, Exn<E>>(value)`.
+///
+/// One might think that `exn::Result::Ok(value)` would work in such cases, but it does not.
+///
+/// ```console
+/// error[E0282]: type annotations needed for `std::result::Result<i32, E>`
+///   --> src/main.rs:11:13
+///    |
+/// 11 |     let _ = exn::Result::Ok(1);
+///    |         -   ^^^^^^^^^^^^^^^ cannot infer type for type parameter `E` declared on the enum `Result`
+///    |         |
+///    |         consider giving this pattern the explicit type `std::result::Result<i32, E>`, where the type parameter `E` is specified
+/// ```
+#[expect(non_snake_case)]
+pub fn Ok<T, E: Error + Send + Sync + 'static>(value: T) -> Result<T, E> {
+    Result::Ok(value)
+}
+
+/// An extension trait for error types to raise them as exceptions.
+pub trait ErrorExt: Error + Send + Sync + 'static {
+    /// Raise this error as a new exception.
+    #[track_caller]
+    fn raise(self) -> Exn<Self>
+    where
+        Self: Sized,
+    {
+        Exn::new(self)
+    }
+}
+
+impl<T> ErrorExt for T where T: Error + Send + Sync + 'static {}

exn/src/lib.rs

@@ -77,34 +77,16 @@
 
 mod debug;
 mod display;
+mod ext;
 mod impls;
 mod macros;
 mod option;
 mod result;
 
+pub use self::ext::ErrorExt;
+pub use self::ext::Ok;
 pub use self::impls::Exn;
 pub use self::impls::Frame;
 pub use self::option::OptionExt;
 pub use self::result::Result;
 pub use self::result::ResultExt;
-
-/// Equivalent to `Ok::<_, Exn<E>>(value)`.
-///
-/// This simplifies creation of an `exn::Result` in places where type inference cannot deduce the
-/// `E` type of the result &mdash; without needing to write `Ok::<_, Exn<E>>(value)`.
-///
-/// One might think that `exn::Result::Ok(value)` would work in such cases, but it does not.
-///
-/// ```console
-/// error[E0282]: type annotations needed for `std::result::Result<i32, E>`
-///   --> src/main.rs:11:13
-///    |
-/// 11 |     let _ = exn::Result::Ok(1);
-///    |         -   ^^^^^^^^^^^^^^^ cannot infer type for type parameter `E` declared on the enum `Result`
-///    |         |
-///    |         consider giving this pattern the explicit type `std::result::Result<i32, E>`, where the type parameter `E` is specified
-/// ```
-#[expect(non_snake_case)]
-pub fn Ok<T, E: std::error::Error + Send + Sync + 'static>(value: T) -> Result<T, E> {
-    Result::Ok(value)
-}

exn/src/result.rs

@@ -25,7 +25,7 @@ pub trait ResultExt {
     type Success;
 
     /// The `Err` type that would be wrapped in an [`Exn`].
-    type Error: Error + 'static;
+    type Error: Error + Send + Sync + 'static;
 
     /// Raise a new exception on the [`Exn`] inside the [`Result`].
     ///

exn/tests/simple.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use exn::ErrorExt;
 use exn::Exn;
 use exn::OptionExt;
 use exn::ResultExt;
@@ -29,7 +30,7 @@ impl std::error::Error for SimpleError {}
 
 #[test]
 fn test_error_straightforward() {
-    let e1 = Exn::new(SimpleError("E1"));
+    let e1 = SimpleError("E1").raise();
     let e2 = e1.raise(SimpleError("E2"));
     let e3 = e2.raise(SimpleError("E3"));
     let e4 = e3.raise(SimpleError("E4"));
@@ -39,21 +40,21 @@ fn test_error_straightforward() {
 
 #[test]
 fn test_error_tree() {
-    let e1 = Exn::new(SimpleError("E1"));
+    let e1 = SimpleError("E1").raise();
     let e3 = e1.raise(SimpleError("E3"));
 
-    let e9 = Exn::new(SimpleError("E9"));
+    let e9 = SimpleError("E9").raise();
     let e10 = e9.raise(SimpleError("E10"));
 
-    let e11 = Exn::new(SimpleError("E11"));
+    let e11 = SimpleError("E11").raise();
     let e12 = e11.raise(SimpleError("E12"));
 
     let e5 = Exn::from_iter([e3, e10, e12], SimpleError("E5"));
 
-    let e2 = Exn::new(SimpleError("E2"));
+    let e2 = SimpleError("E2").raise();
     let e4 = e2.raise(SimpleError("E4"));
 
-    let e7 = Exn::new(SimpleError("E7"));
+    let e7 = SimpleError("E7").raise();
     let e8 = e7.raise(SimpleError("E8"));
 
     let e6 = Exn::from_iter([e5, e4, e8], SimpleError("E6"));

exn/tests/snapshots/simple__bail.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:91:9
+An error, at exn/tests/simple.rs:92:9

exn/tests/snapshots/simple__ensure_fail.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:111:9
+An error, at exn/tests/simple.rs:112:9

exn/tests/snapshots/simple__error_straightforward.snap

@@ -2,12 +2,12 @@
 source: exn/tests/simple.rs
 expression: e5
 ---
-E5, at exn/tests/simple.rs:36:17
+E5, at exn/tests/simple.rs:37:17
 |
-|-> E4, at exn/tests/simple.rs:35:17
+|-> E4, at exn/tests/simple.rs:36:17
 |
-|-> E3, at exn/tests/simple.rs:34:17
+|-> E3, at exn/tests/simple.rs:35:17
 |
-|-> E2, at exn/tests/simple.rs:33:17
+|-> E2, at exn/tests/simple.rs:34:17
 |
-|-> E1, at exn/tests/simple.rs:32:14
+|-> E1, at exn/tests/simple.rs:33:32

exn/tests/snapshots/simple__error_tree.snap

@@ -2,26 +2,26 @@
 source: exn/tests/simple.rs
 expression: e6
 ---
-E6, at exn/tests/simple.rs:59:14
+E6, at exn/tests/simple.rs:60:14
 |
-|-> E5, at exn/tests/simple.rs:51:14
+|-> E5, at exn/tests/simple.rs:52:14
 |   |
-|   |-> E3, at exn/tests/simple.rs:43:17
+|   |-> E3, at exn/tests/simple.rs:44:17
 |   |   |
-|   |   |-> E1, at exn/tests/simple.rs:42:14
+|   |   |-> E1, at exn/tests/simple.rs:43:32
 |   |
-|   |-> E10, at exn/tests/simple.rs:46:18
+|   |-> E10, at exn/tests/simple.rs:47:18
 |   |   |
-|   |   |-> E9, at exn/tests/simple.rs:45:14
+|   |   |-> E9, at exn/tests/simple.rs:46:32
 |   |
-|   |-> E12, at exn/tests/simple.rs:49:19
+|   |-> E12, at exn/tests/simple.rs:50:19
 |       |
-|       |-> E11, at exn/tests/simple.rs:48:15
+|       |-> E11, at exn/tests/simple.rs:49:34
 |
-|-> E4, at exn/tests/simple.rs:54:17
+|-> E4, at exn/tests/simple.rs:55:17
 |   |
-|   |-> E2, at exn/tests/simple.rs:53:14
+|   |-> E2, at exn/tests/simple.rs:54:32
 |
-|-> E8, at exn/tests/simple.rs:57:17
+|-> E8, at exn/tests/simple.rs:58:17
     |
-    |-> E7, at exn/tests/simple.rs:56:14
+    |-> E7, at exn/tests/simple.rs:57:32

exn/tests/snapshots/simple__from_error.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:80:9
+An error, at exn/tests/simple.rs:81:9

exn/tests/snapshots/simple__option_ext.snap

@@ -2,4 +2,4 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-An error, at exn/tests/simple.rs:73:25
+An error, at exn/tests/simple.rs:74:25

exn/tests/snapshots/simple__result_ext.snap

@@ -2,6 +2,6 @@
 source: exn/tests/simple.rs
 expression: result.unwrap_err()
 ---
-Another error, at exn/tests/simple.rs:66:25
+Another error, at exn/tests/simple.rs:67:25
 |
-|-> An error, at exn/tests/simple.rs:66:25
+|-> An error, at exn/tests/simple.rs:67:25