1 files changed, 81 insertions, 0 deletions
diff --git a/third_party/rust/error-chain/src/quick_main.rs b/third_party/rust/error-chain/src/quick_main.rs
new file mode 100644
index 0000000000..a6f093d2b3
--- /dev/null
+++ b/third_party/rust/error-chain/src/quick_main.rs
@@ -0,0 +1,81 @@
+/// Convenient wrapper to be able to use `?` and such in the main. You can
+/// use it with a separated function:
+///
+/// ```
+/// # #[macro_use] extern crate error_chain;
+/// # error_chain! {}
+/// # fn main() {
+/// quick_main!(run);
+/// # }
+///
+/// fn run() -> Result<()> {
+///     Err("error".into())
+/// }
+/// ```
+///
+/// or with a closure:
+///
+/// ```
+/// # #[macro_use] extern crate error_chain;
+/// # error_chain! {}
+/// # fn main() {
+/// quick_main!(|| -> Result<()> {
+///     Err("error".into())
+/// });
+/// # }
+/// ```
+///
+/// You can also set the exit value of the process by returning a type that implements [`ExitCode`](trait.ExitCode.html):
+///
+/// ```
+/// # #[macro_use] extern crate error_chain;
+/// # error_chain! {}
+/// # fn main() {
+/// quick_main!(run);
+/// # }
+///
+/// fn run() -> Result<i32> {
+///     Err("error".into())
+/// }
+/// ```
+#[macro_export]
+macro_rules! quick_main {
+    ($main:expr) => {
+        fn main() {
+            use std::io::Write;
+
+            ::std::process::exit(match $main() {
+                Ok(ret) => $crate::ExitCode::code(ret),
+                Err(ref e) => {
+                    write!(
+                        &mut ::std::io::stderr(),
+                        "{}",
+                        $crate::ChainedError::display_chain(e)
+                    )
+                    .expect("Error writing to stderr");
+
+                    1
+                }
+            });
+        }
+    };
+}
+
+/// Represents a value that can be used as the exit status of the process.
+/// See [`quick_main!`](macro.quick_main.html).
+pub trait ExitCode {
+    /// Returns the value to use as the exit status.
+    fn code(self) -> i32;
+}
+
+impl ExitCode for i32 {
+    fn code(self) -> i32 {
+        self
+    }
+}
+
+impl ExitCode for () {
+    fn code(self) -> i32 {
+        0
+    }
+}