better nightly detection

Cargo.toml

@@ -32,9 +32,6 @@ tls = ["native-tls", "tokio-tls"]
 # openssl
 alpn = ["openssl", "openssl/v102", "openssl/v110", "tokio-openssl"]
 
-# nightly
-nightly = []
-
 [dependencies]
 log = "0.3"
 failure = "0.1"
@@ -91,6 +88,7 @@ skeptic = "0.13"
 
 [build-dependencies]
 skeptic = "0.13"
+version_check = "0.1"
 
 [profile.release]
 lto = true

build.rs

@@ -1,4 +1,6 @@
 extern crate skeptic;
+extern crate version_check;
+
 use std::{env, fs};
 
 
@@ -11,8 +13,19 @@ fn main() {
         let f = env::var("OUT_DIR").unwrap() + "/skeptic-tests.rs";
         let _ = fs::File::create(f);
     }
+
+    match version_check::is_nightly() {
+        Some(true) => println!("cargo:rustc-cfg=actix_nightly"),
+        Some(false) => (),
+        None => (),
+    };
 }
 
 #[cfg(not(unix))]
 fn main() {
+    match version_check::is_nightly() {
+        Some(true) => println!("cargo:rustc-cfg=actix_nightly"),
+        Some(false) => (),
+        None => (),
+    };
 }

src/error.rs

@@ -4,7 +4,7 @@ use std::str::Utf8Error;
 use std::string::FromUtf8Error;
 use std::io::Error as IoError;
 
-#[cfg(feature="nightly")]
+#[cfg(actix_nightly)]
 use std::error::Error as StdError;
 
 use cookie;
@@ -76,11 +76,11 @@ impl<T: ErrorResponse> From<T> for Error {
 }
 
 /// Default error is `InternalServerError`
-#[cfg(feature="nightly")]
+#[cfg(actix_nightly)]
 default impl<T: StdError + Sync + Send + 'static> ErrorResponse for T {
-     fn error_response(&self) -> HttpResponse {
+    fn error_response(&self) -> HttpResponse {
-         HttpResponse::new(StatusCode::INTERNAL_SERVER_ERROR, Body::Empty)
+        HttpResponse::new(StatusCode::INTERNAL_SERVER_ERROR, Body::Empty)
-     }
+    }
 }
 
 /// `InternalServerError` for `JsonError`
@@ -343,6 +343,13 @@ mod tests {
     use cookie::ParseError as CookieParseError;
     use super::*;
 
+    #[test]
+    #[cfg(actix_nightly)]
+    fn test_nightly() {
+        let resp: HttpResponse = IoError::new(io::ErrorKind::Other, "test").error_response();
+        assert_eq!(resp.status(), StatusCode::INTERNAL_SERVER_ERROR);
+    }
+
     #[test]
     fn test_into_response() {
         let resp: HttpResponse = ParseError::Incomplete.error_response();

src/lib.rs

@@ -1,6 +1,6 @@
 //! Web framework for [Actix](https://github.com/actix/actix)
 
-#![cfg_attr(feature="nightly", feature(
+#![cfg_attr(actix_nightly, feature(
     specialization, // for impl ErrorResponse for std::error::Error
 ))]