diff --git a/Cargo.toml b/Cargo.toml
index 7b69deb..7c59940 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -36,9 +36,7 @@ libc = "0.2.100"
 log = "0.4"
 cfg-if = "1.0.0"
 
-
 [build-dependencies]
-cc = "1.0"
 rustversion = "1.0"
 
 # release build
diff --git a/benches/lib.rs b/benches/lib.rs
index 37651e9..58b45f2 100644
--- a/benches/lib.rs
+++ b/benches/lib.rs
@@ -1,3 +1,4 @@
+#![cfg(nightly)]
 #![feature(test)]
 #![allow(deprecated)]
 extern crate generator;
diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000..120f911
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,12 @@
+#[rustversion::nightly]
+const NIGHTLY: bool = true;
+
+#[rustversion::not(nightly)]
+const NIGHTLY: bool = false;
+
+fn main() {
+    println!("cargo::rustc-check-cfg=cfg(nightly)");
+    if NIGHTLY {
+        println!("cargo::rustc-cfg=nightly");
+    }
+}
diff --git a/src/detail/gen.rs b/src/detail/gen.rs
index 8c9ae64..d8a6d68 100644
--- a/src/detail/gen.rs
+++ b/src/detail/gen.rs
@@ -12,12 +12,9 @@ fn catch_unwind_filter<F: FnOnce() -> R + panic::UnwindSafe, R>(f: F) -> std::th
     INIT.call_once(|| {
         let prev_hook = panic::take_hook();
         panic::set_hook(Box::new(move |info| {
-            if let Some(e) = info.payload().downcast_ref::<Error>() {
-                match e {
-                    // this is not an error at all, ignore it
-                    Error::Cancel | Error::Done => return,
-                    _ => {}
-                }
+            // this is not an error at all, ignore it
+            if let Some(Error::Cancel | Error::Done) = info.payload().downcast_ref::<Error>() {
+                return;
             }
             prev_hook(info);
         }));
@@ -39,12 +36,9 @@ pub fn gen_init_impl(_: usize, f: *mut usize) -> ! {
     };
 
     fn check_err(cause: Box<dyn Any + Send + 'static>) {
-        if let Some(e) = cause.downcast_ref::<Error>() {
-            match e {
-                // this is not an error at all, ignore it
-                Error::Cancel | Error::Done => return,
-                _ => {}
-            }
+        // this is not an error at all, ignore it
+        if let Some(Error::Cancel | Error::Done) = cause.downcast_ref::<Error>() {
+            return;
         }
 
         error!("set panic inside generator");
diff --git a/src/lib.rs b/src/lib.rs
index 3fdcdd2..f724d5c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,8 +4,7 @@
 //!
 
 #![cfg_attr(nightly, feature(thread_local))]
-#![cfg_attr(test, deny(warnings))]
-#![deny(missing_docs)]
+#![deny(warnings, missing_docs)]
 #![allow(deprecated)]
 
 #[macro_use]
diff --git a/src/stack/windows.rs b/src/stack/windows.rs
index a0435e2..e2f1f4d 100644
--- a/src/stack/windows.rs
+++ b/src/stack/windows.rs
@@ -3,7 +3,6 @@ use std::mem;
 use std::os::raw::c_void;
 use std::ptr;
 use std::sync::atomic::{AtomicUsize, Ordering};
-use std::usize;
 
 use windows::Win32::System::Memory::*;
 use windows::Win32::System::SystemInformation::*;