ci: enable clippy lints (#1335)

tokio-executor/src/global.rs

@@ -180,6 +180,8 @@ where
 
 unsafe fn hide_lt<'a>(p: *mut (dyn Executor + 'a)) -> *mut (dyn Executor + 'static) {
     use std::mem;
+    // false positive: https://github.com/rust-lang/rust-clippy/issues/2906
+    #[allow(clippy::transmute_ptr_to_ptr)]
     mem::transmute(p)
 }
 

tokio-executor/src/park.rs

@@ -218,6 +218,12 @@ impl Park for ParkThread {
     }
 }
 
+impl Default for ParkThread {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 // ===== impl UnparkThread =====
 
 impl Unpark for UnparkThread {