v0.1.x lint fix, MSRV 1.28.0 updates (#1451)

* use dyn Trait syntax where appropriate

recent rust nightly started warning that not using `dyn` was
deprecated. This requires MSRV 1.27.0+.

* rustfmt fallout from dyn additions

* stop explicit allow of rust_2018_idioms

* more dyn Trait syntax

* drop tokio-macros from 0.1.x workspace

Since tokio-macros specifies an edition=2018, we would otherwise
require MSRV 1.31.0 to build/test it. And tokio-macros isn't used with
tokio 0.1.x.

* reactor: narrow tokio-io-pool dev dep to 0.1.4

Since 0.1.5-6 is now a edition=2018 crate, which has effective MSRV
1.31.0.

* narrow tempfile dev-dep to avoid MSRV bump

tempfile 3.1.0 pulls in rand 0.7.0 and is MSRV 1.32.0

* narrow flate2 dev-dep to avoid MSRV bump

flate2 1.0.10-11 have MSRV 1.34.0.

github refs: alexcrichton/flate2-rs#207

* fs: drop deprecated tempdir crate use in tests

In particular because it pulls in old rand duplicates. Replace use
with tempfile::tempdir() which has been available since tempfile
3.0.0.

backport-of: #1312

* increase CI MSRV to 1.28.0

tokio-executor/src/enter.rs

@@ -11,7 +11,7 @@ thread_local!(static ENTERED: Cell<bool> = Cell::new(false));
 ///
 /// For more details, see [`enter` documentation](fn.enter.html)
 pub struct Enter {
-    on_exit: Vec<Box<Callback>>,
+    on_exit: Vec<Box<dyn Callback>>,
     permanent: bool,
 }
 

tokio-executor/src/executor.rs

@@ -94,7 +94,7 @@ pub trait Executor {
     /// ```
     fn spawn(
         &mut self,
-        future: Box<Future<Item = (), Error = ()> + Send>,
+        future: Box<dyn Future<Item = (), Error = ()> + Send>,
     ) -> Result<(), SpawnError>;
 
     /// Provides a best effort **hint** to whether or not `spawn` will succeed.
@@ -140,7 +140,7 @@ pub trait Executor {
 impl<E: Executor + ?Sized> Executor for Box<E> {
     fn spawn(
         &mut self,
-        future: Box<Future<Item = (), Error = ()> + Send>,
+        future: Box<dyn Future<Item = (), Error = ()> + Send>,
     ) -> Result<(), SpawnError> {
         (**self).spawn(future)
     }

tokio-executor/src/global.rs

@@ -37,7 +37,7 @@ impl DefaultExecutor {
     }
 
     #[inline]
-    fn with_current<F: FnOnce(&mut Executor) -> R, R>(f: F) -> Option<R> {
+    fn with_current<F: FnOnce(&mut dyn Executor) -> R, R>(f: F) -> Option<R> {
         EXECUTOR.with(
             |current_executor| match current_executor.replace(State::Active) {
                 State::Ready(executor_ptr) => {
@@ -57,7 +57,7 @@ enum State {
     // default executor not defined
     Empty,
     // default executor is defined and ready to be used
-    Ready(*mut Executor),
+    Ready(*mut dyn Executor),
     // default executor is currently active (used to detect recursive calls)
     Active,
 }
@@ -72,7 +72,7 @@ thread_local! {
 impl super::Executor for DefaultExecutor {
     fn spawn(
         &mut self,
-        future: Box<Future<Item = (), Error = ()> + Send>,
+        future: Box<dyn Future<Item = (), Error = ()> + Send>,
     ) -> Result<(), SpawnError> {
         DefaultExecutor::with_current(|executor| executor.spawn(future))
             .unwrap_or_else(|| Err(SpawnError::shutdown()))
@@ -210,7 +210,7 @@ where
     })
 }
 
-unsafe fn hide_lt<'a>(p: *mut (Executor + 'a)) -> *mut (Executor + 'static) {
+unsafe fn hide_lt<'a>(p: *mut (dyn Executor + 'a)) -> *mut (dyn Executor + 'static) {
     use std::mem;
     mem::transmute(p)
 }

tokio-executor/src/lib.rs

@@ -1,7 +1,5 @@
 #![deny(missing_docs, missing_debug_implementations, warnings)]
 #![doc(html_root_url = "https://docs.rs/tokio-executor/0.1.8")]
-// Our MSRV doesn't allow us to fix these warnings yet
-#![allow(rust_2018_idioms)]
 
 //! Task execution related traits and utilities.
 //!

tokio-executor/src/park.rs

@@ -128,13 +128,13 @@ pub trait Unpark: Sync + Send + 'static {
     fn unpark(&self);
 }
 
-impl Unpark for Box<Unpark> {
+impl Unpark for Box<dyn Unpark> {
     fn unpark(&self) {
         (**self).unpark()
     }
 }
 
-impl Unpark for Arc<Unpark> {
+impl Unpark for Arc<dyn Unpark> {
     fn unpark(&self) {
         (**self).unpark()
     }