chore: remove tracing. (#1680)

Historically, logging has been added haphazardly. Here, we entirely
remove logging as none of it is particularly useful. In the future, we
will add tracing back in order to expose useful data to the user of
Tokio.

tokio-executor/src/lib.rs

@@ -71,10 +71,6 @@ macro_rules! thread_local {
 #[macro_use]
 mod tests;
 
-#[cfg(any(feature = "current-thread", feature = "threadpool"))]
-#[macro_use]
-mod tracing;
-
 mod enter;
 mod error;
 mod executor;

tokio-executor/src/tracing.rs

@@ -1,84 +0,0 @@
-#![allow(unused_macros)]
-
-//! This module provides a small facade that wraps the `tracing` APIs we use, so
-//! that when the `tracing` dependency is disabled, `tracing`'s macros expand to
-//! no-ops.
-//!
-//! This means we don't have to put a `#[cfg(feature = "tracing")]` on every
-//! individual use of a `tracing` macro.
-#[cfg(not(feature = "tracing"))]
-#[derive(Clone, Debug)]
-pub(crate) struct Span {}
-
-#[cfg(feature = "tracing")]
-macro_rules! trace {
-    ($($arg:tt)+) => {
-        tracing::trace!($($arg)+)
-    };
-}
-
-#[cfg(not(feature = "tracing"))]
-macro_rules! trace {
-    ($($arg:tt)+) => {};
-}
-
-#[cfg(feature = "tracing")]
-macro_rules! debug {
-    ($($arg:tt)+) => {
-        tracing::debug!($($arg)+)
-    };
-}
-
-#[cfg(not(feature = "tracing"))]
-macro_rules! debug {
-    ($($arg:tt)+) => {};
-}
-
-#[cfg(feature = "tracing")]
-macro_rules! warn {
-    ($($arg:tt)+) => {
-        tracing::warn!($($arg)+)
-    };
-}
-
-#[cfg(not(feature = "tracing"))]
-macro_rules! warn {
-    ($($arg:tt)+) => {};
-}
-
-#[cfg(feature = "tracing")]
-macro_rules! error {
-    ($($arg:tt)+) => {
-        tracing::error!($($arg)+)
-    };
-}
-
-#[cfg(not(feature = "tracing"))]
-macro_rules! error {
-    ($($arg:tt)+) => {};
-}
-
-#[cfg(feature = "tracing")]
-macro_rules! trace_span {
-    ($($arg:tt)+) => {
-        tracing::trace_span!($($arg)+)
-    };
-}
-
-#[cfg(not(feature = "tracing"))]
-macro_rules! trace_span {
-    ($($arg:tt)+) => {
-        crate::tracing::Span::new()
-    };
-}
-
-#[cfg(not(feature = "tracing"))]
-impl Span {
-    pub(crate) fn new() -> Self {
-        Span {}
-    }
-
-    pub(crate) fn enter(&self) -> Span {
-        Span {}
-    }
-}