enable some warnings that rustc bootstrap enables

src/tools/miri/miri

@@ -243,7 +243,7 @@ if [ -z "$CARGO_PROFILE_DEV_OPT_LEVEL" ]; then
     export CARGO_PROFILE_DEV_OPT_LEVEL=2
 fi
 # Enable rustc-specific lints (ignored without `-Zunstable-options`).
-export RUSTFLAGS="-Zunstable-options -Wrustc::internal $RUSTFLAGS"
+export RUSTFLAGS="-Zunstable-options -Wrustc::internal -Wrust_2018_idioms -Wunused_lifetimes -Wsemicolon_in_expressions_from_macros $RUSTFLAGS"
 # We set the rpath so that Miri finds the private rustc libraries it needs.
 export RUSTFLAGS="-C link-args=-Wl,-rpath,$LIBDIR $RUSTFLAGS"
 

src/tools/miri/src/shims/unix/linux/fd/epoll.rs

@@ -36,7 +36,7 @@ fn as_epoll_handle<'tcx>(&mut self) -> InterpResult<'tcx, &mut Epoll> {
         Ok(self)
     }
 
-    fn dup<'tcx>(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
+    fn dup(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
         Ok(Box::new(self.clone()))
     }
 

src/tools/miri/src/shims/unix/linux/fd/event.rs

@@ -21,7 +21,7 @@ fn name(&self) -> &'static str {
         "event"
     }
 
-    fn dup<'tcx>(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
+    fn dup(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
         Ok(Box::new(Event { val: self.val }))
     }
 

src/tools/miri/src/shims/unix/linux/fd/socketpair.rs

@@ -15,7 +15,7 @@ fn name(&self) -> &'static str {
         "socketpair"
     }
 
-    fn dup<'tcx>(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
+    fn dup(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
         Ok(Box::new(SocketPair))
     }