Adjust diagnostic items for mpmc/mpsc Receiver and Sender

`MpscReceiver` aligns with `MpscSender`.  The original name appears to
not actually have been in use, for better or worse.

Along the way, sprinkle the attribute onto `mpmc::Receiver` and
`mpmc::Sender` too.

Author: cammeresi

library/std/src/sync/mpmc/mod.rs

@@ -297,6 +297,7 @@ pub fn sync_channel<T>(cap: usize) -> (Sender<T>, Receiver<T>) {
 /// assert_eq!(3, msg + msg2);
 /// ```
 #[unstable(feature = "mpmc_channel", issue = "126840")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "MpmcSender")]
 pub struct Sender<T> {
     flavor: SenderFlavor<T>,
 }
@@ -722,6 +723,7 @@ impl<T> fmt::Debug for Sender<T> {
 /// rx_thread_2.join().unwrap();
 /// ```
 #[unstable(feature = "mpmc_channel", issue = "126840")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "MpmcReceiver")]
 pub struct Receiver<T> {
     flavor: ReceiverFlavor<T>,
 }

library/std/src/sync/mpsc.rs

@@ -173,7 +173,7 @@ use crate::{error, fmt};
 /// println!("{}", recv.recv().unwrap()); // Received after 2 seconds
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
-#[cfg_attr(not(test), rustc_diagnostic_item = "Receiver")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "MpscReceiver")]
 pub struct Receiver<T> {
     inner: mpmc::Receiver<T>,
 }

src/tools/clippy/clippy_utils/src/sym.rs

@@ -90,6 +90,10 @@ generate! {
     MAX,
     MIN,
     MaybeDef,
+    MpmcReceiver,
+    MpmcSender,
+    MpscReceiver,
+    MpscSender,
     MsrvStack,
     Octal,
     OpenOptions,
@@ -99,7 +103,6 @@ generate! {
     PathBuf,
     PathLookup,
     RangeBounds,
-    Receiver,
     RefCellRef,
     RefCellRefMut,
     Regex,

src/tools/clippy/clippy_utils/src/ty/mod.rs

@@ -192,7 +192,8 @@ pub fn has_iter_method(cx: &LateContext<'_>, probably_ref_ty: Ty<'_>) -> Option<
         sym::HashMap,
         sym::PathBuf,
         sym::Path,
-        sym::Receiver,
+        sym::MpscReceiver,
+        sym::MpmcReceiver,
     ];
 
     let ty_to_check = match probably_ref_ty.kind() {