rust-timer simulated merge of 43ba840

Original message:
Rollup merge of rust-lang#74071 - petrochenkov:cload3, r=matthewjasper

rustc_metadata: Make crate loading fully speculative

Instead of reporting `span_err`s on the spot crate loading errors are now wrapped into the `CrateError` enum and returned, so they are reported only at the top level `resolve_crate` call, and not reported at all if we are resolving speculatively with `maybe_resolve_crate`.

As a result we can attempt loading crates for error recovery (e.g. import suggestions) without any risk of producing extra errors.
Also, this means better separation between error reporting and actual logic.

Fixes rust-lang#55103
Fixes rust-lang#56590

Author: rust-timer

src/libcore/task/mod.rs

@@ -9,3 +9,7 @@ pub use self::poll::Poll;
 mod wake;
 #[stable(feature = "futures_api", since = "1.36.0")]
 pub use self::wake::{Context, RawWaker, RawWakerVTable, Waker};
+
+mod ready;
+#[unstable(feature = "ready_macro", issue = "70922")]
+pub use ready::ready;

src/libcore/task/ready.rs

@@ -0,0 +1,60 @@
+/// Extracts the successful type of a `Poll<T>`.
+///
+/// This macro bakes in propagation of `Pending` signals by returning early.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(future_readiness_fns)]
+/// #![feature(ready_macro)]
+///
+/// use core::task::{ready, Context, Poll};
+/// use core::future::{self, Future};
+/// use core::pin::Pin;
+///
+/// pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
+///     let mut fut = future::ready(42);
+///     let fut = Pin::new(&mut fut);
+///
+///     let num = ready!(fut.poll(cx));
+///     # drop(num);
+///     // ... use num
+///
+///     Poll::Ready(())
+/// }
+/// ```
+///
+/// The `ready!` call expands to:
+///
+/// ```
+/// # #![feature(future_readiness_fns)]
+/// # #![feature(ready_macro)]
+/// #
+/// # use core::task::{Context, Poll};
+/// # use core::future::{self, Future};
+/// # use core::pin::Pin;
+/// #
+/// # pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
+///     # let mut fut = future::ready(42);
+///     # let fut = Pin::new(&mut fut);
+///     #
+/// let num = match fut.poll(cx) {
+///     Poll::Ready(t) => t,
+///     Poll::Pending => return Poll::Pending,
+/// };
+///     # drop(num);
+///     # // ... use num
+///     #
+///     # Poll::Ready(())
+/// # }
+/// ```
+#[unstable(feature = "ready_macro", issue = "70922")]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro ready($e:expr) {
+    match $e {
+        $crate::task::Poll::Ready(t) => t,
+        $crate::task::Poll::Pending => {
+            return $crate::task::Poll::Pending;
+        }
+    }
+}

src/librustc_error_codes/error_codes.rs

@@ -554,7 +554,7 @@ E0770: include_str!("./error_codes/E0770.md"),
 //  E0420, merged into 532
 //  E0421, merged into 531
 //  E0427, merged into 530
-    E0456, // plugin `..` is not available for triple `..`
+//  E0456, // plugin `..` is not available for triple `..`
     E0457, // plugin `..` only found in rlib format, but must be available...
     E0460, // found possibly newer version of crate `..`
     E0461, // couldn't find crate `..` with expected target triple ..