Auto merge of #116849 - oli-obk:error_shenanigans, r=cjgillot

Avoid a `track_errors` by bubbling up most errors from `check_well_formed`

I believe `track_errors` is mostly papering over issues that a sufficiently convoluted query graph can hit. I made this change, while the actual change I want to do is to stop bailing out early on errors, and instead use this new `ErrorGuaranteed` to invoke `check_well_formed` for individual items before doing all the `typeck` logic on them.

This works towards resolving https://github.com/rust-lang/rust/issues/97477 and various other ICEs, as well as allowing us to use parallel rustc more (which is currently rather limited/bottlenecked due to the very sequential nature in which we do `rustc_hir_analysis::check_crate`)

cc `@SparrowLii` `@Zoxc` for the new `try_par_for_each_in` function

1 files changed, 18 insertions, 1 deletions

diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index 8bb64aa5f12..1a94b7e98fd 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -2247,7 +2247,7 @@ where
 
 /// Useful type to use with `Result<>` indicate that an error has already
 /// been reported to the user, so no need to continue checking.
-#[derive(Clone, Copy, Debug, Encodable, Decodable, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
 #[derive(HashStable_Generic)]
 pub struct ErrorGuaranteed(());
 
@@ -2259,3 +2259,20 @@ impl ErrorGuaranteed {
         ErrorGuaranteed(())
     }
 }
+
+impl<E: rustc_serialize::Encoder> Encodable<E> for ErrorGuaranteed {
+    #[inline]
+    fn encode(&self, _e: &mut E) {
+        panic!(
+            "should never serialize an `ErrorGuaranteed`, as we do not write metadata or incremental caches in case errors occurred"
+        )
+    }
+}
+impl<D: rustc_serialize::Decoder> Decodable<D> for ErrorGuaranteed {
+    #[inline]
+    fn decode(_d: &mut D) -> ErrorGuaranteed {
+        panic!(
+            "`ErrorGuaranteed` should never have been serialized to metadata or incremental caches"
+        )
+    }
+}