Auto merge of #110252 - matthiaskrgr:rollup-ovaixra, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #109810 (Replace rustdoc-ui/{c,z}-help tests with a stable run-make test )
 - #110035 (fix: ensure bad `#[test]` invocs retain correct AST)
 - #110089 (sync::mpsc: synchronize receiver disconnect with initialization)
 - #110103 (Report overflows gracefully with new solver)
 - #110122 (Fix x check --stage 1 when download-ci-llvm=false)
 - #110133 (Do not use ImplDerivedObligationCause for inherent impl method error reporting)
 - #110135 (Revert "Don't recover lifetimes/labels containing emojis as character literals")
 - #110235 (Fix `--extend-css` option)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

1 files changed, 24 insertions, 5 deletions

diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index 76a2a587911..32bd10f0beb 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -1,6 +1,7 @@
 use std::mem;
 
 use rustc_infer::infer::InferCtxt;
+use rustc_infer::traits::solve::MaybeCause;
 use rustc_infer::traits::Obligation;
 use rustc_infer::traits::{
     query::NoSolution, FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes,
@@ -41,13 +42,31 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
         self.obligations.push(obligation);
     }
 
-    fn collect_remaining_errors(&mut self) -> Vec<FulfillmentError<'tcx>> {
+    fn collect_remaining_errors(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
         self.obligations
             .drain(..)
-            .map(|obligation| FulfillmentError {
-                obligation: obligation.clone(),
-                code: FulfillmentErrorCode::CodeAmbiguity,
-                root_obligation: obligation,
+            .map(|obligation| {
+                let code =
+                    infcx.probe(|_| match infcx.evaluate_root_goal(obligation.clone().into()) {
+                        Ok((_, Certainty::Maybe(MaybeCause::Ambiguity), _)) => {
+                            FulfillmentErrorCode::CodeAmbiguity { overflow: false }
+                        }
+                        Ok((_, Certainty::Maybe(MaybeCause::Overflow), _)) => {
+                            FulfillmentErrorCode::CodeAmbiguity { overflow: true }
+                        }
+                        Ok((_, Certainty::Yes, _)) => {
+                            bug!("did not expect successful goal when collecting ambiguity errors")
+                        }
+                        Err(_) => {
+                            bug!("did not expect selection error when collecting ambiguity errors")
+                        }
+                    });
+
+                FulfillmentError {
+                    obligation: obligation.clone(),
+                    code,
+                    root_obligation: obligation,
+                }
             })
             .collect()
     }