Opt-in diagnostics reporting to avoid doing extra work in the new solver

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -15,7 +15,7 @@ use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_span::symbol::sym;
 
-use crate::traits::FulfillmentError;
+use crate::traits::{FulfillmentError, ScrubbedTraitError};
 
 use super::eval_ctxt::GenerateProofTree;
 use super::inspect::{self, ProofTreeInferCtxtExt, ProofTreeVisitor};
@@ -226,6 +226,17 @@ impl<'tcx> FromSolverError<'tcx, NextSolverError<'tcx>> for FulfillmentError<'tc
     }
 }
 
+impl<'tcx> FromSolverError<'tcx, NextSolverError<'tcx>> for ScrubbedTraitError {
+    fn from_solver_error(_infcx: &InferCtxt<'tcx>, error: NextSolverError<'tcx>) -> Self {
+        match error {
+            NextSolverError::TrueError(_) => ScrubbedTraitError::TrueError,
+            NextSolverError::Ambiguity(_) | NextSolverError::Overflow(_) => {
+                ScrubbedTraitError::Ambiguity
+            }
+        }
+    }
+}
+
 fn fulfillment_error_for_no_solution<'tcx>(
     infcx: &InferCtxt<'tcx>,
     root_obligation: PredicateObligation<'tcx>,

compiler/rustc_trait_selection/src/solve/inspect/analyse.rs

@@ -12,6 +12,7 @@
 use rustc_ast_ir::try_visit;
 use rustc_ast_ir::visit::VisitorResult;
 use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, InferOk};
+use rustc_infer::traits::FulfillmentErrorLike as _;
 use rustc_macros::extension;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::solve::{inspect, QueryResult};