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This commit is contained in:
lcnr 2023-12-19 17:39:48 +01:00
parent 4a38442c90
commit 17705ea0a8
1 changed files with 14 additions and 0 deletions
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14
compiler/rustc_trait_selection/src/solve/eval_ctxt/mod.rs
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@ -395,6 +395,20 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
original_values: Vec<ty::GenericArg<'tcx>>,
response: CanonicalResponse<'tcx>,
) -> Result<(Certainty, bool, Vec<Goal<'tcx, ty::Predicate<'tcx>>>), NoSolution> {
// The old solver did not evaluate nested goals when normalizing.
// It returned the selection constraints allowing a `Projection`
// obligation to not hold in coherence while avoiding the fatal error
// from overflow.
//
// We match this behavior here by considering all constraints
// from nested goals which are not from where-bounds. We will already
// need to track which nested goals are required by impl where-bounds
// for coinductive cycles, so we simply reuse that here.
//
// While we could consider overflow constraints in more cases, this should
// not be necessary for backcompat and results in better perf. It also
// avoids a potential inconsistency which would otherwise require some
// tracking for root goals as well. See #119071 for an example.
let keep_overflow_constraints = || {
self.search_graph.current_goal_is_normalizes_to()
&& source != GoalSource::ImplWhereBound