assert that trait solver is only created in proper infcx

Author: compiler-errors

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -36,6 +36,11 @@ pub struct FulfillmentCtxt<'tcx> {
 
 impl<'tcx> FulfillmentCtxt<'tcx> {
  pub fn new(infcx: &InferCtxt<'tcx>) -> FulfillmentCtxt<'tcx> {
+ assert!(
+ infcx.next_trait_solver(),
+ "new trait solver fulfillment context created when \
+ infcx is set up for old trait solver"
+ );
  FulfillmentCtxt { obligations: Vec::new(), usable_in_snapshot: infcx.num_open_snapshots() }
  }
 }

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -80,6 +80,11 @@ static_assert_size!(PendingPredicateObligation<'_>, 72);
 impl<'tcx> FulfillmentContext<'tcx> {
  /// Creates a new fulfillment context.
  pub(super) fn new(infcx: &InferCtxt<'tcx>) -> FulfillmentContext<'tcx> {
+ assert!(
+ !infcx.next_trait_solver(),
+ "old trait solver fulfillment context created when \
+ infcx is set up for new trait solver"
+ );
  FulfillmentContext {
  predicates: ObligationForest::new(),
  usable_in_snapshot: infcx.num_open_snapshots(),