Remove glob imports for ObligationCauseCode

24 files changed, 279 insertions, 178 deletions

diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 81178344407..55bf06c1ec8 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -2012,9 +2012,9 @@ pub(super) fn check_type_bounds<'tcx>(
     );
     let mk_cause = |span: Span| {
         let code = if span.is_dummy() {
-            traits::ItemObligation(trait_ty.def_id)
+            ObligationCauseCode::ItemObligation(trait_ty.def_id)
         } else {
-            traits::BindingObligation(trait_ty.def_id, span)
+            ObligationCauseCode::BindingObligation(trait_ty.def_id, span)
         };
         ObligationCause::new(impl_ty_span, impl_ty_def_id, code)
     };
@@ -2251,7 +2251,8 @@ fn try_report_async_mismatch<'tcx>(
     };
 
     for error in errors {
-        if let traits::BindingObligation(def_id, _) = *error.root_obligation.cause.code()
+        if let ObligationCauseCode::BindingObligation(def_id, _) =
+            *error.root_obligation.cause.code()
             && def_id == async_future_def_id
             && let Some(proj) = error.root_obligation.predicate.to_opt_poly_projection_pred()
             && let Some(proj) = proj.no_bound_vars()
diff --git a/compiler/rustc_hir_analysis/src/check/dropck.rs b/compiler/rustc_hir_analysis/src/check/dropck.rs
index 82a6b6b6f2c..be412dde968 100644
--- a/compiler/rustc_hir_analysis/src/check/dropck.rs
+++ b/compiler/rustc_hir_analysis/src/check/dropck.rs
@@ -5,6 +5,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{codes::*, struct_span_code_err, ErrorGuaranteed};
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::ty::util::CheckRegions;
 use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, TyCtxt};
@@ -139,7 +140,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
     for (pred, span) in tcx.predicates_of(drop_impl_def_id).instantiate_identity(tcx) {
         let normalize_cause = traits::ObligationCause::misc(span, adt_def_id);
         let pred = ocx.normalize(&normalize_cause, param_env, pred);
-        let cause = traits::ObligationCause::new(span, adt_def_id, traits::DropImpl);
+        let cause = traits::ObligationCause::new(span, adt_def_id, ObligationCauseCode::DropImpl);
         ocx.register_obligation(traits::Obligation::new(tcx, cause, param_env, pred));
     }
 
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index ddfb88d72d8..124de69140e 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -1136,7 +1136,7 @@ fn check_type_defn<'tcx>(
                     traits::ObligationCause::new(
                         hir_ty.span,
                         wfcx.body_def_id,
-                        traits::FieldSized {
+                        ObligationCauseCode::FieldSized {
                             adt_kind: match &item.kind {
                                 ItemKind::Struct(..) => AdtKind::Struct,
                                 ItemKind::Union(..) => AdtKind::Union,
@@ -1161,7 +1161,7 @@ fn check_type_defn<'tcx>(
                 let cause = traits::ObligationCause::new(
                     tcx.def_span(discr_def_id),
                     wfcx.body_def_id,
-                    traits::MiscObligation,
+                    ObligationCauseCode::MiscObligation,
                 );
                 wfcx.register_obligation(traits::Obligation::new(
                     tcx,
@@ -1278,7 +1278,11 @@ fn check_item_type(
         wfcx.register_wf_obligation(ty_span, Some(WellFormedLoc::Ty(item_id)), item_ty.into());
         if forbid_unsized {
             wfcx.register_bound(
-                traits::ObligationCause::new(ty_span, wfcx.body_def_id, traits::WellFormed(None)),
+                traits::ObligationCause::new(
+                    ty_span,
+                    wfcx.body_def_id,
+                    ObligationCauseCode::WellFormed(None),
+                ),
                 wfcx.param_env,
                 item_ty,
                 tcx.require_lang_item(LangItem::Sized, None),
@@ -1293,7 +1297,11 @@ fn check_item_type(
 
         if should_check_for_sync {
             wfcx.register_bound(
-                traits::ObligationCause::new(ty_span, wfcx.body_def_id, traits::SharedStatic),
+                traits::ObligationCause::new(
+                    ty_span,
+                    wfcx.body_def_id,
+                    ObligationCauseCode::SharedStatic,
+                ),
                 wfcx.param_env,
                 item_ty,
                 tcx.require_lang_item(LangItem::Sync, Some(ty_span)),
@@ -1542,7 +1550,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
             let cause = traits::ObligationCause::new(
                 sp,
                 wfcx.body_def_id,
-                traits::ItemObligation(def_id.to_def_id()),
+                ObligationCauseCode::ItemObligation(def_id.to_def_id()),
             );
             traits::Obligation::new(tcx, cause, wfcx.param_env, pred)
         });
@@ -1982,7 +1990,11 @@ impl<'tcx> WfCheckingCtxt<'_, 'tcx> {
 
                 let obligation = traits::Obligation::new(
                     tcx,
-                    traits::ObligationCause::new(span, self.body_def_id, traits::TrivialBound),
+                    traits::ObligationCause::new(
+                        span,
+                        self.body_def_id,
+                        ObligationCauseCode::TrivialBound,
+                    ),
                     empty_env,
                     pred,
                 );
diff --git a/compiler/rustc_hir_typeck/src/callee.rs b/compiler/rustc_hir_typeck/src/callee.rs
index 1a015eb0d96..defb557867b 100644
--- a/compiler/rustc_hir_typeck/src/callee.rs
+++ b/compiler/rustc_hir_typeck/src/callee.rs
@@ -9,6 +9,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{self, CtorKind, Namespace, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir_analysis::autoderef::Autoderef;
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_infer::{
     infer,
     traits::{self, Obligation, ObligationCause},
@@ -117,7 +118,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         // we must check that return type of called functions is WF:
-        self.register_wf_obligation(output.into(), call_expr.span, traits::WellFormed(None));
+        self.register_wf_obligation(
+            output.into(),
+            call_expr.span,
+            ObligationCauseCode::WellFormed(None),
+        );
 
         output
     }
@@ -524,9 +529,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.register_bound(
                     ty,
                     self.tcx.require_lang_item(hir::LangItem::Tuple, Some(sp)),
-                    traits::ObligationCause::new(sp, self.body_id, traits::RustCall),
+                    traits::ObligationCause::new(sp, self.body_id, ObligationCauseCode::RustCall),
                 );
-                self.require_type_is_sized(ty, sp, traits::RustCall);
+                self.require_type_is_sized(ty, sp, ObligationCauseCode::RustCall);
             } else {
                 self.dcx().emit_err(errors::RustCallIncorrectArgs { span: sp });
             }
diff --git a/compiler/rustc_hir_typeck/src/check.rs b/compiler/rustc_hir_typeck/src/check.rs
index 386edc37765..89e64cf5f0d 100644
--- a/compiler/rustc_hir_typeck/src/check.rs
+++ b/compiler/rustc_hir_typeck/src/check.rs
@@ -14,7 +14,6 @@ use rustc_middle::ty::{self, Binder, Ty, TyCtxt};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::symbol::sym;
 use rustc_target::spec::abi::Abi;
-use rustc_trait_selection::traits;
 use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
 
 /// Helper used for fns and closures. Does the grungy work of checking a function
@@ -76,7 +75,7 @@ pub(super) fn check_fn<'a, 'tcx>(
             fcx.register_wf_obligation(
                 param_ty.into(),
                 param.span,
-                traits::WellFormed(Some(WellFormedLoc::Param {
+                ObligationCauseCode::WellFormed(Some(WellFormedLoc::Param {
                     function: fn_def_id,
                     param_idx: idx,
                 })),
@@ -101,7 +100,7 @@ pub(super) fn check_fn<'a, 'tcx>(
                 param.pat.span,
                 // ty.span == binding_span iff this is a closure parameter with no type ascription,
                 // or if it's an implicit `self` parameter
-                traits::SizedArgumentType(
+                ObligationCauseCode::SizedArgumentType(
                     if ty_span == Some(param.span) && tcx.is_closure_like(fn_def_id.into()) {
                         None
                     } else {
@@ -121,10 +120,18 @@ pub(super) fn check_fn<'a, 'tcx>(
         hir::FnRetTy::Return(ty) => ty.span,
     };
 
-    fcx.require_type_is_sized(declared_ret_ty, return_or_body_span, traits::SizedReturnType);
+    fcx.require_type_is_sized(
+        declared_ret_ty,
+        return_or_body_span,
+        ObligationCauseCode::SizedReturnType,
+    );
     // We checked the root's signature during wfcheck, but not the child.
     if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
-        fcx.require_type_is_sized(declared_ret_ty, return_or_body_span, traits::WellFormed(None));
+        fcx.require_type_is_sized(
+            declared_ret_ty,
+            return_or_body_span,
+            ObligationCauseCode::WellFormed(None),
+        );
     }
 
     fcx.is_whole_body.set(true);
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index 6c73c77bf52..f52f95db6d3 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -8,6 +8,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
 use rustc_infer::infer::{BoundRegionConversionTime, DefineOpaqueTypes};
 use rustc_infer::infer::{InferOk, InferResult};
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_macros::{TypeFoldable, TypeVisitable};
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::GenericArgs;
@@ -119,7 +120,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
                     | hir::CoroutineKind::Coroutine(_) => {
                         let yield_ty = self.next_ty_var(expr_span);
-                        self.require_type_is_sized(yield_ty, expr_span, traits::SizedYieldType);
+                        self.require_type_is_sized(
+                            yield_ty,
+                            expr_span,
+                            ObligationCauseCode::SizedYieldType,
+                        );
                         yield_ty
                     }
                     // HACK(-Ztrait-solver=next): In the *old* trait solver, we must eagerly
@@ -128,7 +133,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // not a problem.
                     hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _) => {
                         let yield_ty = self.next_ty_var(expr_span);
-                        self.require_type_is_sized(yield_ty, expr_span, traits::SizedYieldType);
+                        self.require_type_is_sized(
+                            yield_ty,
+                            expr_span,
+                            ObligationCauseCode::SizedYieldType,
+                        );
 
                         Ty::new_adt(
                             tcx,
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index a7e147b4b18..00371f21277 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -573,7 +573,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     self.require_type_is_sized_deferred(
                         input,
                         span,
-                        traits::SizedArgumentType(None),
+                        ObligationCauseCode::SizedArgumentType(None),
                     );
                 }
             }
@@ -591,7 +591,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.require_type_is_sized_deferred(
                 output,
                 call.map_or(expr.span, |e| e.span),
-                traits::SizedCallReturnType,
+                ObligationCauseCode::SizedCallReturnType,
             );
         }
 
@@ -1249,7 +1249,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         });
 
-        self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
+        self.require_type_is_sized(lhs_ty, lhs.span, ObligationCauseCode::AssignmentLhsSized);
 
         if let Err(guar) = (lhs_ty, rhs_ty).error_reported() {
             Ty::new_error(self.tcx, guar)
@@ -1471,7 +1471,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         crate::GatherLocalsVisitor::new(&fcx).visit_body(body);
 
         let ty = fcx.check_expr_with_expectation(body.value, expected);
-        fcx.require_type_is_sized(ty, body.value.span, traits::ConstSized);
+        fcx.require_type_is_sized(ty, body.value.span, ObligationCauseCode::ConstSized);
         fcx.write_ty(block.hir_id, ty);
         ty
     }
@@ -1517,7 +1517,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let ty = Ty::new_array_with_const_len(tcx, t, count);
 
-        self.register_wf_obligation(ty.into(), expr.span, traits::WellFormed(None));
+        self.register_wf_obligation(ty.into(), expr.span, ObligationCauseCode::WellFormed(None));
 
         ty
     }
@@ -1607,7 +1607,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let Err(guar) = tuple.error_reported() {
             Ty::new_error(self.tcx, guar)
         } else {
-            self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
+            self.require_type_is_sized(
+                tuple,
+                expr.span,
+                ObligationCauseCode::TupleInitializerSized,
+            );
             tuple
         }
     }
@@ -1646,7 +1650,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             base_expr,
         );
 
-        self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
+        self.require_type_is_sized(adt_ty, expr.span, ObligationCauseCode::StructInitializerSized);
         adt_ty
     }
 
@@ -3079,7 +3083,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             polarity: ty::PredicatePolarity::Positive,
                         }),
                         |derived| {
-                            traits::ImplDerivedObligation(Box::new(
+                            ObligationCauseCode::ImplDerivedObligation(Box::new(
                                 traits::ImplDerivedObligationCause {
                                     derived,
                                     impl_or_alias_def_id: impl_def_id,
@@ -3177,7 +3181,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     fn check_expr_asm_operand(&self, expr: &'tcx hir::Expr<'tcx>, is_input: bool) {
         let needs = if is_input { Needs::None } else { Needs::MutPlace };
         let ty = self.check_expr_with_needs(expr, needs);
-        self.require_type_is_sized(ty, expr.span, traits::InlineAsmSized);
+        self.require_type_is_sized(ty, expr.span, ObligationCauseCode::InlineAsmSized);
 
         if !is_input && !expr.is_syntactic_place_expr() {
             self.dcx()
@@ -3348,7 +3352,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let field_ty = self.field_ty(expr.span, field, args);
 
                     // FIXME: DSTs with static alignment should be allowed
-                    self.require_type_is_sized(field_ty, expr.span, traits::MiscObligation);
+                    self.require_type_is_sized(
+                        field_ty,
+                        expr.span,
+                        ObligationCauseCode::MiscObligation,
+                    );
 
                     if field.vis.is_accessible_from(sub_def_scope, self.tcx) {
                         self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
@@ -3376,7 +3384,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let field_ty = self.field_ty(expr.span, field, args);
 
                         // FIXME: DSTs with static alignment should be allowed
-                        self.require_type_is_sized(field_ty, expr.span, traits::MiscObligation);
+                        self.require_type_is_sized(
+                            field_ty,
+                            expr.span,
+                            ObligationCauseCode::MiscObligation,
+                        );
 
                         if field.vis.is_accessible_from(def_scope, self.tcx) {
                             self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span, None);
@@ -3397,7 +3409,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         && field.name == sym::integer(index)
                     {
                         for ty in tys.iter().take(index + 1) {
-                            self.require_type_is_sized(ty, expr.span, traits::MiscObligation);
+                            self.require_type_is_sized(
+                                ty,
+                                expr.span,
+                                ObligationCauseCode::MiscObligation,
+                            );
                         }
                         if let Some(&field_ty) = tys.get(index) {
                             field_indices.push((FIRST_VARIANT, index.into()));
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 552747bdc52..887c0c9f4f0 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -409,7 +409,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     pub fn lower_ty(&self, hir_ty: &hir::Ty<'tcx>) -> LoweredTy<'tcx> {
         let ty = self.lowerer().lower_ty(hir_ty);
-        self.register_wf_obligation(ty.into(), hir_ty.span, traits::WellFormed(None));
+        self.register_wf_obligation(ty.into(), hir_ty.span, ObligationCauseCode::WellFormed(None));
         LoweredTy::from_raw(self, hir_ty.span, ty)
     }
 
@@ -520,7 +520,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         for arg in args.iter().filter(|arg| {
             matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
         }) {
-            self.register_wf_obligation(arg, expr.span, traits::WellFormed(None));
+            self.register_wf_obligation(arg, expr.span, ObligationCauseCode::WellFormed(None));
         }
     }
 
@@ -775,7 +775,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
         if let Some(&cached_result) = self.typeck_results.borrow().type_dependent_defs().get(hir_id)
         {
-            self.register_wf_obligation(ty.raw.into(), qself.span, traits::WellFormed(None));
+            self.register_wf_obligation(
+                ty.raw.into(),
+                qself.span,
+                ObligationCauseCode::WellFormed(None),
+            );
             // Return directly on cache hit. This is useful to avoid doubly reporting
             // errors with default match binding modes. See #44614.
             let def = cached_result.map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id));
@@ -814,7 +818,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     self.register_wf_obligation(
                         ty.raw.into(),
                         qself.span,
-                        traits::WellFormed(None),
+                        ObligationCauseCode::WellFormed(None),
                     );
                 }
 
@@ -848,7 +852,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             });
 
         if result.is_ok() {
-            self.register_wf_obligation(ty.raw.into(), qself.span, traits::WellFormed(None));
+            self.register_wf_obligation(
+                ty.raw.into(),
+                qself.span,
+                ObligationCauseCode::WellFormed(None),
+            );
         }
 
         // Write back the new resolution.
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
index c41ad40aa79..56745c1245b 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
@@ -14,8 +14,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         error: &mut traits::FulfillmentError<'tcx>,
     ) -> bool {
-        let (traits::ExprItemObligation(def_id, hir_id, idx)
-        | traits::ExprBindingObligation(def_id, _, hir_id, idx)) =
+        let (ObligationCauseCode::ExprItemObligation(def_id, hir_id, idx)
+        | ObligationCauseCode::ExprBindingObligation(def_id, _, hir_id, idx)) =
             *error.obligation.cause.code().peel_derives()
         else {
             return false;
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 7266be17649..73bc5fd7d50 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -203,7 +203,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // All the input types from the fn signature must outlive the call
         // so as to validate implied bounds.
         for (&fn_input_ty, arg_expr) in iter::zip(formal_input_tys, provided_args) {
-            self.register_wf_obligation(fn_input_ty.into(), arg_expr.span, traits::MiscObligation);
+            self.register_wf_obligation(
+                fn_input_ty.into(),
+                arg_expr.span,
+                ObligationCauseCode::MiscObligation,
+            );
         }
 
         let mut err_code = E0061;
diff --git a/compiler/rustc_hir_typeck/src/gather_locals.rs b/compiler/rustc_hir_typeck/src/gather_locals.rs
index af5cbad32c8..13e4b625e2d 100644
--- a/compiler/rustc_hir_typeck/src/gather_locals.rs
+++ b/compiler/rustc_hir_typeck/src/gather_locals.rs
@@ -2,11 +2,11 @@ use crate::FnCtxt;
 use rustc_hir as hir;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{HirId, PatKind};
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::UserType;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::Span;
-use rustc_trait_selection::traits;
 
 /// Provides context for checking patterns in declarations. More specifically this
 /// allows us to infer array types if the pattern is irrefutable and allows us to infer
@@ -146,7 +146,7 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
                         p.span,
                         // ty_span == ident.span iff this is a closure parameter with no type
                         // ascription, or if it's an implicit `self` parameter
-                        traits::SizedArgumentType(
+                        ObligationCauseCode::SizedArgumentType(
                             if ty_span == ident.span
                                 && self.fcx.tcx.is_closure_like(self.fcx.body_id.into())
                             {
@@ -159,7 +159,11 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
                 }
             } else {
                 if !self.fcx.tcx.features().unsized_locals {
-                    self.fcx.require_type_is_sized(var_ty, p.span, traits::VariableType(p.hir_id));
+                    self.fcx.require_type_is_sized(
+                        var_ty,
+                        p.span,
+                        ObligationCauseCode::VariableType(p.hir_id),
+                    );
                 }
             }
 
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 53ccc841ca9..e270e589505 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -62,7 +62,6 @@ use rustc_hir_analysis::check::check_abi;
 use rustc_hir_analysis::hir_ty_lowering::HirTyLowerer;
 use rustc_infer::traits::{ObligationCauseCode, ObligationInspector, WellFormedLoc};
 use rustc_middle::query::Providers;
-use rustc_middle::traits;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_session::config;
 use rustc_span::def_id::LocalDefId;
@@ -170,7 +169,7 @@ fn typeck_with_fallback<'tcx>(
         let wf_code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(def_id)));
         fcx.register_wf_obligation(expected_type.into(), body.value.span, wf_code);
 
-        fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
+        fcx.require_type_is_sized(expected_type, body.value.span, ObligationCauseCode::ConstSized);
 
         // Gather locals in statics (because of block expressions).
         GatherLocalsVisitor::new(&fcx).visit_body(body);
diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index 128e599618a..f844083b57c 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -589,7 +589,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // the function type must also be well-formed (this is not
         // implied by the args being well-formed because of inherent
         // impls and late-bound regions - see issue #28609).
-        self.register_wf_obligation(fty.into(), self.span, traits::WellFormed(None));
+        self.register_wf_obligation(fty.into(), self.span, ObligationCauseCode::WellFormed(None));
     }
 
     ///////////////////////////////////////////////////////////////////////////
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 5708630ca3c..163fcbf8cbb 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -15,6 +15,7 @@ use rustc_infer::infer::canonical::{Canonical, QueryResponse};
 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
 use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_infer::infer::{self, InferOk, TyCtxtInferExt};
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::middle::stability;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::fast_reject::{simplify_type, TreatParams};
@@ -1401,9 +1402,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     ocx.register_obligations(traits::predicates_for_generics(
                         |idx, span| {
                             let code = if span.is_dummy() {
-                                traits::ExprItemObligation(impl_def_id, self.scope_expr_id, idx)
+                                ObligationCauseCode::ExprItemObligation(
+                                    impl_def_id,
+                                    self.scope_expr_id,
+                                    idx,
+                                )
                             } else {
-                                traits::ExprBindingObligation(
+                                ObligationCauseCode::ExprBindingObligation(
                                     impl_def_id,
                                     span,
                                     self.scope_expr_id,
diff --git a/compiler/rustc_hir_typeck/src/op.rs b/compiler/rustc_hir_typeck/src/op.rs
index 3df553bb037..dca1cda0694 100644
--- a/compiler/rustc_hir_typeck/src/op.rs
+++ b/compiler/rustc_hir_typeck/src/op.rs
@@ -19,7 +19,7 @@ use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::error_reporting::suggestions::TypeErrCtxtExt as _;
-use rustc_trait_selection::traits::{self, FulfillmentError, ObligationCtxt};
+use rustc_trait_selection::traits::{FulfillmentError, ObligationCtxt};
 use rustc_type_ir::TyKind::*;
 
 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
@@ -884,7 +884,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let input_types = opt_rhs_ty.as_slice();
         let cause = self.cause(
             span,
-            traits::BinOp {
+            ObligationCauseCode::BinOp {
                 lhs_hir_id: lhs_expr.hir_id,
                 rhs_hir_id: opt_rhs_expr.map(|expr| expr.hir_id),
                 rhs_span: opt_rhs_expr.map(|expr| expr.span),
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index fe2deee378e..0e677d0560f 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -18,7 +18,7 @@ use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, Span, DUMMY_SP};
 use rustc_target::abi::FieldIdx;
-use rustc_trait_selection::traits::{ObligationCause, Pattern};
+use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
 use ty::VariantDef;
 
 use std::cmp;
@@ -88,8 +88,11 @@ struct PatInfo<'tcx, 'a> {
 
 impl<'tcx> FnCtxt<'_, 'tcx> {
     fn pattern_cause(&self, ti: TopInfo<'tcx>, cause_span: Span) -> ObligationCause<'tcx> {
-        let code =
-            Pattern { span: ti.span, root_ty: ti.expected, origin_expr: ti.origin_expr.is_some() };
+        let code = ObligationCauseCode::Pattern {
+            span: ti.span,
+            root_ty: ti.expected,
+            origin_expr: ti.origin_expr.is_some(),
+        };
         self.cause(cause_span, code)
     }
 
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index 6370794648a..56f8d4d34f6 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -2773,19 +2773,17 @@ pub enum FailureCode {
 #[extension(pub trait ObligationCauseExt<'tcx>)]
 impl<'tcx> ObligationCause<'tcx> {
     fn as_failure_code(&self, terr: TypeError<'tcx>) -> FailureCode {
-        use self::FailureCode::*;
-        use crate::traits::ObligationCauseCode::*;
         match self.code() {
-            IfExpressionWithNoElse => Error0317,
-            MainFunctionType => Error0580,
-            CompareImplItemObligation { .. }
-            | MatchExpressionArm(_)
-            | IfExpression { .. }
-            | LetElse
-            | StartFunctionType
-            | LangFunctionType(_)
-            | IntrinsicType
-            | MethodReceiver => Error0308,
+            ObligationCauseCode::IfExpressionWithNoElse => FailureCode::Error0317,
+            ObligationCauseCode::MainFunctionType => FailureCode::Error0580,
+            ObligationCauseCode::CompareImplItemObligation { .. }
+            | ObligationCauseCode::MatchExpressionArm(_)
+            | ObligationCauseCode::IfExpression { .. }
+            | ObligationCauseCode::LetElse
+            | ObligationCauseCode::StartFunctionType
+            | ObligationCauseCode::LangFunctionType(_)
+            | ObligationCauseCode::IntrinsicType
+            | ObligationCauseCode::MethodReceiver => FailureCode::Error0308,
 
             // In the case where we have no more specific thing to
             // say, also take a look at the error code, maybe we can
@@ -2794,10 +2792,10 @@ impl<'tcx> ObligationCause<'tcx> {
                 TypeError::CyclicTy(ty)
                     if ty.is_closure() || ty.is_coroutine() || ty.is_coroutine_closure() =>
                 {
-                    Error0644
+                    FailureCode::Error0644
                 }
-                TypeError::IntrinsicCast => Error0308,
-                _ => Error0308,
+                TypeError::IntrinsicCast => FailureCode::Error0308,
+                _ => FailureCode::Error0308,
             },
         }
     }
@@ -2807,36 +2805,51 @@ impl<'tcx> ObligationCause<'tcx> {
         span: Span,
         subdiags: Vec<TypeErrorAdditionalDiags>,
     ) -> ObligationCauseFailureCode {
-        use crate::traits::ObligationCauseCode::*;
         match self.code() {
-            CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
+            ObligationCauseCode::CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
                 ObligationCauseFailureCode::MethodCompat { span, subdiags }
             }
-            CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
-                ObligationCauseFailureCode::TypeCompat { span, subdiags }
-            }
-            CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
-                ObligationCauseFailureCode::ConstCompat { span, subdiags }
-            }
-            BlockTailExpression(.., hir::MatchSource::TryDesugar(_)) => {
+            ObligationCauseCode::CompareImplItemObligation {
+                kind: ty::AssocKind::Type, ..
+            } => ObligationCauseFailureCode::TypeCompat { span, subdiags },
+            ObligationCauseCode::CompareImplItemObligation {
+                kind: ty::AssocKind::Const, ..
+            } => ObligationCauseFailureCode::ConstCompat { span, subdiags },
+            ObligationCauseCode::BlockTailExpression(.., hir::MatchSource::TryDesugar(_)) => {
                 ObligationCauseFailureCode::TryCompat { span, subdiags }
             }
-            MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => match source {
+            ObligationCauseCode::MatchExpressionArm(box MatchExpressionArmCause {
+                source, ..
+            }) => match source {
                 hir::MatchSource::TryDesugar(_) => {
                     ObligationCauseFailureCode::TryCompat { span, subdiags }
                 }
                 _ => ObligationCauseFailureCode::MatchCompat { span, subdiags },
             },
-            IfExpression { .. } => ObligationCauseFailureCode::IfElseDifferent { span, subdiags },
-            IfExpressionWithNoElse => ObligationCauseFailureCode::NoElse { span },
-            LetElse => ObligationCauseFailureCode::NoDiverge { span, subdiags },
-            MainFunctionType => ObligationCauseFailureCode::FnMainCorrectType { span },
-            StartFunctionType => ObligationCauseFailureCode::FnStartCorrectType { span, subdiags },
-            &LangFunctionType(lang_item_name) => {
+            ObligationCauseCode::IfExpression { .. } => {
+                ObligationCauseFailureCode::IfElseDifferent { span, subdiags }
+            }
+            ObligationCauseCode::IfExpressionWithNoElse => {
+                ObligationCauseFailureCode::NoElse { span }
+            }
+            ObligationCauseCode::LetElse => {
+                ObligationCauseFailureCode::NoDiverge { span, subdiags }
+            }
+            ObligationCauseCode::MainFunctionType => {
+                ObligationCauseFailureCode::FnMainCorrectType { span }
+            }
+            ObligationCauseCode::StartFunctionType => {
+                ObligationCauseFailureCode::FnStartCorrectType { span, subdiags }
+            }
+            &ObligationCauseCode::LangFunctionType(lang_item_name) => {
                 ObligationCauseFailureCode::FnLangCorrectType { span, subdiags, lang_item_name }
             }
-            IntrinsicType => ObligationCauseFailureCode::IntrinsicCorrectType { span, subdiags },
-            MethodReceiver => ObligationCauseFailureCode::MethodCorrectType { span, subdiags },
+            ObligationCauseCode::IntrinsicType => {
+                ObligationCauseFailureCode::IntrinsicCorrectType { span, subdiags }
+            }
+            ObligationCauseCode::MethodReceiver => {
+                ObligationCauseFailureCode::MethodCorrectType { span, subdiags }
+            }
 
             // In the case where we have no more specific thing to
             // say, also take a look at the error code, maybe we can
@@ -2856,22 +2869,21 @@ impl<'tcx> ObligationCause<'tcx> {
     }
 
     fn as_requirement_str(&self) -> &'static str {
-        use crate::traits::ObligationCauseCode::*;
         match self.code() {
-            CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
+            ObligationCauseCode::CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
                 "method type is compatible with trait"
             }
-            CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => {
-                "associated type is compatible with trait"
-            }
-            CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => {
-                "const is compatible with trait"
-            }
-            MainFunctionType => "`main` function has the correct type",
-            StartFunctionType => "`#[start]` function has the correct type",
-            LangFunctionType(_) => "lang item function has the correct type",
-            IntrinsicType => "intrinsic has the correct type",
-            MethodReceiver => "method receiver has the correct type",
+            ObligationCauseCode::CompareImplItemObligation {
+                kind: ty::AssocKind::Type, ..
+            } => "associated type is compatible with trait",
+            ObligationCauseCode::CompareImplItemObligation {
+                kind: ty::AssocKind::Const, ..
+            } => "const is compatible with trait",
+            ObligationCauseCode::MainFunctionType => "`main` function has the correct type",
+            ObligationCauseCode::StartFunctionType => "`#[start]` function has the correct type",
+            ObligationCauseCode::LangFunctionType(_) => "lang item function has the correct type",
+            ObligationCauseCode::IntrinsicType => "intrinsic has the correct type",
+            ObligationCauseCode::MethodReceiver => "method receiver has the correct type",
             _ => "types are compatible",
         }
     }
@@ -2882,16 +2894,21 @@ pub struct ObligationCauseAsDiagArg<'tcx>(pub ObligationCause<'tcx>);
 
 impl IntoDiagArg for ObligationCauseAsDiagArg<'_> {
     fn into_diag_arg(self) -> rustc_errors::DiagArgValue {
-        use crate::traits::ObligationCauseCode::*;
         let kind = match self.0.code() {
-            CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => "method_compat",
-            CompareImplItemObligation { kind: ty::AssocKind::Type, .. } => "type_compat",
-            CompareImplItemObligation { kind: ty::AssocKind::Const, .. } => "const_compat",
-            MainFunctionType => "fn_main_correct_type",
-            StartFunctionType => "fn_start_correct_type",
-            LangFunctionType(_) => "fn_lang_correct_type",
-            IntrinsicType => "intrinsic_correct_type",
-            MethodReceiver => "method_correct_type",
+            ObligationCauseCode::CompareImplItemObligation { kind: ty::AssocKind::Fn, .. } => {
+                "method_compat"
+            }
+            ObligationCauseCode::CompareImplItemObligation {
+                kind: ty::AssocKind::Type, ..
+            } => "type_compat",
+            ObligationCauseCode::CompareImplItemObligation {
+                kind: ty::AssocKind::Const, ..
+            } => "const_compat",
+            ObligationCauseCode::MainFunctionType => "fn_main_correct_type",
+            ObligationCauseCode::StartFunctionType => "fn_start_correct_type",
+            ObligationCauseCode::LangFunctionType(_) => "fn_lang_correct_type",
+            ObligationCauseCode::IntrinsicType => "intrinsic_correct_type",
+            ObligationCauseCode::MethodReceiver => "method_correct_type",
             _ => "other",
         }
         .into();
diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs
index 6d43011d33c..11e0d8fac3c 100644
--- a/compiler/rustc_infer/src/traits/util.rs
+++ b/compiler/rustc_infer/src/traits/util.rs
@@ -1,7 +1,7 @@
 use smallvec::smallvec;
 
 use crate::infer::outlives::components::{push_outlives_components, Component};
-use crate::traits::{self, Obligation, PredicateObligation};
+use crate::traits::{self, Obligation, ObligationCauseCode, PredicateObligation};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
 use rustc_span::symbol::Ident;
@@ -129,12 +129,14 @@ impl<'tcx> Elaboratable<'tcx> for PredicateObligation<'tcx> {
         index: usize,
     ) -> Self {
         let cause = self.cause.clone().derived_cause(parent_trait_pred, |derived| {
-            traits::ImplDerivedObligation(Box::new(traits::ImplDerivedObligationCause {
-                derived,
-                impl_or_alias_def_id: parent_trait_pred.def_id(),
-                impl_def_predicate_index: Some(index),
-                span,
-            }))
+            ObligationCauseCode::ImplDerivedObligation(Box::new(
+                traits::ImplDerivedObligationCause {
+                    derived,
+                    impl_or_alias_def_id: parent_trait_pred.def_id(),
+                    impl_def_predicate_index: Some(index),
+                    span,
+                },
+            ))
         });
         Obligation {
             cause,
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 1ae037e09a7..50b85d895ad 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -33,8 +33,6 @@ use std::hash::{Hash, Hasher};
 
 pub use self::select::{EvaluationCache, EvaluationResult, OverflowError, SelectionCache};
 
-pub use self::ObligationCauseCode::*;
-
 /// Depending on the stage of compilation, we want projection to be
 /// more or less conservative.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, HashStable, Encodable, Decodable)]
@@ -129,7 +127,7 @@ impl<'tcx> ObligationCause<'tcx> {
     }
 
     pub fn misc(span: Span, body_id: LocalDefId) -> ObligationCause<'tcx> {
-        ObligationCause::new(span, body_id, MiscObligation)
+        ObligationCause::new(span, body_id, ObligationCauseCode::MiscObligation)
     }
 
     #[inline(always)]
@@ -189,8 +187,8 @@ impl<'tcx> ObligationCause<'tcx> {
 
     pub fn to_constraint_category(&self) -> ConstraintCategory<'tcx> {
         match self.code() {
-            MatchImpl(cause, _) => cause.to_constraint_category(),
-            AscribeUserTypeProvePredicate(predicate_span) => {
+            ObligationCauseCode::MatchImpl(cause, _) => cause.to_constraint_category(),
+            ObligationCauseCode::AscribeUserTypeProvePredicate(predicate_span) => {
                 ConstraintCategory::Predicate(*predicate_span)
             }
             _ => ConstraintCategory::BoringNoLocation,
@@ -540,19 +538,22 @@ impl<'tcx> ObligationCauseCode<'tcx> {
 
     pub fn parent(&self) -> Option<(&Self, Option<ty::PolyTraitPredicate<'tcx>>)> {
         match self {
-            FunctionArgumentObligation { parent_code, .. } => Some((parent_code, None)),
-            BuiltinDerivedObligation(derived)
-            | WellFormedDerivedObligation(derived)
-            | ImplDerivedObligation(box ImplDerivedObligationCause { derived, .. }) => {
-                Some((&derived.parent_code, Some(derived.parent_trait_pred)))
+            ObligationCauseCode::FunctionArgumentObligation { parent_code, .. } => {
+                Some((parent_code, None))
             }
+            ObligationCauseCode::BuiltinDerivedObligation(derived)
+            | ObligationCauseCode::WellFormedDerivedObligation(derived)
+            | ObligationCauseCode::ImplDerivedObligation(box ImplDerivedObligationCause {
+                derived,
+                ..
+            }) => Some((&derived.parent_code, Some(derived.parent_trait_pred))),
             _ => None,
         }
     }
 
     pub fn peel_match_impls(&self) -> &Self {
         match self {
-            MatchImpl(cause, _) => cause.code(),
+            ObligationCauseCode::MatchImpl(cause, _) => cause.code(),
             _ => self,
         }
     }
diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index f92b1eb88cd..893a6428a5e 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -7,7 +7,7 @@ use rustc_infer::traits::solve::inspect::ProbeKind;
 use rustc_infer::traits::solve::{CandidateSource, GoalSource, MaybeCause};
 use rustc_infer::traits::{
     self, FulfillmentError, FulfillmentErrorCode, MismatchedProjectionTypes, Obligation,
-    ObligationCause, PredicateObligation, SelectionError, TraitEngine,
+    ObligationCause, ObligationCauseCode, PredicateObligation, SelectionError, TraitEngine,
 };
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::{self, TyCtxt};
@@ -425,17 +425,20 @@ fn derive_cause<'tcx>(
                 tcx.predicates_of(impl_def_id).instantiate_identity(tcx).iter().nth(idx)
             {
                 cause = cause.derived_cause(parent_trait_pred, |derived| {
-                    traits::ImplDerivedObligation(Box::new(traits::ImplDerivedObligationCause {
-                        derived,
-                        impl_or_alias_def_id: impl_def_id,
-                        impl_def_predicate_index: Some(idx),
-                        span,
-                    }))
+                    ObligationCauseCode::ImplDerivedObligation(Box::new(
+                        traits::ImplDerivedObligationCause {
+                            derived,
+                            impl_or_alias_def_id: impl_def_id,
+                            impl_def_predicate_index: Some(idx),
+                            span,
+                        },
+                    ))
                 })
             }
         }
         ProbeKind::TraitCandidate { source: CandidateSource::BuiltinImpl(..), result: _ } => {
-            cause = cause.derived_cause(parent_trait_pred, traits::BuiltinDerivedObligation);
+            cause = cause
+                .derived_cause(parent_trait_pred, ObligationCauseCode::BuiltinDerivedObligation);
         }
         _ => {}
     };
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 587f2f72207..0ef007e30f1 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -13,6 +13,7 @@ use super::Selection;
 use super::SelectionContext;
 use super::SelectionError;
 use super::{Normalized, NormalizedTy, ProjectionCacheEntry, ProjectionCacheKey};
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::traits::ImplSource;
 use rustc_middle::traits::ImplSourceUserDefinedData;
@@ -573,9 +574,9 @@ pub fn normalize_inherent_projection<'a, 'b, 'tcx>(
             // diagnostics which is not ideal.
             // Consider creating separate cause codes for this specific situation.
             if span.is_dummy() {
-                super::ItemObligation(alias_ty.def_id)
+                ObligationCauseCode::ItemObligation(alias_ty.def_id)
             } else {
-                super::BindingObligation(alias_ty.def_id, span)
+                ObligationCauseCode::BindingObligation(alias_ty.def_id, span)
             },
         );
 
@@ -2113,22 +2114,22 @@ fn assoc_ty_own_obligations<'cx, 'tcx>(
 
         let nested_cause = if matches!(
             obligation.cause.code(),
-            super::CompareImplItemObligation { .. }
-                | super::CheckAssociatedTypeBounds { .. }
-                | super::AscribeUserTypeProvePredicate(..)
+            ObligationCauseCode::CompareImplItemObligation { .. }
+                | ObligationCauseCode::CheckAssociatedTypeBounds { .. }
+                | ObligationCauseCode::AscribeUserTypeProvePredicate(..)
         ) {
             obligation.cause.clone()
         } else if span.is_dummy() {
             ObligationCause::new(
                 obligation.cause.span,
                 obligation.cause.body_id,
-                super::ItemObligation(obligation.predicate.def_id),
+                ObligationCauseCode::ItemObligation(obligation.predicate.def_id),
             )
         } else {
             ObligationCause::new(
                 obligation.cause.span,
                 obligation.cause.body_id,
-                super::BindingObligation(obligation.predicate.def_id, span),
+                ObligationCauseCode::BindingObligation(obligation.predicate.def_id, span),
             )
         };
         nested.push(Obligation::with_depth(
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 22e0ee38344..3746e56b7c9 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -11,6 +11,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::lang_items::LangItem;
 use rustc_infer::infer::HigherRankedType;
 use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::traits::{BuiltinImplSource, SignatureMismatchData};
 use rustc_middle::ty::{
     self, GenericArgs, GenericArgsRef, GenericParamDefKind, ToPolyTraitRef, ToPredicate,
@@ -25,10 +26,9 @@ use crate::traits::vtable::{
     VtblSegment,
 };
 use crate::traits::{
-    BuiltinDerivedObligation, ImplDerivedObligation, ImplDerivedObligationCause, ImplSource,
-    ImplSourceUserDefinedData, Normalized, Obligation, ObligationCause, PolyTraitObligation,
-    PredicateObligation, Selection, SelectionError, SignatureMismatch, TraitNotObjectSafe,
-    TraitObligation, Unimplemented,
+    ImplDerivedObligationCause, ImplSource, ImplSourceUserDefinedData, Normalized, Obligation,
+    ObligationCause, PolyTraitObligation, PredicateObligation, Selection, SelectionError,
+    SignatureMismatch, TraitNotObjectSafe, TraitObligation, Unimplemented,
 };
 
 use super::BuiltinImplConditions;
@@ -275,7 +275,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 bug!("obligation {:?} had matched a builtin impl but now doesn't", obligation);
             };
 
-            let cause = obligation.derived_cause(BuiltinDerivedObligation);
+            let cause = obligation.derived_cause(ObligationCauseCode::BuiltinDerivedObligation);
             self.collect_predicates_for_types(
                 obligation.param_env,
                 cause,
@@ -435,7 +435,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     ) -> Vec<PredicateObligation<'tcx>> {
         debug!(?nested, "vtable_auto_impl");
         ensure_sufficient_stack(|| {
-            let cause = obligation.derived_cause(BuiltinDerivedObligation);
+            let cause = obligation.derived_cause(ObligationCauseCode::BuiltinDerivedObligation);
 
             let poly_trait_ref = obligation.predicate.to_poly_trait_ref();
             let trait_ref = self.infcx.enter_forall_and_leak_universe(poly_trait_ref);
@@ -723,7 +723,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         let mut nested =
             self.equate_trait_refs(obligation.with(tcx, placeholder_predicate), trait_ref)?;
-        let cause = obligation.derived_cause(BuiltinDerivedObligation);
+        let cause = obligation.derived_cause(ObligationCauseCode::BuiltinDerivedObligation);
 
         // Confirm the `type Output: Sized;` bound that is present on `FnOnce`
         let output_ty = self.infcx.enter_forall_and_leak_universe(sig.output());
@@ -1381,7 +1381,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let self_ty = obligation.self_ty().map_bound(|ty| self.infcx.shallow_resolve(ty));
 
         let mut nested = vec![];
-        let cause = obligation.derived_cause(BuiltinDerivedObligation);
+        let cause = obligation.derived_cause(ObligationCauseCode::BuiltinDerivedObligation);
 
         // If we have a custom `impl const Drop`, then
         // first check it like a regular impl candidate.
@@ -1396,7 +1396,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             debug!(?args, "impl args");
 
             let cause = obligation.derived_cause(|derived| {
-                ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
+                ObligationCauseCode::ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
                     derived,
                     impl_or_alias_def_id: impl_def_id,
                     impl_def_predicate_index: None,
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index dc005982695..f9246d22bfe 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -13,9 +13,9 @@ use super::util;
 use super::util::closure_trait_ref_and_return_type;
 use super::wf;
 use super::{
-    ImplDerivedObligation, ImplDerivedObligationCause, Normalized, Obligation, ObligationCause,
-    ObligationCauseCode, Overflow, PolyTraitObligation, PredicateObligation, Selection,
-    SelectionError, SelectionResult, TraitQueryMode,
+    ImplDerivedObligationCause, Normalized, Obligation, ObligationCause, ObligationCauseCode,
+    Overflow, PolyTraitObligation, PredicateObligation, Selection, SelectionError, SelectionResult,
+    TraitQueryMode,
 };
 
 use crate::infer::{InferCtxt, InferOk, TypeFreshener};
@@ -2771,12 +2771,14 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                     cause.clone()
                 } else {
                     cause.clone().derived_cause(parent_trait_pred, |derived| {
-                        ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
-                            derived,
-                            impl_or_alias_def_id: def_id,
-                            impl_def_predicate_index: Some(index),
-                            span,
-                        }))
+                        ObligationCauseCode::ImplDerivedObligation(Box::new(
+                            ImplDerivedObligationCause {
+                                derived,
+                                impl_or_alias_def_id: def_id,
+                                impl_def_predicate_index: Some(index),
+                                span,
+                            },
+                        ))
                     })
                 };
             let clause = normalize_with_depth_to(
diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs
index 28ee76f7145..44c70f2be00 100644
--- a/compiler/rustc_trait_selection/src/traits/wf.rs
+++ b/compiler/rustc_trait_selection/src/traits/wf.rs
@@ -2,6 +2,7 @@ use crate::infer::InferCtxt;
 use crate::traits;
 use rustc_hir as hir;
 use rustc_hir::lang_items::LangItem;
+use rustc_infer::traits::ObligationCauseCode;
 use rustc_middle::ty::{
     self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
 };
@@ -333,7 +334,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
             return self.out;
         }
 
-        let cause = self.cause(traits::WellFormed(None));
+        let cause = self.cause(ObligationCauseCode::WellFormed(None));
         let param_env = self.param_env;
         let mut obligations = Vec::with_capacity(self.out.len());
         for mut obligation in self.out {
@@ -485,7 +486,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                 &mut traits::SelectionContext::new(self.infcx),
                 self.param_env,
                 data,
-                self.cause(traits::WellFormed(None)),
+                self.cause(ObligationCauseCode::WellFormed(None)),
                 self.recursion_depth,
                 &mut self.out,
             );
@@ -498,7 +499,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 
     fn compute_projection_args(&mut self, args: GenericArgsRef<'tcx>) {
         let tcx = self.tcx();
-        let cause = self.cause(traits::WellFormed(None));
+        let cause = self.cause(ObligationCauseCode::WellFormed(None));
         let param_env = self.param_env;
         let depth = self.recursion_depth;
 
@@ -565,9 +566,9 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         iter::zip(predicates, origins.into_iter().rev())
             .map(|((pred, span), origin_def_id)| {
                 let code = if span.is_dummy() {
-                    traits::ItemObligation(origin_def_id)
+                    ObligationCauseCode::ItemObligation(origin_def_id)
                 } else {
-                    traits::BindingObligation(origin_def_id, span)
+                    ObligationCauseCode::BindingObligation(origin_def_id, span)
                 };
                 let cause = self.cause(code);
                 traits::Obligation::with_depth(
@@ -626,7 +627,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 
             self.out.reserve(implicit_bounds.len());
             for implicit_bound in implicit_bounds {
-                let cause = self.cause(traits::ObjectTypeBound(ty, explicit_bound));
+                let cause = self.cause(ObligationCauseCode::ObjectTypeBound(ty, explicit_bound));
                 let outlives =
                     ty::Binder::dummy(ty::OutlivesPredicate(explicit_bound, implicit_bound));
                 self.out.push(traits::Obligation::with_depth(
@@ -644,7 +645,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
     type Result = ();
 
-    fn visit_ty(&mut self, t: <TyCtxt<'tcx> as ty::Interner>::Ty) -> Self::Result {
+    fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
         debug!("wf bounds for t={:?} t.kind={:#?}", t, t.kind());
 
         let tcx = self.tcx();
@@ -673,22 +674,22 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
             ty::Infer(ty::FloatVar(_)) => {}
 
             ty::Slice(subty) => {
-                self.require_sized(subty, traits::SliceOrArrayElem);
+                self.require_sized(subty, ObligationCauseCode::SliceOrArrayElem);
             }
 
             ty::Array(subty, _) => {
-                self.require_sized(subty, traits::SliceOrArrayElem);
+                self.require_sized(subty, ObligationCauseCode::SliceOrArrayElem);
                 // Note that we handle the len is implicitly checked while walking `arg`.
             }
 
             ty::Pat(subty, _) => {
-                self.require_sized(subty, traits::MiscObligation);
+                self.require_sized(subty, ObligationCauseCode::MiscObligation);
             }
 
             ty::Tuple(tys) => {
                 if let Some((_last, rest)) = tys.split_last() {
                     for &elem in rest {
-                        self.require_sized(elem, traits::TupleElem);
+                        self.require_sized(elem, ObligationCauseCode::TupleElem);
                     }
                 }
             }
@@ -728,7 +729,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
             ty::Ref(r, rty, _) => {
                 // WfReference
                 if !r.has_escaping_bound_vars() && !rty.has_escaping_bound_vars() {
-                    let cause = self.cause(traits::ReferenceOutlivesReferent(t));
+                    let cause = self.cause(ObligationCauseCode::ReferenceOutlivesReferent(t));
                     self.out.push(traits::Obligation::with_depth(
                         tcx,
                         cause,
@@ -825,7 +826,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                     if let Some(principal) = data.principal_def_id() {
                         self.out.push(traits::Obligation::with_depth(
                             tcx,
-                            self.cause(traits::WellFormed(None)),
+                            self.cause(ObligationCauseCode::WellFormed(None)),
                             self.recursion_depth,
                             self.param_env,
                             ty::Binder::dummy(ty::PredicateKind::ObjectSafe(principal)),
@@ -847,7 +848,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
             // See also the comment on `fn obligations`, describing "livelock"
             // prevention, which happens before this can be reached.
             ty::Infer(_) => {
-                let cause = self.cause(traits::WellFormed(None));
+                let cause = self.cause(ObligationCauseCode::WellFormed(None));
                 self.out.push(traits::Obligation::with_depth(
                     tcx,
                     cause,
@@ -863,7 +864,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
         t.super_visit_with(self)
     }
 
-    fn visit_const(&mut self, c: <TyCtxt<'tcx> as ty::Interner>::Const) -> Self::Result {
+    fn visit_const(&mut self, c: ty::Const<'tcx>) -> Self::Result {
         let tcx = self.tcx();
 
         match c.kind() {
@@ -875,7 +876,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                     let predicate = ty::Binder::dummy(ty::PredicateKind::Clause(
                         ty::ClauseKind::ConstEvaluatable(c),
                     ));
-                    let cause = self.cause(traits::WellFormed(None));
+                    let cause = self.cause(ObligationCauseCode::WellFormed(None));
                     self.out.push(traits::Obligation::with_depth(
                         tcx,
                         cause,
@@ -886,7 +887,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                 }
             }
             ty::ConstKind::Infer(_) => {
-                let cause = self.cause(traits::WellFormed(None));
+                let cause = self.cause(ObligationCauseCode::WellFormed(None));
 
                 self.out.push(traits::Obligation::with_depth(
                     tcx,
@@ -909,7 +910,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                 let predicate = ty::Binder::dummy(ty::PredicateKind::Clause(
                     ty::ClauseKind::ConstEvaluatable(c),
                 ));
-                let cause = self.cause(traits::WellFormed(None));
+                let cause = self.cause(ObligationCauseCode::WellFormed(None));
                 self.out.push(traits::Obligation::with_depth(
                     tcx,
                     cause,
@@ -933,7 +934,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
         c.super_visit_with(self)
     }
 
-    fn visit_predicate(&mut self, _p: <TyCtxt<'tcx> as ty::Interner>::Predicate) -> Self::Result {
+    fn visit_predicate(&mut self, _p: ty::Predicate<'tcx>) -> Self::Result {
         bug!("predicate should not be checked for well-formedness");
     }
 }