Add to_constraint_category to ObligationCause and SubregionOrigin

compiler/rustc_infer/src/infer/canonical/query_response.rs

@@ -249,7 +249,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
         // the original values `v_o` that was canonicalized into a
         // variable...
 
-        let constraint_category = ConstraintCategory::BoringNoLocation;
+        let constraint_category = cause.to_constraint_category();
 
         for (index, original_value) in original_values.var_values.iter().enumerate() {
             // ...with the value `v_r` of that variable from the query.
@@ -643,7 +643,7 @@ pub fn make_query_region_constraints<'tcx>(
 
     let outlives: Vec<_> = constraints
         .iter()
-        .map(|(k, _)| {
+        .map(|(k, origin)| {
             let constraint = ty::Binder::dummy(match *k {
                 // Swap regions because we are going from sub (<=) to outlives
                 // (>=).
@@ -660,7 +660,7 @@ pub fn make_query_region_constraints<'tcx>(
                 Constraint::RegSubReg(r1, r2) => ty::OutlivesPredicate(r2.into(), r1),
             });
 
-            (constraint, ConstraintCategory::BoringNoLocation)
+            (constraint, origin.to_constraint_category())
         })
         .chain(
             outlives_obligations

compiler/rustc_infer/src/infer/mod.rs

@@ -20,6 +20,7 @@ use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
 use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue};
 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType};
 use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
+use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::traits::select;
 use rustc_middle::ty::abstract_const::{AbstractConst, FailureKind};
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
@@ -422,6 +423,15 @@ pub enum SubregionOrigin<'tcx> {
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 static_assert_size!(SubregionOrigin<'_>, 32);
 
+impl<'tcx> SubregionOrigin<'tcx> {
+    pub fn to_constraint_category(&self) -> ConstraintCategory<'tcx> {
+        match self {
+            Self::Subtype(type_trace) => type_trace.cause.to_constraint_category(),
+            _ => ConstraintCategory::BoringNoLocation,
+        }
+    }
+}
+
 /// Times when we replace late-bound regions with variables:
 #[derive(Clone, Copy, Debug)]
 pub enum LateBoundRegionConversionTime {

compiler/rustc_infer/src/infer/outlives/obligations.rs

@@ -164,7 +164,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
 
             let outlives =
                 &mut TypeOutlives::new(self, self.tcx, &region_bound_pairs, None, param_env);
-            let category = ConstraintCategory::BoringNoLocation;
+            let category = origin.to_constraint_category();
             outlives.type_must_outlive(origin, sup_type, sub_region, category);
         }
     }
@@ -394,7 +394,7 @@ where
         if approx_env_bounds.is_empty() && trait_bounds.is_empty() && needs_infer {
             debug!("projection_must_outlive: no declared bounds");
 
-            let constraint = ConstraintCategory::BoringNoLocation;
+            let constraint = origin.to_constraint_category();
             for k in projection_ty.substs {
                 match k.unpack() {
                     GenericArgKind::Lifetime(lt) => {
@@ -444,7 +444,7 @@ where
             let unique_bound = trait_bounds[0];
             debug!("projection_must_outlive: unique trait bound = {:?}", unique_bound);
             debug!("projection_must_outlive: unique declared bound appears in trait ref");
-            let category = ConstraintCategory::BoringNoLocation;
+            let category = origin.to_constraint_category();
             self.delegate.push_sub_region_constraint(origin, region, unique_bound, category);
             return;
         }

compiler/rustc_middle/src/traits/mod.rs

@@ -10,6 +10,7 @@ mod structural_impls;
 pub mod util;
 
 use crate::infer::canonical::Canonical;
+use crate::mir::ConstraintCategory;
 use crate::ty::abstract_const::NotConstEvaluatable;
 use crate::ty::subst::SubstsRef;
 use crate::ty::{self, AdtKind, Ty, TyCtxt};
@@ -183,6 +184,13 @@ impl<'tcx> ObligationCause<'tcx> {
             variant(DerivedObligationCause { parent_trait_pred, parent_code: self.code }).into();
         self
     }
+
+    pub fn to_constraint_category(&self) -> ConstraintCategory<'tcx> {
+        match self.code() {
+            MatchImpl(cause, _) => cause.to_constraint_category(),
+            _ => ConstraintCategory::BoringNoLocation,
+        }
+    }
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]