Expose current span to type equality checking in nll

compiler/rustc_borrowck/src/type_check/relate_tys.rs

@@ -3,6 +3,7 @@ use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::{self, Const, Ty};
+use rustc_span::{Span, DUMMY_SP};
 use rustc_trait_selection::traits::query::Fallible;
 
 use crate::constraints::OutlivesConstraint;
@@ -63,6 +64,13 @@ impl<'me, 'bccx, 'tcx> NllTypeRelatingDelegate<'me, 'bccx, 'tcx> {
 }
 
 impl<'tcx> TypeRelatingDelegate<'tcx> for NllTypeRelatingDelegate<'_, '_, 'tcx> {
+    fn span(&self) -> Span {
+        match self.locations {
+            Locations::All(span) => span,
+            Locations::Single(_) => DUMMY_SP,
+        }
+    }
+
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
         self.type_checker.param_env
     }

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

@@ -26,6 +26,7 @@ use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::relate::TypeRelation;
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
 use rustc_middle::ty::{self, BoundVar, Const, ToPredicate, Ty, TyCtxt};
+use rustc_span::Span;
 use std::fmt::Debug;
 use std::iter;
 
@@ -631,6 +632,10 @@ struct QueryTypeRelatingDelegate<'a, 'tcx> {
 }
 
 impl<'tcx> TypeRelatingDelegate<'tcx> for QueryTypeRelatingDelegate<'_, 'tcx> {
+    fn span(&self) -> Span {
+        self.cause.span
+    }
+
     fn param_env(&self) -> ty::ParamEnv<'tcx> {
         self.param_env
     }

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -29,6 +29,7 @@ use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::fold::{TypeFoldable, TypeVisitor};
 use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
 use rustc_middle::ty::{self, InferConst, Ty, TyCtxt};
+use rustc_span::Span;
 use std::fmt::Debug;
 use std::ops::ControlFlow;
 
@@ -75,6 +76,7 @@ where
 
 pub trait TypeRelatingDelegate<'tcx> {
     fn param_env(&self) -> ty::ParamEnv<'tcx>;
+    fn span(&self) -> Span;
 
     /// Push a constraint `sup: sub` -- this constraint must be
     /// satisfied for the two types to be related. `sub` and `sup` may