Remove some more usages of guess_head_span

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -823,10 +823,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
                     ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
                         let found_kind = self.closure_kind(closure_substs).unwrap();
-                        let closure_span =
-                            self.tcx.sess.source_map().guess_head_span(
-                                self.tcx.hir().span_if_local(closure_def_id).unwrap(),
-                            );
+                        let closure_span = self.tcx.def_span(closure_def_id);
                         let mut err = struct_span_err!(
                             self.tcx.sess,
                             closure_span,
@@ -951,9 +948,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     _ => None,
                 };
 
-                let found_span = found_did
-                    .and_then(|did| self.tcx.hir().span_if_local(did))
-                    .map(|sp| self.tcx.sess.source_map().guess_head_span(sp)); // the sp could be a closure
+                let found_span = found_did.and_then(|did| self.tcx.hir().span_if_local(did));
 
                 if self.reported_closure_mismatch.borrow().contains(&(span, found_span)) {
                     // We check closures twice, with obligations flowing in different directions,

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1543,7 +1543,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             ty::Generator(..) => "generator",
             _ => "function",
         };
-        let span = self.tcx.sess.source_map().guess_head_span(span);
         let mut err = struct_span_err!(
             self.tcx.sess,
             span,

compiler/rustc_typeck/src/check/compare_method.rs

@@ -171,14 +171,7 @@ fn compare_predicate_entailment<'tcx>(
     let trait_m_predicates = tcx.predicates_of(trait_m.def_id);
 
     // Check region bounds.
-    check_region_bounds_on_impl_item(
-        tcx,
-        impl_m_span,
-        impl_m,
-        trait_m,
-        &trait_m_generics,
-        &impl_m_generics,
-    )?;
+    check_region_bounds_on_impl_item(tcx, impl_m, trait_m, &trait_m_generics, &impl_m_generics)?;
 
     // Create obligations for each predicate declared by the impl
     // definition in the context of the trait's parameter
@@ -410,7 +403,6 @@ fn compare_predicate_entailment<'tcx>(
 
 fn check_region_bounds_on_impl_item<'tcx>(
     tcx: TyCtxt<'tcx>,
-    span: Span,
     impl_m: &ty::AssocItem,
     trait_m: &ty::AssocItem,
     trait_generics: &ty::Generics,
@@ -436,23 +428,25 @@ fn check_region_bounds_on_impl_item<'tcx>(
     // are zero. Since I don't quite know how to phrase things at
     // the moment, give a kind of vague error message.
     if trait_params != impl_params {
-        let item_kind = assoc_item_kind_str(impl_m);
-        let span = impl_m
-            .def_id
-            .as_local()
-            .and_then(|did| tcx.hir().get_generics(did))
-            .map_or(span, |g| g.span);
-        let generics_span = tcx.hir().span_if_local(trait_m.def_id).map(|sp| {
-            trait_m
-                .def_id
-                .as_local()
-                .and_then(|did| tcx.hir().get_generics(did))
-                .map_or(sp, |g| g.span)
-        });
+        let span = tcx
+            .hir()
+            .get_generics(impl_m.def_id.expect_local())
+            .expect("expected impl item to have generics or else we can't compare them")
+            .span;
+        let generics_span = if let Some(local_def_id) = trait_m.def_id.as_local() {
+            Some(
+                tcx.hir()
+                    .get_generics(local_def_id)
+                    .expect("expected trait item to have generics or else we can't compare them")
+                    .span,
+            )
+        } else {
+            None
+        };
 
         let reported = tcx.sess.emit_err(LifetimesOrBoundsMismatchOnTrait {
             span,
-            item_kind,
+            item_kind: assoc_item_kind_str(impl_m),
             ident: impl_m.ident(tcx),
             generics_span,
         });
@@ -1201,7 +1195,6 @@ fn compare_type_predicate_entailment<'tcx>(
 
     check_region_bounds_on_impl_item(
         tcx,
-        impl_ty_span,
         impl_ty,
         trait_ty,
         &trait_ty_generics,