Fix nits

Author: IntQuant

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs

@@ -333,17 +333,15 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             leading_ellipsis,
         );
 
-        let diag = TraitPlaceholderMismatch {
+        self.tcx().sess.create_err(TraitPlaceholderMismatch {
             span,
             satisfy_span,
             where_span,
             dup_span,
             def_id,
             trait_def_id: self.tcx().def_path_str(trait_def_id),
             actual_impl_expl_notes,
-        };
-
-        self.tcx().sess.create_err(diag)
+        })
     }
 
     /// Add notes with details about the expected and actual trait refs, with attention to cases

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -63,7 +63,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                         AssocItemContainer::ImplContainer => (false, String::new()),
                     };
 
-                    let diag = ButCallingIntroduces {
+                    let mut err = self.tcx().sess.create_err(ButCallingIntroduces {
                         param_ty_span: param.param_ty_span,
                         cause_span: cause.span,
                         has_param_name: simple_ident.is_some(),
@@ -73,8 +73,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                         assoc_item: ctxt.assoc_item.name,
                         has_impl_path,
                         impl_path,
-                    };
-                    let mut err = self.tcx().sess.create_err(diag);
+                    });
                     if self.find_impl_on_dyn_trait(&mut err, param.param_ty, &ctxt) {
                         let reported = err.emit();
                         return Some(reported);