fix missing returns in lambdas

Change-Id: I5005ffc057749468844d47e8e5c195871586bd57
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/103601
Reviewed-by: Dan Rubel <danrubel@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>
diff --git a/pkg/analysis_server/lib/src/edit/fix/non_nullable_fix.dart b/pkg/analysis_server/lib/src/edit/fix/non_nullable_fix.dart
index 61d3984..62161e4 100644
--- a/pkg/analysis_server/lib/src/edit/fix/non_nullable_fix.dart
+++ b/pkg/analysis_server/lib/src/edit/fix/non_nullable_fix.dart
@@ -105,6 +105,7 @@
             content = '''
 
     - non-nullable''';
+            return null;
           },
         );
       }
diff --git a/pkg/analyzer/lib/src/summary2/builder/source_library_builder.dart b/pkg/analyzer/lib/src/summary2/builder/source_library_builder.dart
index c411c79..2845328 100644
--- a/pkg/analyzer/lib/src/summary2/builder/source_library_builder.dart
+++ b/pkg/analyzer/lib/src/summary2/builder/source_library_builder.dart
@@ -65,6 +65,7 @@
             var nameList = node.hiddenNames.map((i) => i.name).toList();
             return Combinator.hide(nameList);
           }
+          return null;
         }).toList();
 
         var exported = linker.builders[uri];