fix code completion in string literals

pkg/analysis_server/lib/src/services/completion/optype.dart

Index: pkg/analysis_server/lib/src/services/completion/optype.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/optype.dart b/pkg/analysis_server/lib/src/services/completion/optype.dart
index 3a6d6ef12dd042f54e0af30bf27cb6d6fd7211e7..efaa8fd6a3cb1a79d7daf347ee6f03707f0aa297 100644
--- a/pkg/analysis_server/lib/src/services/completion/optype.dart
+++ b/pkg/analysis_server/lib/src/services/completion/optype.dart
@@ -378,6 +378,12 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
   }
 
   @override
+  void visitListLiteral(ListLiteral node) {
+    optype.includeReturnValueSuggestions = true;
+    optype.includeTypeNameSuggestions = true;
+  }
+
+  @override
   void visitMethodDeclaration(MethodDeclaration node) {
   }