improve method invocation and string interpolation suggestions

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

Index: pkg/analysis_server/lib/src/services/completion/imported_computer.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/imported_computer.dart b/pkg/analysis_server/lib/src/services/completion/imported_computer.dart
index 3e8a85518cc278828eee6f609cae1cd25452013b..24ae17476f5fb32734d9286387b207a609281e14 100644
--- a/pkg/analysis_server/lib/src/services/completion/imported_computer.dart
+++ b/pkg/analysis_server/lib/src/services/completion/imported_computer.dart
@@ -125,6 +125,15 @@ class _ImportedVisitor extends GeneralizingAstVisitor<Future<bool>> {
   }
 
   @override
+  Future<bool> visitMethodInvocation(MethodInvocation node) {
+    Token period = node.period;
+    if (period == null || request.offset <= period.offset) {
+      return _addImportedElementSuggestions();
+    }
+    return new Future.value(false);
+  }
+
+  @override
   Future<bool> visitNode(AstNode node) {
     return new Future.value(false);
   }