suggest imported functions in argument list

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 d16b80d4f4dc74e01b6572ee1aaaa296c6de2529..2cfbc814ab775d626a24298662a7411ad2789884 100644
--- a/pkg/analysis_server/lib/src/services/completion/imported_computer.dart
+++ b/pkg/analysis_server/lib/src/services/completion/imported_computer.dart
@@ -48,6 +48,11 @@ class _ImportedVisitor extends GeneralizingAstVisitor<Future<bool>> {
   _ImportedVisitor(this.request);
 
   @override
+  Future<bool> visitArgumentList(ArgumentList node) {
+    return _addImportedElementSuggestions(node, excludeVoidReturn: true);
+  }
+
+  @override
   Future<bool> visitBlock(Block node) {
     return _addImportedElementSuggestions(node);
   }