Implement completion in WithDirective.

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

Index: pkg/analysis_server/lib/src/services/completion/dart/optype.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/optype.dart b/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
index c9954d5caea2741268c9f065248b9c4eb096fc1d..e73413cd9ac7c66e0702a9c7b6144091ed084d8b 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/optype.dart
@@ -906,6 +906,11 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
     }
   }
 
+  @override
+  void visitWithClause(WithClause node) {
+    optype.includeTypeNameSuggestions = true;
+  }
+
   bool _isEntityPrevTokenSynthetic() {
     Object entity = this.entity;
     if (entity is AstNode && entity.beginToken.previous?.isSynthetic ?? false) {