Completions with exact prefix should be prioritized - fixes #23099

pkg/analysis_server/test/services/completion/local_reference_contributor_test.dart

Index: pkg/analysis_server/test/services/completion/local_reference_contributor_test.dart
diff --git a/pkg/analysis_server/test/services/completion/local_reference_contributor_test.dart b/pkg/analysis_server/test/services/completion/local_reference_contributor_test.dart
index cb29f9782f8b7bc06454e9b3d3d8e53fc80b2e20..94c07173d7e315ad49524be6c37911331580887a 100644
--- a/pkg/analysis_server/test/services/completion/local_reference_contributor_test.dart
+++ b/pkg/analysis_server/test/services/completion/local_reference_contributor_test.dart
@@ -793,6 +793,20 @@ class B extends A {m() {^}}
     assertSuggestMethod('m', 'B', null, relevance: DART_RELEVANCE_LOCAL_METHOD);
   }
 
+  test_prioritization_private() {
+    addTestSource('main() {var ab; var _ab; _^}');
+    expect(computeFast(), isTrue);
+    assertSuggestLocalVariable('ab', null);
+    assertSuggestLocalVariable('_ab', null);
+  }
+
+  test_prioritization_public() {
+    addTestSource('main() {var ab; var _ab; a^}');
+    expect(computeFast(), isTrue);
+    assertSuggestLocalVariable('ab', null);
+    assertSuggestLocalVariable('_ab', null, relevance: DART_RELEVANCE_DEFAULT);
+  }
+
   test_shadowed_name() {
     addTestSource('var a; class A { var a; m() { ^ } }');
     expect(computeFast(), isTrue);