Correct the wildcard tests for import prefixes. (#3866)

An unrelated fix, #3865, revealed that
the wildcard-variables experiment was not actually enabled in tests; the SDK
constraint used in test packages needs to be '^3.6.0'. With that fix, there are
some questions about how much dartdoc should be doing to keep wildcards
"non-binding" and how much the analyzer should be doing. So that is raised in
#3769 (comment).

lib/src/model/comment_referable.dart

@@ -7,12 +7,14 @@ library;
 
 import 'dart:core';
 
+import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/scope.dart';
 import 'package:collection/collection.dart';
 import 'package:dartdoc/src/model/library.dart';
 import 'package:dartdoc/src/model/model_element.dart';
 import 'package:dartdoc/src/model/nameable.dart';
+import 'package:dartdoc/src/model/prefix.dart';
 import 'package:meta/meta.dart';
 
 class _ReferenceChildrenLookup {
@@ -55,6 +57,12 @@ mixin CommentReferable implements Nameable {
       // First attempt: Ask analyzer's `Scope.lookup` API.
       var result = _lookupViaScope(referenceLookup, filter: filter);
       if (result != null) {
+        if (result is Prefix &&
+            result.name == '_' &&
+            library!.element.featureSet.isEnabled(Feature.wildcard_variables)) {
+          // A wildcard import prefix is non-binding.
+          continue;
+        }
         return result;
       }
 

lib/src/model/library.dart

@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/scope.dart';
 import 'package:analyzer/source/line_info.dart';
@@ -442,6 +443,11 @@ class Library extends ModelElement
     // ambiguous.  dart-lang/dartdoc#2683.
     for (var MapEntry(key: prefix, value: libraries)
         in _prefixToLibrary.entries) {
+      if (prefix == '_' &&
+          element.featureSet.isEnabled(Feature.wildcard_variables)) {
+        // A wildcard import prefix is non-binding.
+        continue;
+      }
       referenceChildrenBuilder.putIfAbsent(prefix, () => libraries.first);
     }
     return referenceChildrenBuilder;

test/dartdoc_test_base.dart

@@ -41,7 +41,7 @@ abstract class DartdocTestBase {
 
   String get dartCoreUrlPrefix => 'https://api.dart.dev/stable/3.2.0/dart-core';
 
-  String get sdkConstraint => '>=3.3.0 <4.0.0';
+  String get sdkConstraint => '>=3.6.0 <4.0.0';
 
   List<String> get experiments => ['wildcard-variables'];
 

test/prefixes_test.dart

@@ -36,7 +36,6 @@ int x = 0;
     );
   }
 
-  @FailingTest(issue: 'https://github.com/dart-lang/dartdoc/issues/3769')
   void test_referenced_wildcard() async {
     var library = await bootPackageWithLibrary(
       '''