[wildcards] avoid_unused_constructor_parameters wildcard test

Test to ensure that `avoid_unused_constructor_parameters` doesn't overreport in the presence of an unused wildcard param.

(Note that underscores are ignored pre-wildcards too and this ensures that that behavior is preserved too.)

Fixes: dart-lang/linter#4995

Change-Id: I13ef73eb28cf2501ed292dd3c56c9933a8feefa9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/370540
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Auto-Submit: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/linter/test/rule_test_support.dart

@@ -177,7 +177,7 @@ class PubPackageResolutionTest extends _ContextResolutionTest {
 
   bool get dumpAstOnFailures => true;
 
-  List<String> get experiments => ['macros'];
+  List<String> get experiments => ['macros', 'wildcard-variables'];
 
   List<String> get lintRules => _lintRules;
 

pkg/linter/test/rules/avoid_unused_constructor_parameters_test.dart

@@ -63,6 +63,25 @@ class A {
 class B extends A {
   B(super.a, super.b);
 }
+''');
+  }
+
+  test_wildcardParam() async {
+    await assertNoDiagnostics(r'''
+class C {
+ C(int _);
+}
+''');
+  }
+
+  test_wildcardParam_preWildcards() async {
+    await assertNoDiagnostics(r'''
+// @dart = 3.4
+// (pre wildcard-variables)
+
+class C {
+ C(int _);
+}
 ''');
   }
 }