prefer_const_constructors_in_immutables: simplify visitConstructorDeclaration override (#4254)

Author: srawlins

lib/src/rules/prefer_const_constructors_in_immutables.dart

@@ -82,19 +82,19 @@ class _Visitor extends SimpleAstVisitor<void> {
   @override
   void visitConstructorDeclaration(ConstructorDeclaration node) {
     var element = node.declaredElement;
-    if (element == null) {
-      return;
-    }
+    if (element == null) return;
+    if (element.isConst) return;
+    if (node.body is! EmptyFunctionBody) return;
+    if (element.enclosingElement.mixins.isNotEmpty) return;
+    if (!_hasImmutableAnnotation(element.enclosingElement)) return;
     var isRedirected =
         element.isFactory && element.redirectedConstructor != null;
-    if (node.body is EmptyFunctionBody &&
-        !element.isConst &&
-        !_hasMixin(element.enclosingElement) &&
-        _hasImmutableAnnotation(element.enclosingElement) &&
-        (isRedirected && (element.redirectedConstructor?.isConst ?? false) ||
-            (!isRedirected &&
-                _hasConstConstructorInvocation(node) &&
-                context.canBeConstConstructor(node)))) {
+    if (isRedirected && (element.redirectedConstructor?.isConst ?? false)) {
+      rule.reportLintForToken(node.firstTokenAfterCommentAndMetadata);
+    }
+    if (!isRedirected &&
+        _hasConstConstructorInvocation(node) &&
+        context.canBeConstConstructor(node)) {
       rule.reportLintForToken(node.firstTokenAfterCommentAndMetadata);
     }
   }
@@ -105,26 +105,27 @@ class _Visitor extends SimpleAstVisitor<void> {
       return false;
     }
     var clazz = declaredElement.enclosingElement;
-    // construct with super
-    var superInvocation = node.initializers
-            .firstWhereOrNull((e) => e is SuperConstructorInvocation)
-        as SuperConstructorInvocation?;
+    // Constructor with super-initializer.
+    var superInvocation =
+        node.initializers.whereType<SuperConstructorInvocation>().firstOrNull;
     if (superInvocation != null) {
       return superInvocation.staticElement?.isConst ?? false;
     }
-    // construct with this
+    // Constructor with 'this' redirecting initializer.
     var redirectInvocation = node.initializers
-            .firstWhereOrNull((e) => e is RedirectingConstructorInvocation)
-        as RedirectingConstructorInvocation?;
+        .whereType<RedirectingConstructorInvocation>()
+        .firstOrNull;
     if (redirectInvocation != null) {
       return redirectInvocation.staticElement?.isConst ?? false;
     }
-    // construct with implicit super()
+    // Constructor with implicit `super()` call.
     var supertype = clazz.supertype;
     return supertype != null &&
         supertype.constructors.firstWhere((e) => e.name.isEmpty).isConst;
   }
 
+  /// Whether [clazz] or any of it's super-types are annotated with
+  /// `@immutable`.
   bool _hasImmutableAnnotation(InterfaceElement clazz) {
     var selfAndInheritedClasses = _getSelfAndSuperClasses(clazz);
     for (var cls in selfAndInheritedClasses) {
@@ -133,8 +134,6 @@ class _Visitor extends SimpleAstVisitor<void> {
     return false;
   }
 
-  bool _hasMixin(InterfaceElement clazz) => clazz.mixins.isNotEmpty;
-
   static List<InterfaceElement> _getSelfAndSuperClasses(InterfaceElement self) {
     InterfaceElement? current = self;
     var seenElements = <InterfaceElement>{};

test/integration/prefer_const_constructors_in_immutables.dart

@@ -19,8 +19,6 @@ import 'integration/avoid_web_libraries_in_flutter.dart'
     as avoid_web_libraries_in_flutter;
 import 'integration/close_sinks.dart' as close_sinks;
 import 'integration/exhaustive_cases.dart' as exhaustive_cases;
-import 'integration/prefer_const_constructors_in_immutables.dart'
-    as prefer_const_constructors_in_immutables;
 import 'integration/public_member_api_docs.dart' as public_member_api_docs;
 import 'integration/sort_pub_dependencies.dart' as sort_pub_dependencies;
 import 'integration/use_build_context_synchronously.dart'
@@ -152,7 +150,6 @@ void ruleTests() {
     avoid_web_libraries_in_flutter.main();
     close_sinks.main();
     always_require_non_null_named_parameters.main();
-    prefer_const_constructors_in_immutables.main();
     public_member_api_docs.main();
     sort_pub_dependencies.main();
     use_build_context_synchronously.main();

test/integration_test.dart

@@ -20,6 +20,30 @@ class PreferConstConstructorsInImmutablesTest extends LintRuleTest {
   @override
   bool get addMetaPackageDep => true;
 
+  test_assertInitializer_canBeConst() async {
+    await assertDiagnostics(r'''
+import 'package:meta/meta.dart';
+
+@immutable
+class C {
+  C.named(a) : assert(a != null);
+}
+''', [
+      lint(57, 1),
+    ]);
+  }
+
+  test_assertInitializer_cannotBeConst() async {
+    await assertNoDiagnostics(r'''
+import 'package:meta/meta.dart';
+
+@immutable
+class C {
+  C.named(a) : assert(a.toString() == 'string');
+}
+''');
+  }
+
   test_returnOfInvalidType() async {
     await assertDiagnostics(r'''
 import 'package:meta/meta.dart';