fix: support variables shadowing for avoid-unused-parameters (#993)

Author: incendial

CHANGELOG.md

@@ -3,8 +3,9 @@
 ## Unreleased
 
 * feat: support passing file paths to all commands.
-* fix: avoid-top-level-members-in-tests ignore lib.
+* fix: avoid-top-level-members-in-tests ignore lib
 * fix: `--reporter=json` for `check-unnecessary-nullable` crashes, saying `Converting object to an encodable object failed: Instance of 'MappedIterable<FormalParameter, String>'`.
+* fix: support variables shadowing for [`avoid-unused-parameters`](https://dartcodemetrics.dev/docs/rules/common/avoid-unused-parameters).
 * fix: support not named builder parameters for [`avoid-returning-widgets`](https://dartcodemetrics.dev/docs/rules/flutter/avoid-returning-widgets).
 * feat: make [`avoid-unnecessary-type-assertions`](https://dartcodemetrics.dev/docs/rules/common/avoid-unnecessary-type-assertions) handle is! checks.
 

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/avoid_unused_parameters_rule.dart

@@ -1,10 +1,9 @@
 // ignore_for_file: public_member_api_docs
 
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/syntactic_entity.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
-import 'package:collection/collection.dart';
+import 'package:analyzer/dart/element/element.dart';
 
 import '../../../../../utils/node_utils.dart';
 import '../../../lint_utils.dart';

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/visitor.dart

@@ -29,7 +29,7 @@ class _Visitor extends RecursiveAstVisitor<void> {
     if (!isOverride) {
       _unusedParameters.addAll(
         _getUnusedParameters(
-          node.body.childEntities,
+          node.body,
           parameters.parameters,
         ).where(_hasNoUnderscoresInName),
       );
@@ -49,81 +49,47 @@ class _Visitor extends RecursiveAstVisitor<void> {
 
     _unusedParameters.addAll(
       _getUnusedParameters(
-        node.functionExpression.body.childEntities,
+        node.functionExpression.body,
         parameters.parameters,
       ).where(_hasNoUnderscoresInName),
     );
   }
 
-  Iterable<FormalParameter> _getUnusedParameters(
-    Iterable<SyntacticEntity> children,
+  Set<FormalParameter> _getUnusedParameters(
+    AstNode body,
     Iterable<FormalParameter> parameters,
   ) {
-    final result = <FormalParameter>[];
+    final result = <FormalParameter>{};
+    final visitor = _IdentifiersVisitor();
+    body.visitChildren(visitor);
 
-    final names = parameters
-        .map((parameter) => parameter.identifier?.name)
-        .whereNotNull()
-        .toList();
-    final usedNames = _getUsedNames(children, names, []);
+    final allIdentifierElements = visitor.elements;
 
     for (final parameter in parameters) {
-      final name = parameter.identifier?.name;
-      if (name != null && !usedNames.contains(name)) {
+      final name = parameter.identifier;
+      if (name != null && !allIdentifierElements.contains(name.staticElement)) {
         result.add(parameter);
       }
     }
 
     return result;
   }
 
-  Iterable<String> _getUsedNames(
-    Iterable<SyntacticEntity> children,
-    List<String> parametersNames,
-    Iterable<String> ignoredNames,
-  ) {
-    final usedNames = <String>[];
-    final ignoredForSubtree = [...ignoredNames];
+  bool _hasNoUnderscoresInName(FormalParameter parameter) =>
+      parameter.identifier != null &&
+      parameter.identifier!.name.replaceAll('_', '').isNotEmpty;
+}
 
-    if (parametersNames.isEmpty) {
-      return usedNames;
-    }
+class _IdentifiersVisitor extends RecursiveAstVisitor<void> {
+  final elements = <Element>{};
 
-    for (final child in children) {
-      if (child is FunctionExpression) {
-        final parameters = child.parameters;
-        if (parameters != null) {
-          for (final parameter in parameters.parameters) {
-            final name = parameter.identifier?.name;
-            if (name != null) {
-              ignoredForSubtree.add(name);
-            }
-          }
-        }
-      } else if (child is Identifier &&
-          parametersNames.contains(child.name) &&
-          !ignoredForSubtree.contains(child.name) &&
-          !(child.parent is PropertyAccess &&
-              (child.parent as PropertyAccess).target != child)) {
-        final name = child.name;
-
-        parametersNames.remove(name);
-        usedNames.add(name);
-      }
+  @override
+  void visitSimpleIdentifier(SimpleIdentifier node) {
+    super.visitSimpleIdentifier(node);
 
-      if (child is AstNode) {
-        usedNames.addAll(_getUsedNames(
-          child.childEntities,
-          parametersNames,
-          ignoredForSubtree,
-        ));
-      }
+    final element = node.staticElement;
+    if (element != null) {
+      elements.add(element);
     }
-
-    return usedNames;
   }
-
-  bool _hasNoUnderscoresInName(FormalParameter parameter) =>
-      parameter.identifier != null &&
-      parameter.identifier!.name.replaceAll('_', '').isNotEmpty;
 }

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/avoid_unused_parameters_rule_test.dart

@@ -35,8 +35,8 @@ void main() {
 
       RuleTestHelper.verifyIssues(
         issues: issues,
-        startLines: [8, 11, 21, 24, 35, 29, 41, 47],
-        startColumns: [20, 40, 20, 20, 28, 38, 20, 23],
+        startLines: [8, 11, 21, 24, 35, 29, 41, 47, 53],
+        startColumns: [20, 40, 20, 20, 28, 38, 20, 23, 15],
         locationTexts: [
           'String string',
           'String secondString',
@@ -46,6 +46,7 @@ void main() {
           'String string',
           'TestClass object',
           'String string',
+          'String value',
         ],
         messages: [
           'Parameter is unused.',
@@ -56,6 +57,7 @@ void main() {
           'Parameter is unused.',
           'Parameter is unused.',
           'Parameter is unused.',
+          'Parameter is unused.',
         ],
       );
     });

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/examples/incorrect_example.dart

@@ -48,3 +48,10 @@ mixin AbstractMixin {
     return 'string';
   }
 }
+
+// LINT
+int shadowing(String value) {
+  final value = 1;
+
+  return value;
+}