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Konoshenko Vlad
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feat: add static code diagnostics avoid-unnecessary-type-assertions (#549)
* feat: add static code diagnostics `avoid-unnecessary-type-assertions` * feat: remove from overview * feat: formatted code * feat: formatted code * feat: remove as operator * Update CHANGELOG.md * Update CHANGELOG.md * doc: updated documentation * doc: updated documentation * doc: updated documentation * doc: updated documentation * doc: updated documentation * doc: updated documentation * doc: updated documentation
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‎CHANGELOG.md

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@@ -3,6 +3,7 @@
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## Unreleased
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* feat: introduce file metrics
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* feat: add static code diagnostics `avoid-unnecessary-type-assertions`
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* refactor: cleanup anti-patterns, metrics and rules documentation
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## 4.6.0

‎lib/src/analyzers/lint_analyzer/rules/rules_factory.dart

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@@ -7,6 +7,7 @@ import 'rules_list/avoid_non_null_assertion/avoid_non_null_assertion.dart';
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import 'rules_list/avoid_preserve_whitespace_false/avoid_preserve_whitespace_false.dart';
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import 'rules_list/avoid_returning_widgets/avoid_returning_widgets.dart';
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import 'rules_list/avoid_unnecessary_setstate/avoid_unnecessary_setstate.dart';
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import 'rules_list/avoid_unnecessary_type_assertions/avoid_unnecessary_type_assertions.dart';
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import 'rules_list/avoid_unused_parameters/avoid_unused_parameters.dart';
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import 'rules_list/avoid_wrapping_in_padding/avoid_wrapping_in_padding.dart';
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import 'rules_list/binary_expression_operand_order/binary_expression_operand_order.dart';
@@ -50,6 +51,8 @@ final _implementedRules = <String, Rule Function(Map<String, Object>)>{
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AvoidReturningWidgetsRule(config),
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AvoidUnnecessarySetStateRule.ruleId: (config) =>
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AvoidUnnecessarySetStateRule(config),
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AvoidUnnecessaryTypeAssertions.ruleId: (config) =>
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AvoidUnnecessaryTypeAssertions(config),
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AvoidUnusedParametersRule.ruleId: (config) =>
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AvoidUnusedParametersRule(config),
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AvoidWrappingInPaddingRule.ruleId: (config) =>

‎lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_unnecessary_type_assertions/avoid_unnecessary_type_assertions.dart

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import 'package:analyzer/dart/ast/ast.dart';
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import 'package:analyzer/dart/ast/visitor.dart';
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import 'package:analyzer/dart/element/type.dart';
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import '../../../../../utils/node_utils.dart';
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import '../../../lint_utils.dart';
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import '../../../models/internal_resolved_unit_result.dart';
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import '../../../models/issue.dart';
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import '../../../models/severity.dart';
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import '../../dart_rule_utils.dart';
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import '../../models/common_rule.dart';
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import '../../rule_utils.dart';
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part 'visitor.dart';
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class AvoidUnnecessaryTypeAssertions extends CommonRule {
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static const String ruleId = 'avoid-unnecessary-type-assertions';
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AvoidUnnecessaryTypeAssertions([Map<String, Object> config = const {}])
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: super(
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id: ruleId,
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severity: readSeverity(config, Severity.style),
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excludes: readExcludes(config),
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);
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@override
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Iterable<Issue> check(InternalResolvedUnitResult source) {
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final visitor = _Visitor();
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source.unit.visitChildren(visitor);
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return visitor.expressions.entries
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.map(
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(node) => createIssue(
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rule: this,
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location: nodeLocation(node: node.key, source: source),
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message: 'Avoid unnecessary "${node.value}" assertion.',
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),
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)
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.toList(growable: false);
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}
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}

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

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part of 'avoid_unnecessary_type_assertions.dart';
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class _Visitor extends RecursiveAstVisitor<void> {
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final _expressions = <Expression, String>{};
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Map<Expression, String> get expressions => _expressions;
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@override
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void visitMethodInvocation(MethodInvocation node) {
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super.visitMethodInvocation(node);
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const methodName = 'whereType';
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final isWhereTypeFunction = node.methodName.name == methodName;
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if (isIterableOrSubclass(node.realTarget?.staticType) &&
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isWhereTypeFunction &&
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node.target?.staticType is InterfaceType) {
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final interfaceType = node.target?.staticType as InterfaceType;
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final isTypeHasGeneric = interfaceType.typeArguments.isNotEmpty;
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final isCastedHasGeneric =
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node.typeArguments?.arguments.isNotEmpty ?? false;
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if (isTypeHasGeneric &&
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isCastedHasGeneric &&
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_isUselessTypeCheck(
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interfaceType.typeArguments.first,
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node.typeArguments?.arguments.first.type,
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)) {
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_expressions[node] = methodName;
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}
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}
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}
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@override
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void visitIsExpression(IsExpression node) {
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final objectType = node.expression.staticType;
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final castedType = node.type.type;
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if (_isUselessTypeCheck(objectType, castedType)) {
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_expressions[node] = 'is';
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}
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}
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bool _isUselessTypeCheck(
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DartType? objectType,
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DartType? castedType,
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) {
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if (objectType == null || castedType == null) {
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return false;
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}
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// Checked type name
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final typeName = objectType.getDisplayString(withNullability: true);
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// Casted type name with nullability
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final castedNameNull = castedType.getDisplayString(withNullability: true);
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// Casted type name without nullability
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final castedName = castedType.getDisplayString(withNullability: false);
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// Validation checks
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final isTypeSame = '$typeName?' == castedNameNull || typeName == castedName;
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final isTypeInheritor = _isInheritorType(objectType, castedNameNull);
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final isTypeWithGeneric = objectType is InterfaceType &&
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castedType is InterfaceType &&
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_isTypeWithGeneric(objectType, castedType);
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return isTypeSame || isTypeInheritor || isTypeWithGeneric;
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}
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bool _isTypeWithGeneric(InterfaceType objectType, InterfaceType castedType) {
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final objectTypeArguments = objectType.typeArguments;
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final castedTypeArguments = castedType.typeArguments;
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final isHasGeneric = objectTypeArguments.isNotEmpty;
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final isCount = objectTypeArguments.length == castedTypeArguments.length;
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if (isHasGeneric && isCount) {
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if (castedType.element.name == objectType.element.name) {
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for (var i = 0; i < objectTypeArguments.length; i++) {
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final isCheckUseless = _isUselessTypeCheck(
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objectTypeArguments[i],
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castedTypeArguments[i],
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);
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if (!isCheckUseless) {
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return false;
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}
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}
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return true;
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}
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}
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return false;
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}
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bool _isInheritorType(DartType objectType, String castedNameNull) =>
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objectType is InterfaceType &&
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objectType.allSupertypes
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.any((value) => _isInheritor(value, castedNameNull));
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bool _isInheritor(DartType? type, String typeName) =>
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type?.getDisplayString(withNullability: false) == typeName;
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}

‎test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unnecessary_type_assertions/avoid_unnecessary_type_assertions_test.dart

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import 'package:dart_code_metrics/src/analyzers/lint_analyzer/models/severity.dart';
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import 'package:dart_code_metrics/src/analyzers/lint_analyzer/rules/rules_list/avoid_unnecessary_type_assertions/avoid_unnecessary_type_assertions.dart';
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import 'package:test/test.dart';
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import '../../../../../helpers/rule_test_helper.dart';
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const _path = 'avoid_unnecessary_type_assertions/examples';
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const _classExampleWithIs = '$_path/example_with_is.dart';
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const _classExampleCases = '$_path/example_cases.dart';
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void main() {
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group('AvoidUnnecessaryTypeAssertions', () {
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test('initialization', () async {
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final unit = await RuleTestHelper.resolveFromFile(_classExampleWithIs);
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final issues = AvoidUnnecessaryTypeAssertions().check(unit);
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RuleTestHelper.verifyInitialization(
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issues: issues,
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ruleId: 'avoid-unnecessary-type-assertions',
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severity: Severity.style,
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);
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});
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test('reports about found all issues in example_with_is.dart', () async {
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final unit = await RuleTestHelper.resolveFromFile(_classExampleWithIs);
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final issues = AvoidUnnecessaryTypeAssertions().check(unit);
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RuleTestHelper.verifyIssues(
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issues: issues,
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startOffsets: [
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120,
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228,
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539,
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584,
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630,
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672,
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718,
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1020,
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1053,
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],
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startLines: [
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6,
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8,
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21,
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22,
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23,
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25,
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38,
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],
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startColumns: [
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20,
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21,
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20,
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20,
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20,
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20,
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20,
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5,
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],
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endOffsets: [
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143,
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252,
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555,
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601,
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643,
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689,
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731,
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],
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locationTexts: [
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'regularString is String',
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'regularString is String?',
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'animal is Animal',
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'cat is HomeAnimal',
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'cat is Animal',
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'dog is HomeAnimal',
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'dog is Animal',
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'myList is List<int>',
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'myList.whereType<int>()',
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],
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messages: [
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "whereType" assertion.',
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],
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);
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});
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test('reports about found all issues in example_cases.dart', () async {
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final unit = await RuleTestHelper.resolveFromFile(_classExampleCases);
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final issues = AvoidUnnecessaryTypeAssertions().check(unit);
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RuleTestHelper.verifyIssues(
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issues: issues,
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startOffsets: [121, 235, 279, 454, 486, 514, 566],
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startLines: [10, 16, 19, 26, 27, 28, 29],
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startColumns: [14, 14, 5, 5, 5, 5, 21],
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endOffsets: [127, 253, 310, 473, 508, 537, 578],
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locationTexts: [
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'b is A',
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'regular is String?',
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"['1', '2'].whereType<String?>()",
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'myList is List<int>',
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'myList is List<Object>',
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'myList.whereType<int>()',
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'a is dynamic',
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],
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messages: [
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "whereType" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "is" assertion.',
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'Avoid unnecessary "whereType" assertion.',
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'Avoid unnecessary "is" assertion.',
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],
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);
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});
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});
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}

‎test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unnecessary_type_assertions/examples/example_cases.dart

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class A {}
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class B extends A {}
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class Example4 {
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final a = A();
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final b = B();
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final res = a is B;
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final re = b is A; // LINT
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final String? nullable;
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final String regular;
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final s1 = nullable is String;
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final s2 = regular is String?; // LINT
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main() {
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['1', '2'].whereType<String?>(); // LINT
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dynamic a;
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final list = <dynamic>[1, 'as', 1];
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a is String;
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list.whereType<String>();
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final myList = [1, 2];
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myList is List<int>; //LINT
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myList is List<Object>;
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myList.whereType<int>(); //LINT
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final result2 = a is dynamic;
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list.whereType();
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}
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}

‎test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unnecessary_type_assertions/examples/example_with_is.dart

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class Example1 {
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final regularString = '';
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final String? nullableString = null;
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void main() {
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final result = regularString is String; // LINT
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final result2 = nullableString is String?; // LINT
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final result3 = regularString is String?; // LINT
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final result4 = nullableString is String;
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}
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}
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class Example2 {
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final Animal animal = Animal();
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final HomeAnimal homeAnimal = HomeAnimal();
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final Cat cat = Cat();
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final Dog dog = Dog();
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void main() {
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final result = animal is HomeAnimal;
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final result = animal is Animal; // LINT
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final result = cat is HomeAnimal; // LINT
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final result = cat is Animal; // LINT
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final result = dog is HomeAnimal; // LINT
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final result = dog is Animal; // LINT
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final result = animal is Dog;
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final result = animal is Cat;
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final result = homeAnimal is Cat;
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final result = homeAnimal is Dog;
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final result = homeAnimal is dynamic;
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}
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}
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class Example3 {
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final myList = <int>[1, 2, 3];
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void main() {
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final result = myList is List<int>; // LINT
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myList.whereType<int>();
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myList.whereType<double>(); // LINT
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}
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}
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class Animal {}
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class HomeAnimal extends Animal {}
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class Dog extends HomeAnimal {}
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class Cat extends HomeAnimal {}

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