Refactored avoid_unnecessary_type_assertions (#144)

* Refactored avoid_unnecessary_type_assertions

* - Updated changelog

Author: aderhachev

CHANGELOG.md

@@ -5,7 +5,8 @@
 - Fixed `avoid_unused_parameters` to report positional parameters from typedef if their name are not underscores.
 - Improvement for `avoid_returning_widget` lint:
   - ignores methods that override ones that return widget (build() for example)
-  - no longer allows returning widgets from methods/functions named build 
+  - no longer allows returning widgets from methods/functions named build
+- Fixed unexpected avoid_unnecessary_type_assertions
 
 ## 0.1.4
 
@@ -90,12 +91,12 @@
 - Update `dart_code_metrics` dependency to 5.7.3
 - Rename deprecated `member-ordering-extended` to `member-ordering`
 - Add rule for widgets methods order configuration:
-    - initState
-    - build
-    - didChangeDependencies
-    - didUpdateWidget
-    - deactivate
-    - dispose
+  - initState
+  - build
+  - didChangeDependencies
+  - didUpdateWidget
+  - deactivate
+  - dispose
 
 ## 0.0.15
 

lib/src/lints/avoid_unnecessary_type_assertions/avoid_unnecessary_type_assertions_rule.dart

@@ -98,23 +98,12 @@ class AvoidUnnecessaryTypeAssertions extends SolidLintRule {
     if (objectType == null || castedType == null) {
       return false;
     }
-
     final typeCast = TypeCast(
       source: objectType,
       target: castedType,
-      isReversed: true,
+      isReversed: node.notOperator != null,
     );
-
-    if (node.notOperator != null &&
-        objectType is! TypeParameterType &&
-        objectType is! DynamicType &&
-        !objectType.isDartCoreObject &&
-        typeCast.isUnnecessaryTypeCheck) {
-      return true;
-    } else {
-      final typeCast = TypeCast(source: objectType, target: castedType);
-      return typeCast.isUnnecessaryTypeCheck;
-    }
+    return typeCast.isUnnecessaryTypeCheck;
   }
 
   bool _isUnnecessaryWhereType(MethodInvocation node) {

lib/src/utils/typecast_utils.dart

@@ -28,26 +28,30 @@ class TypeCast {
     this.isReversed = false,
   });
 
-  /// Returns the first type from source's supertypes
-  /// which is corresponding to target or null
-  DartType? castTypeInHierarchy() {
+  /// Checks that type checking is unnecessary
+  bool get isUnnecessaryTypeCheck {
+    final source = this.source;
+
+    if (_isNullableCompatibility) {
+      return false;
+    }
+
     if (source.element == target.element) {
-      return source;
+      return _areGenericsWithSameTypeArgs;
     }
 
-    final objectType = source;
-    if (objectType is InterfaceType) {
-      return objectType.allSupertypes.firstWhereOrNull(
-        (value) => value.element == target.element,
+    if (source is InterfaceType) {
+      return source.allSupertypes.any(
+        (e) => e.element == target.element,
       );
     }
 
-    return null;
+    return false;
   }
 
   /// Checks for nullable type casts
   /// Only one case `Type? is Type` always valid assertion case.
-  bool get isNullableCompatibility {
+  bool get _isNullableCompatibility {
     final isObjectTypeNullable =
         source.nullabilitySuffix != NullabilitySuffix.none;
     final isCastedTypeNullable =
@@ -56,33 +60,8 @@ class TypeCast {
     return isObjectTypeNullable && !isCastedTypeNullable;
   }
 
-  /// Checks that type checking is unnecessary
-  /// [source] is the source expression type
-  /// [target] is the type against which the expression type is compared
-  /// and false for positive comparison, i.e. 'is', 'as' or 'whereType'
-  bool get isUnnecessaryTypeCheck {
-    if (isNullableCompatibility) {
-      return false;
-    }
-
-    final objectCastedType = castTypeInHierarchy();
-    if (objectCastedType == null) {
-      return isReversed;
-    }
-
-    final objectTypeCast = TypeCast(
-      source: objectCastedType,
-      target: target,
-    );
-    if (!objectTypeCast.areGenericsWithSameTypeArgs) {
-      return false;
-    }
-
-    return !isReversed;
-  }
-
   /// Checks for type arguments and compares them
-  bool get areGenericsWithSameTypeArgs {
+  bool get _areGenericsWithSameTypeArgs {
     if (source is DynamicType || target is DynamicType) {
       return false;
     }

lint_test/avoid_unnecessary_type_assertions_test.dart

@@ -1,4 +1,4 @@
-// ignore_for_file: prefer_const_declarations
+// ignore_for_file: prefer_const_declarations, prefer_match_file_name, cyclomatic_complexity, unused_element
 // ignore_for_file: unnecessary_nullable_for_final_variable_declarations
 // ignore_for_file: unnecessary_type_check
 // ignore_for_file: unused_local_variable
@@ -34,3 +34,14 @@ void fun() {
   // casting `Type? is Type` is allowed
   final castedD = nullableD is double;
 }
+
+class _A {}
+
+class _B extends _A {}
+
+class _C extends _A {}
+
+void noLint() {
+  final _A a = _B();
+  if (a is! _C) return;
+}