Do not report inference failure on untyped parameters of overridding methods

While in the area, refactored _hasNonVirtualAnnotation calls to reduce null checks.

Change-Id: I74e3108e4cf1221cc1025d1283aacc1976757c09
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/203296
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

Author: srawlins

pkg/analyzer/lib/src/error/best_practices_verifier.dart

@@ -440,11 +440,12 @@ class BestPracticesVerifier extends RecursiveAstVisitor<void> {
         }
 
         final overriddenElement = getOverriddenPropertyAccessor();
-        if (_hasNonVirtualAnnotation(overriddenElement)) {
+        if (overriddenElement != null &&
+            _hasNonVirtualAnnotation(overriddenElement)) {
           _errorReporter.reportErrorForNode(
               HintCode.INVALID_OVERRIDE_OF_NON_VIRTUAL_MEMBER,
               field.name,
-              [field.name, overriddenElement!.enclosingElement.name]);
+              [field.name, overriddenElement.enclosingElement.name]);
         }
         if (!_invalidAccessVerifier._inTestDirectory) {
           _checkForAssignmentOfDoNotStore(field.initializer);
@@ -584,10 +585,6 @@ class BestPracticesVerifier extends RecursiveAstVisitor<void> {
 
     Name name = Name(_currentLibrary.source.uri, element.name);
 
-    bool elementIsOverride() =>
-        element is ClassMemberElement && enclosingElement is ClassElement
-            ? _inheritanceManager.getOverridden2(enclosingElement, name) != null
-            : false;
     ExecutableElement? getConcreteOverriddenElement() =>
         element is ClassMemberElement && enclosingElement is ClassElement
             ? _inheritanceManager.getMember2(enclosingElement, name,
@@ -610,21 +607,29 @@ class BestPracticesVerifier extends RecursiveAstVisitor<void> {
       _mustCallSuperVerifier.checkMethodDeclaration(node);
       _checkForUnnecessaryNoSuchMethod(node);
 
-      if (!node.isSetter && !elementIsOverride()) {
+      var elementIsOverride = element is ClassMemberElement &&
+              enclosingElement is ClassElement
+          ? _inheritanceManager.getOverridden2(enclosingElement, name) != null
+          : false;
+
+      if (!node.isSetter && !elementIsOverride) {
         _checkStrictInferenceReturnType(node.returnType, node, node.name.name);
       }
-      _checkStrictInferenceInParameters(node.parameters, body: node.body);
+      if (!elementIsOverride) {
+        _checkStrictInferenceInParameters(node.parameters, body: node.body);
+      }
 
       var overriddenElement = getConcreteOverriddenElement();
       if (overriddenElement == null && (node.isSetter || node.isGetter)) {
         overriddenElement = getOverriddenPropertyAccessor();
       }
 
-      if (_hasNonVirtualAnnotation(overriddenElement)) {
+      if (overriddenElement != null &&
+          _hasNonVirtualAnnotation(overriddenElement)) {
         _errorReporter.reportErrorForNode(
             HintCode.INVALID_OVERRIDE_OF_NON_VIRTUAL_MEMBER,
             node.name,
-            [node.name, overriddenElement!.enclosingElement.name]);
+            [node.name, overriddenElement.enclosingElement.name]);
       }
 
       super.visitMethodDeclaration(node);
@@ -1739,10 +1744,7 @@ class BestPracticesVerifier extends RecursiveAstVisitor<void> {
     return identifier?.name ?? '';
   }
 
-  static bool _hasNonVirtualAnnotation(ExecutableElement? element) {
-    if (element == null) {
-      return false;
-    }
+  static bool _hasNonVirtualAnnotation(ExecutableElement element) {
     if (element is PropertyAccessorElement && element.isSynthetic) {
       return element.variable.hasNonVirtual;
     }

pkg/analyzer/test/src/diagnostics/inference_failure_on_untyped_parameter_test.dart

@@ -208,22 +208,20 @@ class C {
   }
 
   test_parameter_inOverridingMethod() async {
-    await assertErrorsInCode(r'''
+    await assertNoErrorsInCode(r'''
 class C {
   void fn(int a) => print(a);
 }
 
 class D extends C {
   @override
-  void fn(var a) => print(a);
+  void fn(a) => print(a);
 }
-''', [
-      error(HintCode.INFERENCE_FAILURE_ON_UNTYPED_PARAMETER, 85, 5),
-    ]);
+''');
   }
 
   test_parameter_inOverridingMethod_withDefault() async {
-    await assertErrorsInCode(r'''
+    await assertNoErrorsInCode(r'''
 class C {
   void fn([int a = 7]) => print(a);
 }
@@ -232,9 +230,7 @@ class D extends C {
   @override
   void fn([var a = 7]) => print(a);
 }
-''', [
-      error(HintCode.INFERENCE_FAILURE_ON_UNTYPED_PARAMETER, 92, 5),
-    ]);
+''');
   }
 
   test_parameter_inOverridingMethod_withDefaultAndType() async {
@@ -263,6 +259,19 @@ class D extends C {
 ''');
   }
 
+  test_parameter_inOverridingMethod_withVar() async {
+    await assertNoErrorsInCode(r'''
+class C {
+  void fn(int a) => print(a);
+}
+
+class D extends C {
+  @override
+  void fn(var a) => print(a);
+}
+''');
+  }
+
   test_parameter_inTypedef_withoutType() async {
     await assertErrorsInCode(r'''
 typedef void cb(a);