[element model] migrate prefer_void_to_null

Bug: https://github.com/dart-lang/linter/issues/5099
Change-Id: Ib02a59132056c0e2856eee30ac6cdc1a6e50cd67
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/389200
Commit-Queue: Phil Quitslund <[email protected]>
Auto-Submit: Phil Quitslund <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: pq

pkg/analyzer/lib/src/dart/element/inheritance_manager3.dart

@@ -153,6 +153,9 @@ class InheritanceManager3 {
   @experimental
   ExecutableElement2? getInherited3(InterfaceType type, Name name) {
     var element = getInherited(type, name);
+    if (element is ExecutableMember) {
+      return element as ExecutableElement2;
+    }
     return (element as ExecutableFragment?)?.element;
   }
 

pkg/linter/lib/src/extensions.dart

@@ -521,6 +521,26 @@ extension InhertanceManager3Extension on InheritanceManager3 {
     var libraryUri = interfaceElement.library.source.uri;
     return getInherited(interfaceElement.thisType, Name(libraryUri, name));
   }
+
+  /// Returns the class member that is overridden by [member], if there is one,
+  /// as defined by [getInherited].
+  ExecutableElement2? overriddenMember2(Element2? member) {
+    if (member == null) {
+      return null;
+    }
+
+    var interfaceElement = member.thisOrAncestorOfType2<InterfaceElement2>();
+    if (interfaceElement == null) {
+      return null;
+    }
+    var name = member.name;
+    if (name == null) {
+      return null;
+    }
+
+    var libraryUri = interfaceElement.library2.firstFragment.source.uri;
+    return getInherited3(interfaceElement.thisType, Name(libraryUri, name));
+  }
 }
 
 extension InterfaceElementExtension on InterfaceElement {

pkg/linter/lib/src/rules/prefer_void_to_null.dart

@@ -46,8 +46,8 @@ class _Visitor extends SimpleAstVisitor<void> {
     // Make sure we're checking a return type.
     if (parent.returnType?.offset != node.offset) return false;
 
-    var member =
-        context.inheritanceManager.overriddenMember(parent.declaredElement);
+    var member = context.inheritanceManager
+        .overriddenMember2(parent.declaredFragment?.element);
     if (member == null) return false;
 
     var returnType = member.returnType;