[element model] fix unnecessary_null_checks

Bug: https://github.com/dart-lang/linter/issues/5099
Change-Id: I182fffbf5ba44b8e89e81aff64042c56828d6c3c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/390806
Reviewed-by: Brian Wilkerson <[email protected]>
Auto-Submit: Phil Quitslund <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: pq

pkg/linter/analyzer_use_new_elements.txt

@@ -28,6 +28,7 @@ lib/src/rules/avoid_js_rounded_ints.dart
 lib/src/rules/avoid_multiple_declarations_per_line.dart
 lib/src/rules/avoid_print.dart
 lib/src/rules/avoid_private_typedef_functions.dart
+lib/src/rules/avoid_redundant_argument_values.dart
 lib/src/rules/avoid_relative_lib_imports.dart
 lib/src/rules/avoid_return_types_on_setters.dart
 lib/src/rules/avoid_returning_null.dart
@@ -169,6 +170,7 @@ lib/src/rules/unnecessary_library_directive.dart
 lib/src/rules/unnecessary_library_name.dart
 lib/src/rules/unnecessary_new.dart
 lib/src/rules/unnecessary_null_aware_assignments.dart
+lib/src/rules/unnecessary_null_checks.dart
 lib/src/rules/unnecessary_null_in_if_null_operators.dart
 lib/src/rules/unnecessary_nullable_for_final_variable_declarations.dart
 lib/src/rules/unnecessary_parenthesis.dart

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

@@ -118,9 +118,9 @@ DartType? getExpectedType(PostfixExpression node) {
     } else if (grandParent is MethodInvocation) {
       var targetType = grandParent.realTarget?.staticType;
       if (targetType is InterfaceType) {
-        var targetClass = targetType.element;
+        var targetClass = targetType.element3;
 
-        if (targetClass.library.isDartAsync &&
+        if (targetClass.library2.isDartAsync &&
             targetClass.name == 'Completer' &&
             grandParent.methodName.name == 'complete') {
           return null;