fix

Author: josefpihrt

src/Refactorings/CSharp/Refactorings/CheckExpressionForNullRefactoring.cs

@@ -253,7 +253,17 @@ private static async Task<Document> RefactorAsync(
             }
         }
 
-        return await document.InsertNodeAfterAsync(statement, CreateNullCheck(expression), cancellationToken).ConfigureAwait(false);
+        SyntaxNode nodeInList = statement;
+        IfStatementSyntax nullCheck = CreateNullCheck(expression);
+        SyntaxNode newNode = nullCheck;
+
+        if (nodeInList.Parent is GlobalStatementSyntax globalStatement)
+        {
+            newNode = globalStatement.WithStatement(nullCheck);
+            nodeInList = globalStatement;
+        }
+
+        return await document.InsertNodeAfterAsync(nodeInList, newNode, cancellationToken).ConfigureAwait(false);
     }
 
     private static Task<Document> RefactorAsync(

src/Tests/Refactorings.Tests/RR0024CheckExpressionForNullTests.cs

@@ -0,0 +1,57 @@
+using System.Threading.Tasks;
+using Roslynator.Testing.CSharp;
+using Xunit;
+
+namespace Roslynator.CSharp.Refactorings.Tests;
+
+public class RR0024CheckExpressionForNullTests : AbstractCSharpRefactoringVerifier
+{
+    public override string RefactoringId { get; } = RefactoringIdentifiers.CheckExpressionForNull;
+
+    [Fact, Trait(Traits.Refactoring, RefactoringIdentifiers.CheckParameterForNull)]
+    public async Task Test()
+    {
+        await VerifyRefactoringAsync("""
+class C
+{
+    void M()
+    {
+        var [|x|] = "".ToString();
+    }
+}
+""", """
+class C
+{
+    void M()
+    {
+        var x = "".ToString();
+        if (x != null)
+        {
+
+        }
+    }
+}
+""", equivalenceKey: EquivalenceKey.Create(RefactoringId));
+    }
+
+    [Fact, Trait(Traits.Refactoring, RefactoringIdentifiers.CheckParameterForNull)]
+    public async Task Test_TopLevelStatement()
+    {
+        await VerifyRefactoringAsync("""
+
+var [|x|] = "".ToString();
+var y = x.ToString();
+
+""", """
+
+var x = "".ToString();
+
+if (x != null)
+{
+
+}
+var y = x.ToString();
+
+""", equivalenceKey: EquivalenceKey.Create(RefactoringId));
+    }
+}