Ensure generated types come after top level statements (#79378)

Author: CyrusNajmabadi

src/EditorFeatures/CSharpTest/CodeActions/GenerateType/GenerateTypeTests.cs

@@ -5901,4 +5901,26 @@ internal class Test
                 public int B { get; set; }
             }
             """, index: 1);
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/49649")]
+    public Task TestInTopLevelProgram()
+        => TestInRegularAndScriptAsync(
+            """
+            var student = new [|Student|]("Youssef");
+            Console.WriteLine(student.Name);
+            """,
+            """
+            var student = new Student("Youssef");
+            Console.WriteLine(student.Name);
+
+            internal class Student
+            {
+                private string v;
+
+                public Student(string v)
+                {
+                    this.v = v;
+                }
+            }
+            """, index: 1);
 }

src/EditorFeatures/CSharpTest/Diagnostics/AbstractCSharpDiagnosticProviderBasedUserDiagnosticTest.cs

@@ -2,23 +2,29 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-#nullable disable
+#if CODE_STYLE
+extern alias CODESTYLE_UTILITIES;
+#endif
 
 using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.CodeActions;
 using Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions;
 using Microsoft.CodeAnalysis.Editor.UnitTests.Diagnostics;
+using Microsoft.CodeAnalysis.Remote.Testing;
 using Xunit.Abstractions;
 
 namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.Diagnostics;
 
-public abstract partial class AbstractCSharpDiagnosticProviderBasedUserDiagnosticTest : AbstractDiagnosticProviderBasedUserDiagnosticTest
-{
-    protected AbstractCSharpDiagnosticProviderBasedUserDiagnosticTest(ITestOutputHelper logger)
-       : base(logger)
-    {
-    }
+#if CODE_STYLE
+using OptionsCollectionAlias = CODESTYLE_UTILITIES::Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions.OptionsCollection;
+#else
+using OptionsCollectionAlias = OptionsCollection;
+#endif
 
+public abstract partial class AbstractCSharpDiagnosticProviderBasedUserDiagnosticTest(ITestOutputHelper? logger)
+    : AbstractDiagnosticProviderBasedUserDiagnosticTest(logger)
+{
     protected override ParseOptions GetScriptOptions() => Options.Script;
 
     protected internal override string GetLanguage() => LanguageNames.CSharp;
@@ -158,8 +164,24 @@ public interface IAsyncEnumerator<out T> : IAsyncDisposable
         [StringSyntax(PredefinedEmbeddedLanguageNames.CSharpTest)] string initialMarkup,
         [StringSyntax(PredefinedEmbeddedLanguageNames.CSharpTest)] string expectedMarkup,
         int index = 0,
-        TestParameters parameters = null)
+        TestParameters? parameters = null)
     {
         return base.TestInRegularAndScript1Async(initialMarkup, expectedMarkup, index, parameters);
     }
+
+    internal new Task TestInRegularAndScriptAsync(
+        [StringSyntax(PredefinedEmbeddedLanguageNames.CSharpTest)] string initialMarkup,
+        [StringSyntax(PredefinedEmbeddedLanguageNames.CSharpTest)] string expectedMarkup,
+        int index = 0,
+        CodeActionPriority? priority = null,
+        CompilationOptions? compilationOptions = null,
+        OptionsCollectionAlias? options = null,
+        object? fixProviderData = null,
+        ParseOptions? parseOptions = null,
+        string? title = null,
+        TestHost testHost = TestHost.OutOfProcess)
+    {
+        return base.TestInRegularAndScriptAsync(
+            initialMarkup, expectedMarkup, index, priority, compilationOptions, options, fixProviderData, parseOptions, title, testHost);
+    }
 }

src/Features/Core/Portable/GenerateType/AbstractGenerateTypeService.cs

@@ -13,6 +13,7 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CodeActions;
 using Microsoft.CodeAnalysis.CodeGeneration;
+using Microsoft.CodeAnalysis.Collections;
 using Microsoft.CodeAnalysis.Internal.Log;
 using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.PooledObjects;
@@ -100,7 +101,7 @@ private ImmutableArray<CodeAction> GetActions(
         State state,
         CancellationToken cancellationToken)
     {
-        using var _ = ArrayBuilder<CodeAction>.GetInstance(out var result);
+        using var result = TemporaryArray<CodeAction>.Empty;
 
         var generateNewTypeInDialog = false;
         if (state.NamespaceToGenerateInOpt != null)

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/CodeGeneration/CSharpCodeGenerationHelpers.cs

@@ -172,14 +172,15 @@ public static SyntaxList<TDeclaration> Insert<TDeclaration>(
         CSharpCodeGenerationContextInfo info,
         IList<bool>? availableIndices,
         Func<SyntaxList<TDeclaration>, TDeclaration?>? after = null,
-        Func<SyntaxList<TDeclaration>, TDeclaration?>? before = null)
+        Func<SyntaxList<TDeclaration>, TDeclaration?>? before = null,
+        Func<SyntaxList<TDeclaration>, int, bool>? canPlaceAtIndex = null)
         where TDeclaration : SyntaxNode
     {
         var index = GetInsertionIndex(
             declarationList, declaration, info, availableIndices,
             CSharpDeclarationComparer.WithoutNamesInstance,
             CSharpDeclarationComparer.WithNamesInstance,
-            after, before);
+            after, before, canPlaceAtIndex);
 
         availableIndices?.Insert(index, true);
 

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/CSharp/CodeGeneration/NamedTypeGenerator.cs

@@ -59,7 +59,11 @@ public static CompilationUnitSyntax AddNamedTypeTo(
         CancellationToken cancellationToken)
     {
         var declaration = GenerateNamedTypeDeclaration(service, namedType, CodeGenerationDestination.CompilationUnit, info, cancellationToken);
-        var members = Insert(destination.Members, declaration, info, availableIndices);
+        var members = Insert(
+            destination.Members, declaration, info, availableIndices,
+            // We're adding a named type to a compilation unit.  If there are any global statements, we must place it after them.
+            after: static members => members.LastOrDefault(m => m is GlobalStatementSyntax),
+            canPlaceAtIndex: static (members, index) => index >= members.Count || members[index] is not GlobalStatementSyntax);
         return destination.WithMembers(members);
     }
 

src/Workspaces/SharedUtilitiesAndExtensions/Workspace/Core/CodeGeneration/CodeGenerationHelpers.cs

@@ -193,11 +193,14 @@ public static int GetInsertionIndex<TDeclaration>(
         IComparer<TDeclaration> comparerWithoutNameCheck,
         IComparer<TDeclaration> comparerWithNameCheck,
         Func<SyntaxList<TDeclaration>, TDeclaration?>? after = null,
-        Func<SyntaxList<TDeclaration>, TDeclaration?>? before = null)
+        Func<SyntaxList<TDeclaration>, TDeclaration?>? before = null,
+        Func<SyntaxList<TDeclaration>, int, bool>? canPlaceAtIndex = null)
         where TDeclaration : SyntaxNode
     {
         Contract.ThrowIfTrue(availableIndices != null && availableIndices.Count != declarationList.Count + 1);
 
+        canPlaceAtIndex ??= static (_, _) => true;
+
         // Try to strictly obey the after option by inserting immediately after the member containing the location
         if (info.Context.AfterThisLocation?.SourceTree is { } afterSourceTree &&
             afterSourceTree.FilePath == declarationList.FirstOrDefault()?.SyntaxTree.FilePath)
@@ -207,10 +210,8 @@ public static int GetInsertionIndex<TDeclaration>(
             {
                 var index = declarationList.IndexOf(afterMember);
                 index = GetPreferredIndex(index + 1, availableIndices, forward: true);
-                if (index != -1)
-                {
+                if (index != -1 && canPlaceAtIndex(declarationList, index))
                     return index;
-                }
             }
         }