From ef2de0a2d16eeb032c2d2f40e01d13de7a84b79a Mon Sep 17 00:00:00 2001
From: "Joshua \"Yoshi\" Askharoun" <jjask7@gmail.com>
Date: Mon, 24 Nov 2025 02:18:59 -0600
Subject: [PATCH] Prevent DIS from producing invalid statements

---
 libs/UIX.DecompXml/Decompiler.Script.cs       |  4 ++
 .../Extensions/SyntaxNodeExtensions.cs        | 64 +++++++++++++++++++
 test/NOWPLAYINGLAND_decomp.uix                | 14 ++--
 3 files changed, 74 insertions(+), 8 deletions(-)
 create mode 100644 libs/UIX.DecompXml/Extensions/SyntaxNodeExtensions.cs

diff --git a/libs/UIX.DecompXml/Decompiler.Script.cs b/libs/UIX.DecompXml/Decompiler.Script.cs
index 1ccb18b..bbd50a4 100644
--- a/libs/UIX.DecompXml/Decompiler.Script.cs
+++ b/libs/UIX.DecompXml/Decompiler.Script.cs
@@ -4,6 +4,7 @@ using Microsoft.CodeAnalysis.CSharp.Extensions;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.Iris.Asm.Models;
 using Microsoft.Iris.Debug.Symbols;
+using Microsoft.Iris.DecompXml.Extensions;
 using Microsoft.Iris.DecompXml.Mock;
 using Microsoft.Iris.Markup;
 using Microsoft.Iris.Markup.UIX;
@@ -127,6 +128,9 @@ partial class Decompiler
                                     break;
                             }
 
+                            if (!expr.IsStatementExpression())
+                                break;
+
                             cfa.AppendToBlock(ExpressionStatement(expr));
                         }
                         break;
diff --git a/libs/UIX.DecompXml/Extensions/SyntaxNodeExtensions.cs b/libs/UIX.DecompXml/Extensions/SyntaxNodeExtensions.cs
new file mode 100644
index 0000000..82cac4c
--- /dev/null
+++ b/libs/UIX.DecompXml/Extensions/SyntaxNodeExtensions.cs
@@ -0,0 +1,64 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+
+namespace Microsoft.Iris.DecompXml.Extensions;
+
+internal static class SyntaxNodeExtensions
+{
+    public static bool IsStatementExpression(this SyntaxNode syntax)
+    {
+        // The grammar gives:
+        //
+        // expression-statement:
+        //     statement-expression ;
+        //
+        // statement-expression:
+        //     invocation-expression
+        //     object-creation-expression
+        //     assignment
+        //     post-increment-expression
+        //     post-decrement-expression
+        //     pre-increment-expression
+        //     pre-decrement-expression
+        //     await-expression
+
+        switch (syntax.Kind())
+        {
+            case SyntaxKind.InvocationExpression:
+            case SyntaxKind.ObjectCreationExpression:
+            case SyntaxKind.SimpleAssignmentExpression:
+            case SyntaxKind.AddAssignmentExpression:
+            case SyntaxKind.SubtractAssignmentExpression:
+            case SyntaxKind.MultiplyAssignmentExpression:
+            case SyntaxKind.DivideAssignmentExpression:
+            case SyntaxKind.ModuloAssignmentExpression:
+            case SyntaxKind.AndAssignmentExpression:
+            case SyntaxKind.OrAssignmentExpression:
+            case SyntaxKind.ExclusiveOrAssignmentExpression:
+            case SyntaxKind.LeftShiftAssignmentExpression:
+            case SyntaxKind.RightShiftAssignmentExpression:
+            case SyntaxKind.UnsignedRightShiftAssignmentExpression:
+            case SyntaxKind.CoalesceAssignmentExpression:
+            case SyntaxKind.PostIncrementExpression:
+            case SyntaxKind.PostDecrementExpression:
+            case SyntaxKind.PreIncrementExpression:
+            case SyntaxKind.PreDecrementExpression:
+            case SyntaxKind.AwaitExpression:
+                return true;
+
+            case SyntaxKind.ConditionalAccessExpression:
+                var access = (ConditionalAccessExpressionSyntax)syntax;
+                return IsStatementExpression(access.WhenNotNull);
+
+            // Allow missing IdentifierNames; they will show up in error cases
+            // where there is no statement whatsoever.
+
+            case SyntaxKind.IdentifierName:
+                return syntax.IsMissing;
+
+            default:
+                return false;
+        }
+    }
+}
diff --git a/test/NOWPLAYINGLAND_decomp.uix b/test/NOWPLAYINGLAND_decomp.uix
index e43867f..2824041 100644
--- a/test/NOWPLAYINGLAND_decomp.uix
+++ b/test/NOWPLAYINGLAND_decomp.uix
@@ -272,7 +272,7 @@ ActionContainer.Visible = #SaveAsPlaylistButton.Visible # || #ShowMPContentCheck
 ]]></Script>
       <Script><![CDATA[
 [DeclareTrigger(CurrentlyPlayingTrackMixAvailability.Available)]
-object track = zuneUI:TransportControls.Instance.CurrentTrack;
+zuneUI:PlaybackTrack track = zuneUI:TransportControls.Instance.CurrentTrack;
 if ((Page.ShowMixOnEntry && track != null) && (Page.InitialPlaybackID == track.PlaybackID) && #CurrentlyPlayingTrackMixAvailability.Available #)
 {
     CurrentlyPlayingTrackMixAvailability.UpdateMixSeed.Invoke();
@@ -670,14 +670,12 @@ if (playingVideo)
     {
         object naturalWidth = stream.ContentHeight * stream.ContentAspectWidth / stream.ContentAspectHeight;
         object naturalHeight = stream.ContentHeight;
-        object wndWidth = #Window.ClientSize #.Width;
-        object wndHeight = Window.ClientSize.Height;
+        int wndWidth = #Window.ClientSize #.Width;
+        int wndHeight = Window.ClientSize.Height;
         if (wndWidth != 0 && wndHeight != 0)
         {
             object scaleX = (float)(wndWidth) / (float)(naturalWidth);
-            ((float)(wndWidth)) / ((float)(naturalWidth));
             object scaleY = (float)(wndHeight) / (float)(naturalHeight);
-            ((float)(wndHeight)) / ((float)(naturalHeight));
             int scale = system:Math.Min(scaleX, scaleY);
             maxVideoSizeX = #TransportControls.ZoomScaleFactor # * naturalWidth;
             maxVideoSizeY = TransportControls.ZoomScaleFactor * naturalHeight;
@@ -1320,7 +1318,7 @@ if (ListModel.SelectionManager != null && ListModel.SelectionManager.IsSelected(
     <Scripts>
       <Script><![CDATA[
 [DeclareTrigger(zuneUI:TransportControls.Instance.CurrentTrack)]
-object track = #zuneUI:TransportControls.Instance.CurrentTrack #;
+zuneUI:PlaybackTrack track = #zuneUI:TransportControls.Instance.CurrentTrack #;
 if (LibraryAlbumInfo != null)
 {
     Class.DisposeOwnedObject(LibraryAlbumInfo);
@@ -1513,7 +1511,7 @@ if (RotateInfo.Enabled)
 [DeclareTrigger(NowPlayingBackgroundHelper.Visible)]
 MPTrackQuery.Enabled = false;
 MPTrackQuery.Id = null;
-object currentTrack = zuneUI:TransportControls.Instance.CurrentTrack;
+zuneUI:PlaybackTrack currentTrack = zuneUI:TransportControls.Instance.CurrentTrack;
 if (#NowPlayingBackgroundHelper.Visible # && NowPlayingBackgroundHelper.Visible || !currentTrack.IsInVisibleCollection && util:FeatureEnablement.IsFeatureEnabled(zuneDBApi:Features.eMusic))
 {
     MPTrackQuery.Id = TrackId.ToString();
@@ -1530,7 +1528,7 @@ ArtistQuery.Enabled = false;
 ArtistQuery.Id = null;
 TopListenersQuery.Enabled = false;
 TopListenersQuery.ArtistId = null;
-object currentTrack = zuneUI:TransportControls.Instance.CurrentTrack;
+zuneUI:PlaybackTrack currentTrack = zuneUI:TransportControls.Instance.CurrentTrack;
 if (((!zuneUI:GuidHelper.IsEmpty(ArtistId) && #NowPlayingBackgroundHelper.Visible # && util:FeatureEnablement.IsFeatureEnabled(zuneDBApi:Features.eMusic) && configuration:ClientConfiguration.Playback.ShowNowPlayingClipAnimations) && (iris:Application.RenderingQuality == iris:RenderingQuality.MaxQuality)) && (currentTrack != null) && currentTrack.IsMusic)
 {
     ArtistPhotosQuery.Id = ArtistId.ToString();