From d10df884adf65801757bb7179baa39befbaa529e Mon Sep 17 00:00:00 2001
From: Sam Harwell <Sam.Harwell@microsoft.com>
Date: Mon, 29 Mar 2021 18:48:09 -0700
Subject: [PATCH] Fix caret affinity in GetReferencedSymbolsToLeftOfCaretAsync

---
 .../AbstractSnippetExpansionClient.cs         |  8 +++++-
 .../CSharp/CSharpArgumentProvider.cs          | 28 +++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/src/VisualStudio/Core/Def/Implementation/Snippets/AbstractSnippetExpansionClient.cs b/src/VisualStudio/Core/Def/Implementation/Snippets/AbstractSnippetExpansionClient.cs
index f1243358170a..cfdedb05443b 100644
--- a/src/VisualStudio/Core/Def/Implementation/Snippets/AbstractSnippetExpansionClient.cs
+++ b/src/VisualStudio/Core/Def/Implementation/Snippets/AbstractSnippetExpansionClient.cs
@@ -722,7 +722,13 @@ private static async Task<ImmutableArray<ISymbol>> GetReferencedSymbolsToLeftOfC
             CancellationToken cancellationToken)
         {
             var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
-            var token = await semanticModel.SyntaxTree.GetTouchingTokenAsync(caretPosition.Position, cancellationToken).ConfigureAwait(false);
+
+            // GetTouchingTokenAsync prefers to return tokens to the right of the caret. Adjust the caret position one
+            // to the left to avoid this.
+            if (caretPosition.Position == 0)
+                return ImmutableArray<ISymbol>.Empty;
+
+            var token = await semanticModel.SyntaxTree.GetTouchingTokenAsync(caretPosition.Position - 1, cancellationToken).ConfigureAwait(false);
             var semanticInfo = semanticModel.GetSemanticInfo(token, document.Project.Solution.Workspace, cancellationToken);
             return semanticInfo.ReferencedSymbols;
         }
diff --git a/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpArgumentProvider.cs b/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpArgumentProvider.cs
index 705cb6177076..ee83de3f8aae 100644
--- a/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpArgumentProvider.cs
+++ b/src/VisualStudio/IntegrationTest/IntegrationTests/CSharp/CSharpArgumentProvider.cs
@@ -57,6 +57,34 @@ public void Method()
             VisualStudio.Editor.Verify.CurrentLineText("f.ToString()$$", assertCaretPosition: true);
         }
 
+        [WpfFact]
+        public void TabTabBeforeSemicolon()
+        {
+            SetUpEditor(@"
+public class Test
+{
+    private object f;
+
+    public void Method()
+    {
+        $$;
+    }
+}
+");
+
+            VisualStudio.Editor.SendKeys("f.ToSt");
+
+            VisualStudio.Editor.SendKeys(VirtualKey.Tab);
+            VisualStudio.Editor.Verify.CurrentLineText("f.ToString$$;", assertCaretPosition: true);
+
+            VisualStudio.Editor.SendKeys(VirtualKey.Tab);
+            VisualStudio.Workspace.WaitForAllAsyncOperations(Helper.HangMitigatingTimeout, FeatureAttribute.SignatureHelp);
+            VisualStudio.Editor.Verify.CurrentLineText("f.ToString($$);", assertCaretPosition: true);
+
+            VisualStudio.Editor.SendKeys(VirtualKey.Tab);
+            VisualStudio.Editor.Verify.CurrentLineText("f.ToString()$$;", assertCaretPosition: true);
+        }
+
         [WpfFact]
         public void TabTabCompletionWithArguments()
         {