Merge pull request #14868 from rchande/sighelpLinkedFiles

Fix sighelp crash in linked files

src/EditorFeatures/CSharpTest/SignatureHelp/TupleConstructionSignatureHelpProviderTests.cs

@@ -200,5 +200,35 @@ static void Main(string[] args)
 
             await TestAsync(markup, expectedOrderedItems, usePreviousCharAsTrigger: true);
         }
+
+        [WorkItem(14793, "https://github.com/dotnet/roslyn/issues/14793")]
+        [Fact, Trait(Traits.Feature, Traits.Features.SignatureHelp)]
+        public async Task DoNotCrashInLinkedFile()
+        {
+            var markup = @"<Workspace>
+    <Project Language=""C#"" CommonReferences=""true"" AssemblyName=""Proj1"" PreprocessorSymbols=""FOO"">
+        <Document FilePath=""SourceDocument""><![CDATA[
+class C
+{
+#if FOO
+    void bar()
+    {
+    }
+#endif
+    void foo()
+    {
+        (int, string) x = ($$
+    }
+}
+]]>
+        </Document>
+    </Project>
+    <Project Language=""C#"" CommonReferences=""true"" AssemblyName=""Proj2"">
+        <Document IsLinkFile=""true"" LinkAssemblyName=""Proj1"" LinkFilePath=""SourceDocument""/>
+    </Project>
+</Workspace>";
+            var expectedDescription = new SignatureHelpTestItem($"(int, string)", currentParameterIndex: 0);
+            await VerifyItemWithReferenceWorkerAsync(markup, new[] { expectedDescription }, false);
+        }
     }
 }

src/Features/CSharp/Portable/SignatureHelp/TupleConstructionSignatureHelpProvider.cs

@@ -152,21 +152,30 @@ protected override async Task<SignatureHelpItems> GetItemsWorkerAsync(Document d
         private SignatureHelpItems CreateItems(int position, SyntaxNode root, ISyntaxFactsService syntaxFacts, 
             SyntaxNode targetExpression, SemanticModel semanticModel, IEnumerable<INamedTypeSymbol> tupleTypes, CancellationToken cancellationToken)
         {
-            var prefixParts = SpecializedCollections.SingletonEnumerable(new SymbolDisplayPart(SymbolDisplayPartKind.Punctuation, null, "("));
-            var suffixParts = SpecializedCollections.SingletonEnumerable(new SymbolDisplayPart(SymbolDisplayPartKind.Punctuation, null, ")"));
-            var separatorParts = GetSeparatorParts();
+            var prefixParts = SpecializedCollections.SingletonEnumerable(new SymbolDisplayPart(SymbolDisplayPartKind.Punctuation, null, "(")).ToTaggedText();
+            var suffixParts = SpecializedCollections.SingletonEnumerable(new SymbolDisplayPart(SymbolDisplayPartKind.Punctuation, null, ")")).ToTaggedText();
+            var separatorParts = GetSeparatorParts().ToTaggedText();
 
-            var items = tupleTypes.Select(t =>
-                new SignatureHelpItem(isVariadic: false,
+            var items = tupleTypes.Select(tupleType => Convert(
+                tupleType, prefixParts, suffixParts, separatorParts, semanticModel, position))
+                .ToList();
+
+            var state = GetCurrentArgumentState(root, position, syntaxFacts, targetExpression.FullSpan, cancellationToken);
+            return CreateSignatureHelpItems(items, targetExpression.Span, state);
+        }
+
+        SignatureHelpItem Convert(INamedTypeSymbol tupleType, ImmutableArray<TaggedText> prefixParts, ImmutableArray<TaggedText> suffixParts,
+            ImmutableArray<TaggedText> separatorParts, SemanticModel semanticModel, int position)
+        {
+            return new SymbolKeySignatureHelpItem(
+                    symbol: tupleType,
+                    isVariadic: false,
                     documentationFactory: null,
                     prefixParts: prefixParts,
                     separatorParts: separatorParts,
                     suffixParts: suffixParts,
-                    parameters: ConvertTupleMembers(t, semanticModel, position),
-                    descriptionParts: null)).ToList();
-
-            var state = GetCurrentArgumentState(root, position, syntaxFacts, targetExpression.FullSpan, cancellationToken);
-            return CreateSignatureHelpItems(items, targetExpression.Span, state);
+                    parameters: ConvertTupleMembers(tupleType, semanticModel, position),
+                    descriptionParts: null);
         }
 
         private IEnumerable<SignatureHelpParameter> ConvertTupleMembers(INamedTypeSymbol tupleType, SemanticModel semanticModel, int position)

src/Features/Core/Portable/SignatureHelp/AbstractSignatureHelpProvider.cs

@@ -188,7 +188,7 @@ where part.Symbol.IsNormalAnonymousType()
             var finalItems = new List<SignatureHelpItem>();
             foreach (var item in itemsForCurrentDocument.Items)
             {
-                var symbolKey = ((SymbolKeySignatureHelpItem)item).SymbolKey;
+                var symbolKey = (item as SymbolKeySignatureHelpItem)?.SymbolKey;
                 if (symbolKey == null)
                 {
                     finalItems.Add(item);
@@ -224,7 +224,7 @@ where part.Symbol.IsNormalAnonymousType()
             foreach (var related in relatedDocuments)
             {
                 // If we don't have symbol keys, give up.
-                if (related.Item2.Any(s => ((SymbolKeySignatureHelpItem)s).SymbolKey == null))
+                if (related.Item2.Any(s => (s as SymbolKeySignatureHelpItem)?.SymbolKey == null))
                 {
                     continue;
                 }