Do not report SA1141 for single-element tuples

Fixes #3055

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp7/ReadabilityRules/SA1141CSharp7UnitTests.cs

@@ -218,6 +218,26 @@ public void TestMethod(object x)
             await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
         }
 
+        [Fact]
+        [WorkItem(3055, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3055")]
+        public async Task ValidateSingleElementValueTupleUsageAsync()
+        {
+            var testCode = @"using System;
+
+public class TestClass
+{
+    public void TestMethod()
+    {
+        var test1 = default(ValueTuple<int>);
+        var test2 = default(ValueTuple<ValueTuple<int>>);
+        ValueTuple<int> test3 = ValueTuple.Create(3);
+    }
+}
+";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
+
         /// <summary>
         /// Validates that the usage of <see cref="System.ValueTuple"/> within exception filtering will produce no diagnostics.
         /// </summary>

StyleCop.Analyzers/StyleCop.Analyzers/ReadabilityRules/SA1141UseTupleSyntax.cs

@@ -121,6 +121,12 @@ private static void HandleInvocationExpression(SyntaxNodeAnalysisContext context
             }
 
             var invocationExpression = (InvocationExpressionSyntax)context.Node;
+            if (invocationExpression.ArgumentList.Arguments.Count < 2)
+            {
+                // Tuple creation with less than two elements cannot use the language syntax
+                return;
+            }
+
             if (!invocationExpression.Expression.IsKind(SyntaxKind.SimpleMemberAccessExpression))
             {
                 return;
@@ -209,7 +215,7 @@ private static void CheckTupleType(SyntaxNodeAnalysisContext context, TupleTypeS
 
         private static void CheckGenericName(SyntaxNodeAnalysisContext context, GenericNameSyntax genericNameSyntax, Location reportLocation)
         {
-            if (IsValueTuple(context, genericNameSyntax))
+            if (IsValueTupleWithLanguageRepresentation(context, genericNameSyntax))
             {
                 var location = reportLocation ?? genericNameSyntax.GetLocation();
                 context.ReportDiagnostic(Diagnostic.Create(Descriptor, location));
@@ -224,10 +230,12 @@ private static void CheckGenericName(SyntaxNodeAnalysisContext context, GenericN
             }
         }
 
-        private static bool IsValueTuple(SyntaxNodeAnalysisContext context, ExpressionSyntax syntax)
+        private static bool IsValueTupleWithLanguageRepresentation(SyntaxNodeAnalysisContext context, ExpressionSyntax syntax)
         {
             var symbolInfo = context.SemanticModel.GetSymbolInfo(syntax, context.CancellationToken);
-            return (symbolInfo.Symbol is ITypeSymbol typeSymbol) && typeSymbol.IsTupleType();
+            return symbolInfo.Symbol is INamedTypeSymbol typeSymbol
+                && typeSymbol.IsTupleType()
+                && typeSymbol.TupleElements().Length > 1;
         }
     }
 }