Add test for SA1000's handling of c# 7.1 default literal expressions

#2420

Author: bjornhellander

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp7/SpacingRules/SA1000CSharp7UnitTests.cs

@@ -252,5 +252,27 @@ public async Task TestStackAllocImplicitArrayStatementAsync()
             // this case is handled by SA1026, so it shouldn't be reported here
             await this.TestKeywordStatementAsync(statementWithSpace, DiagnosticResult.EmptyDiagnosticResults, statementWithSpace, languageVersion: LanguageVersion.CSharp7_3.OrLaterDefault()).ConfigureAwait(false);
         }
+
+        [Theory]
+        [InlineData("var x = b ? default : 3;")]
+        [InlineData("var x = b ?default: 3;")]
+        [InlineData("int x = default;")]
+        [InlineData("int x =default ;")]
+        [WorkItem(2420, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/2420")]
+        public async Task TestDefaultLiteralExpressionAsync(string statement)
+        {
+            var testCode = $@"namespace TestNamespace
+{{
+    public class TestClass
+    {{
+        public void TestMethod(bool b)
+        {{
+            {statement}
+        }}
+    }}
+}}";
+
+            await VerifyCSharpDiagnosticAsync(LanguageVersion.CSharp7_1.OrLaterDefault(), testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }

StyleCop.Analyzers/StyleCop.Analyzers/SpacingRules/SA1000KeywordsMustBeSpacedCorrectly.cs

@@ -1,8 +1,6 @@
 // Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-#nullable disable
-
 namespace StyleCop.Analyzers.SpacingRules
 {
     using System;
@@ -143,7 +141,7 @@ private static void HandleSyntaxTree(SyntaxTreeAnalysisContext context)
                 case SyntaxKind.DefaultKeyword:
                     if (token.Parent.IsKind(SyntaxKindEx.DefaultLiteralExpression))
                     {
-                        // Ignore spacing around a default literal expression for now
+                        // Ignore spacing around a default literal expression
                         break;
                     }
 

documentation/SA1000.md

@@ -27,7 +27,9 @@ The following C# keywords should always be followed by a single space: `and`, `a
 `foreach`, `from`, `group`, `if`, `in`, `is`, `into`, `join`, `let`, `lock`, `not`, `orderby`, `or`, `out`, `ref`, `return`, `select`,
 `switch`, `using`, `var`, `where`, `while`, `yield`.
 
-The following keywords should not be followed by any space: `checked`, `default`, `nameof`, `sizeof`, `typeof`, `unchecked`.
+The `checked`, `default`, `nameof`, `sizeof`, `typeof`, and `unchecked` keywords should not be followed by any space, except in the following cases:
+
+* The `default` keyword is used as a c# 7.1 default literal expression. In this case it can both have and not have trailing spaces.
 
 The `new` and `stackalloc` keywords should always be followed by a space, except in the following cases: