From 27374633e5defa26b86bcd6d932e9f77739150e3 Mon Sep 17 00:00:00 2001
From: Youssef1313 <youssefvictor00@gmail.com>
Date: Thu, 7 Jul 2022 21:22:23 +0200
Subject: [PATCH] Don't offer '??=' for pointer types

---
 ...undCoalesceAssignmentDiagnosticAnalyzer.cs |  7 ++-
 .../UseCompoundCoalesceAssignmentTests.cs     | 44 +++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/Analyzers/CSharp/Analyzers/UseCompoundAssignment/CSharpUseCompoundCoalesceAssignmentDiagnosticAnalyzer.cs b/src/Analyzers/CSharp/Analyzers/UseCompoundAssignment/CSharpUseCompoundCoalesceAssignmentDiagnosticAnalyzer.cs
index b3e9e5ed27283..a54b3856d9231 100644
--- a/src/Analyzers/CSharp/Analyzers/UseCompoundAssignment/CSharpUseCompoundCoalesceAssignmentDiagnosticAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analyzers/UseCompoundAssignment/CSharpUseCompoundCoalesceAssignmentDiagnosticAnalyzer.cs
@@ -5,7 +5,6 @@
 using System;
 using System.Collections.Immutable;
 using System.Diagnostics.CodeAnalysis;
-using System.Linq.Expressions;
 using System.Threading;
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
@@ -153,6 +152,12 @@ private void AnalyzeIfStatement(SyntaxNodeAnalysisContext context)
                 return;
             }
 
+            if (semanticModel.GetTypeInfo(testedExpression, cancellationToken).Type.IsPointerType())
+            {
+                // pointers cannot use ??=
+                return;
+            }
+
             // Good match.
             context.ReportDiagnostic(DiagnosticHelper.Create(
                 Descriptor,
diff --git a/src/Analyzers/CSharp/Tests/UseCompoundAssignment/UseCompoundCoalesceAssignmentTests.cs b/src/Analyzers/CSharp/Tests/UseCompoundAssignment/UseCompoundCoalesceAssignmentTests.cs
index 9b480405e8d68..071bf2571dc3a 100644
--- a/src/Analyzers/CSharp/Tests/UseCompoundAssignment/UseCompoundCoalesceAssignmentTests.cs
+++ b/src/Analyzers/CSharp/Tests/UseCompoundAssignment/UseCompoundCoalesceAssignmentTests.cs
@@ -694,5 +694,49 @@ static void Main(object o)
     }
 }");
         }
+
+        [WorkItem(62473, "https://github.com/dotnet/roslyn/issues/62473")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCompoundAssignment)]
+        public async Task TestPointerCannotUseCoalesceAssignment()
+        {
+            // The purpose of this test is to keep track of whether the language
+            // allows ??= for pointers in future. It should be kept in 'Preview'.
+            // If the test failed because language added support and this is no longer
+            // an error. The behavior for test 'TestPointer' below should be updated as well to suggest ??=
+            // Note that, when ??= is supported for pointers, the analyzer should check the language version which supports it.
+            await TestMissingAsync("""
+                unsafe class Program
+                {
+                    private static void Main()
+                    {
+                        byte* ptr = null;
+                        {|CS0019:ptr ??= Get()|};
+                    }
+
+                    static byte* Get() => null;
+                }
+                """, LanguageVersion.Preview);
+        }
+
+        [WorkItem(62473, "https://github.com/dotnet/roslyn/issues/62473")]
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsUseCompoundAssignment)]
+        public async Task TestPointer()
+        {
+            await TestMissingAsync("""
+                unsafe class Program
+                {
+                    private static void Main()
+                    {
+                        byte* ptr = null;
+                        if (ptr is null)
+                        {
+                            ptr = Get();
+                        }
+                    }
+
+                    static byte* Get() => null;
+                }
+                """, LanguageVersion.Preview);
+        }
     }
 }