Fix 'use compound coalesce' analyzer in the presence of pp directives

src/Analyzers/CSharp/Analyzers/UseCompoundAssignment/CSharpUseCompoundCoalesceAssignmentDiagnosticAnalyzer.cs

@@ -132,7 +132,7 @@ private void AnalyzeIfStatement(SyntaxNodeAnalysisContext context)
             if (ifStatement.Else != null)
                 return;
 
-            if (!GetWhenTrueAssignment(ifStatement, out _, out var assignment))
+            if (!GetWhenTrueAssignment(ifStatement, out var whenTrue, out var assignment))
                 return;
 
             if (!IsReferenceEqualsNullCheck(semanticModel, ifStatement.Condition, cancellationToken, out var testedExpression))
@@ -153,24 +153,15 @@ private void AnalyzeIfStatement(SyntaxNodeAnalysisContext context)
                 return;
             }
 
-            if (ifStatement.Statement is BlockSyntax block)
-            {
-                // Single is safe here as GetWhenTrueAssignment will return null if we have a block without a single
-                // statement in it.
-                var firstStatement = block.Statements.Single();
-
-                // Don't want to offer anything if our if-statement body has any conditional directives in it.  That
-                // means there's some other code that may run under some other conditions, that we do not want to now
-                // run conditionally outside of the 'if' statement itself.
-                if (firstStatement.GetLeadingTrivia().Any(t => t.HasStructure && t.GetStructure() is ConditionalDirectiveTriviaSyntax))
-                    return;
-            }
+            // Don't want to offer anything if our if-statement body has any conditional directives in it.  That
+            // means there's some other code that may run under some other conditions, that we do not want to now
+            // run conditionally outside of the 'if' statement itself.
+            if (whenTrue.GetLeadingTrivia().Any(static t => t.GetStructure() is ConditionalDirectiveTriviaSyntax))
+                return;
 
+            // pointers cannot use ??=
             if (semanticModel.GetTypeInfo(testedExpression, cancellationToken).Type is IPointerTypeSymbol or IFunctionPointerTypeSymbol)
-            {
-                // pointers cannot use ??=
                 return;
-            }
 
             // Good match.
             context.ReportDiagnostic(DiagnosticHelper.Create(

src/Analyzers/CSharp/CodeFixes/UseCompoundAssignment/CSharpUseCompoundCoalesceAssignmentCodeFixProvider.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections.Immutable;
 using System.Composition;
 using System.Diagnostics.CodeAnalysis;
@@ -13,7 +12,6 @@
 using Microsoft.CodeAnalysis.CodeFixes;
 using Microsoft.CodeAnalysis.CSharp.Extensions;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
-using Microsoft.CodeAnalysis.CSharp.UseCoalesceExpression;
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.Editing;
 using Microsoft.CodeAnalysis.Formatting;

src/Analyzers/CSharp/Tests/UseCompoundAssignment/UseCompoundCoalesceAssignmentTests.cs

@@ -4,7 +4,6 @@
 
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CSharp;
-using Microsoft.CodeAnalysis.CSharp.Shared.Extensions;
 using Microsoft.CodeAnalysis.CSharp.UseCompoundAssignment;
 using Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions;
 using Microsoft.CodeAnalysis.Test.Utilities;
@@ -897,6 +896,46 @@ static void Main(object o)
                 """);
         }
 
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/63552")]
+        public async Task TestIfStatementWithPreprocessorBlock7()
+        {
+            await TestMissingAsync(
+                """
+                using System;
+                class C
+                {
+                    static void Main(object o)
+                    {
+                        if (o is null)
+                #if true
+                            o = "";
+                #endif
+                    }
+                }
+                """);
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/63552")]
+        public async Task TestIfStatementWithPreprocessorBlock8()
+        {
+            await TestMissingAsync(
+                """
+                using System;
+                class C
+                {
+                    static void Main(object o)
+                    {
+                        if (o is null)
+                #if true
+                            o = "";
+                #else
+                            o = "";
+                #endif
+                    }
+                }
+                """);
+        }
+
         [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/62473")]
         public async Task TestPointerCannotUseCoalesceAssignment()
         {