Fix analyzer RCS1096

ChangeLog.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix analyzer [RCS0053](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS0053) ([PR](https://github.com/dotnet/roslynator/pull/1547))
 - Fix analyzer [RCS1223](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1223) ([PR](https://github.com/dotnet/roslynator/pull/1552))
 - Fix analyzer [RCS1140](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1140) ([PR](https://github.com/dotnet/roslynator/pull/1554))
+- Fix analyzer [RCS1096](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1096) ([PR](https://github.com/dotnet/roslynator/pull/1558))
 - [CLI] Improve removing of unused symbols ([PR](https://github.com/dotnet/roslynator/pull/1550))
 
 ## [4.12.7] - 2024-10-01

src/Analyzers/CSharp/Analysis/UseHasFlagMethodOrBitwiseOperatorAnalyzer.cs

@@ -79,8 +79,20 @@ private static void AnalyzeBitwiseAndExpression(SyntaxNodeAnalysisContext contex
 
         if (otherExpression.IsNumericLiteralExpression("0"))
         {
-            if (SyntaxUtility.IsCompositeEnumValue(right, semanticModel, cancellationToken))
-                return;
+            var enumTypeSymbol = (INamedTypeSymbol)semanticModel.GetTypeSymbol(right, cancellationToken);
+
+            if (enumTypeSymbol?.EnumUnderlyingType is not null)
+            {
+                Optional<object> constantValue = semanticModel.GetConstantValue(right, cancellationToken);
+
+                if (!constantValue.HasValue)
+                    return;
+
+                ulong value = SymbolUtility.GetEnumValueAsUInt64(constantValue.Value!, enumTypeSymbol);
+
+                if (FlagsUtility<ulong>.Instance.IsComposite(value))
+                    return;
+            }
         }
         else if (!CSharpFactory.AreEquivalent(right, otherExpression))
         {

src/Tests/Analyzers.Tests/RCS1096UseHasFlagMethodOrBitwiseOperatorTests.cs

@@ -267,6 +267,28 @@ bool M(int value)
         return (value & (value - 1)) == 0;
     }
 }
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseHasFlagMethodOrBitwiseOperator)]
+    public async Task TestNoDiagnostic_NotConstant()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System.IO;
+
+class P
+{
+    private  FileAttributes _flags = FileAttributes.Device | FileAttributes.Offline;
+
+    void M()
+    {
+        var flag = FileAttributes.Device;
+
+        if ((flag & _flags) != 0)
+        {
+        }
+    }
+}
 ");
     }
 }