Fix FP

SonarSource · Jul 4, 2024 · f19c0eb · f19c0eb
1 parent a5d372d
commit f19c0eb
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Showing 2 changed files with 31 additions and 7 deletions.
diff --git a/...onarAnalyzer.Common/SymbolicExecution/Roslyn/OperationProcessors/Invocation.Enumerable.cs b/...onarAnalyzer.Common/SymbolicExecution/Roslyn/OperationProcessors/Invocation.Enumerable.cs
@@ -87,18 +87,34 @@ private static ProgramState[] ProcessLinqEnumerableAndQueryable(ProgramState sta
             return states.Select(x => x.SetOperationConstraint(invocation, ObjectConstraint.NotNull)).ToArray();
         }
         // ElementAtOrDefault is intentionally not supported. It's causing many FPs
-        else if (name is nameof(Enumerable.FirstOrDefault) or nameof(Enumerable.LastOrDefault) or nameof(Enumerable.SingleOrDefault))
+        else if (name is nameof(Enumerable.FirstOrDefault) or nameof(Enumerable.LastOrDefault) or nameof(Enumerable.SingleOrDefault)
+                && invocation.TryGetInstance(state) is { } instance
+                && instance.TrackedSymbol(state) is { } instanceSymbol
+                && GetElementType(instanceSymbol) is { } elementType)
         {
-            return states.SelectMany(x => new List<ProgramState>
-            {
-                x.SetOperationConstraint(invocation, ObjectConstraint.Null),
-                x.SetOperationConstraint(invocation, ObjectConstraint.NotNull)
-            }).ToArray();
+            return states.SelectMany(x => ProcessElementOrDefaultMethods(x, invocation, elementType, instanceSymbol)).ToArray();
         }
         else
         {
             return states;
         }
+
+        static IEnumerable<ProgramState> ProcessElementOrDefaultMethods(ProgramState state, IInvocationOperationWrapper invocation, ITypeSymbol elementType, ISymbol instanceSymbol) =>
+            state[instanceSymbol]?.Constraint<CollectionConstraint>() switch
+            {
+                CollectionConstraint constraint when constraint == CollectionConstraint.Empty && elementType.IsReferenceType => [state.SetOperationConstraint(invocation, ObjectConstraint.Null)],
+                CollectionConstraint constraint when constraint == CollectionConstraint.NotEmpty && elementType.IsReferenceType =>
+                    [
+                        state,
+                        state.SetOperationConstraint(invocation, ObjectConstraint.NotNull)
+                    ],
+                _ when elementType.IsReferenceType =>
+                    [
+                        state.SetOperationConstraint(invocation, ObjectConstraint.Null),
+                        state.SetOperationConstraint(invocation, ObjectConstraint.NotNull)
+                    ],
+                _ => state.SetOperationConstraint(invocation, ObjectConstraint.NotNull).ToArray()
+            };
     }
 
     private static ProgramState[] ProcessBoolCollectionMethods(ProgramState state, IInvocationOperationWrapper invocation)
@@ -129,4 +145,12 @@ static bool HasNoParameters(IMethodSymbol symbol) =>
             (symbol.IsExtensionMethod && symbol.Parameters.Length == 1)
             || symbol.Parameters.IsEmpty;
     }
+
+    private static ITypeSymbol GetElementType(ISymbol instance) =>
+        instance.GetSymbolType() switch
+        {
+            INamedTypeSymbol { TypeArguments: { Length: 1 } typeArguments } => typeArguments.First(),
+            IArrayTypeSymbol arrayType => arrayType.ElementType,
+            _ => null
+        };
 }
diff --git a/...ers/tests/SonarAnalyzer.Test/TestCases/SymbolicExecution/Roslyn/NullPointerDereference.cs b/...ers/tests/SonarAnalyzer.Test/TestCases/SymbolicExecution/Roslyn/NullPointerDereference.cs
@@ -2085,7 +2085,7 @@ void Method(Exception[] array)
         if (array.Any())
         {
             Exception exception = array.FirstOrDefault();
-            Console.WriteLine(exception.Message); // Noncompliant - FP
+            Console.WriteLine(exception.Message); // Compliant - we know that array is not empty
         }
     }
 }