Fixed: Do not report AV1553 on interface implementations and overridden members (#141)

Author: bkoelman

src/CSharpGuidelinesAnalyzer/CSharpGuidelinesAnalyzer.Test/Specs/Maintainability/DoNotUseOptionalParameterWithDefaultValueNullSpecs.cs

@@ -215,6 +215,75 @@ await VerifyGuidelineDiagnosticAsync(source,
             "Optional parameter 'p' of type 'ValueTask<int>?' has default value 'null'");
     }
 
+    [Fact]
+    internal async Task When_method_implicitly_implements_interface_method_it_must_be_skipped()
+    {
+        // Arrange
+        ParsedSourceCode source = new TypeSourceCodeBuilder()
+            .WithReferenceToExternalAssemblyFor(@"
+                public interface I
+                {
+                    void M(string s = null);
+                }
+            ")
+            .InGlobalScope(@"
+                class C : I
+                {
+                    public void M(string s = null) => throw null;
+                }
+            ")
+            .Build();
+
+        // Act and assert
+        await VerifyGuidelineDiagnosticAsync(source);
+    }
+
+    [Fact]
+    internal async Task When_method_explicitly_implements_interface_method_it_must_be_skipped()
+    {
+        // Arrange
+        ParsedSourceCode source = new TypeSourceCodeBuilder()
+            .WithReferenceToExternalAssemblyFor(@"
+                public interface I
+                {
+                    void M(string s = null);
+                }
+            ")
+            .InGlobalScope(@"
+                class C : I
+                {
+                    void I.M(string s = null) => throw null;
+                }
+            ")
+            .Build();
+
+        // Act and assert
+        await VerifyGuidelineDiagnosticAsync(source);
+    }
+
+    [Fact]
+    internal async Task When_method_overrides_base_method_it_must_be_skipped()
+    {
+        // Arrange
+        ParsedSourceCode source = new TypeSourceCodeBuilder()
+            .WithReferenceToExternalAssemblyFor(@"
+                public abstract class B
+                {
+                    public virtual void M(string s = null) => throw null;
+                }
+            ")
+            .InGlobalScope(@"
+                class C : B
+                {
+                    public override void M(string s = null) => throw null;
+                }
+            ")
+            .Build();
+
+        // Act and assert
+        await VerifyGuidelineDiagnosticAsync(source);
+    }
+
     protected override DiagnosticAnalyzer CreateAnalyzer()
     {
         return new DoNotUseOptionalParameterWithDefaultValueNullAnalyzer();

src/CSharpGuidelinesAnalyzer/CSharpGuidelinesAnalyzer/Rules/Maintainability/DoNotUseOptionalParameterWithDefaultValueNullAnalyzer.cs

@@ -82,7 +82,8 @@ private static void AnalyzeParameter(SymbolAnalysisContext context, [NotNull] [I
         {
             var parameter = (IParameterSymbol)context.Symbol;
 
-            if (parameter.IsOptional && parameter.HasExplicitDefaultValue && parameter.ExplicitDefaultValue == null &&
+            if (parameter.IsOptional && parameter.HasExplicitDefaultValue && parameter.ExplicitDefaultValue == null && !parameter.ContainingSymbol.IsOverride &&
+                !parameter.ContainingSymbol.IsInterfaceImplementation() &&
                 !HasCallerArgumentExpressionAttribute(parameter, callerArgumentExpressionAttributeType))
             {
                 if (parameter.Type.IsOrImplementsIEnumerable() || IsTask(parameter.Type, taskTypes))