WPF0041 don't warn when private

Fix #376

Author: JohanLarsson

ValidCode/Issues/Issue376.cs

@@ -0,0 +1,23 @@
+namespace ValidCode.Issues;
+
+using System.Windows;
+
+public class Issue376 : FrameworkElement
+{
+    private static readonly DependencyProperty TextProperty = DependencyProperty.Register(
+        nameof(Text),
+        typeof(string),
+        typeof(Issue376),
+        new PropertyMetadata(default(string)));
+
+    private string? Text
+    {
+        get => (string?)this.GetValue(TextProperty);
+        set => this.SetValue(TextProperty, value);
+    }
+
+    public void M(string text)
+    {
+        this.Text = text;
+    }
+}

WpfAnalyzers.Test/WPF0041SetMutableUsingSetCurrentValueTests/Valid.cs

@@ -776,4 +776,36 @@ public bool IsTrue
 
         RoslynAssert.Valid(Analyzer, boxes, code);
     }
+
+    [Test]
+    public static void WhenPrivate()
+    {
+        var code = @"
+namespace ValidCode.Issues;
+
+using System.Windows;
+
+public class Issue376 : FrameworkElement
+{
+    private static readonly DependencyProperty TextProperty = DependencyProperty.Register(
+        nameof(Text),
+        typeof(string),
+        typeof(Issue376),
+        new PropertyMetadata(default(string)));
+
+    private string? Text
+    {
+        get => (string?)this.GetValue(TextProperty);
+        set => this.SetValue(TextProperty, value);
+    }
+
+    public void M(string text)
+    {
+        this.Text = text;
+    }
+}
+";
+
+        RoslynAssert.Valid(Analyzer, code);
+    }
 }

WpfAnalyzers/WPF0041SetMutableUsingSetCurrentValue.cs

@@ -49,7 +49,8 @@ private static void HandleAssignment(SyntaxNodeAnalysisContext context)
         static bool IsIgnored(IPropertySymbol property)
         {
             return property == KnownSymbols.FrameworkElement.DataContext ||
-                   property == KnownSymbols.FrameworkElement.Style;
+                   property == KnownSymbols.FrameworkElement.Style ||
+                   property.DeclaredAccessibility == Accessibility.Private;
         }
     }