Add accessibility check in validation

Src/FastEnum.Tests.CodeGen/Code/TestHelper.cs

@@ -1,6 +1,7 @@
 using System.Collections.Immutable;
 using System.ComponentModel.DataAnnotations;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Text;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
@@ -39,7 +40,20 @@ public static string ReadResource(string name)
         return reader.ReadToEnd();
     }
 
-    public static string GetGeneratedOutput<T>(string source) where T : IIncrementalGenerator, new()
+    public static string GetGeneratedOutput<T>(string source, bool checkForErrors = true) where T : IIncrementalGenerator, new()
+    {
+        string res = GetGeneratedOutput<T>(source, out ImmutableArray<Diagnostic> codeGenDiag, out IEnumerable<Diagnostic> compilerDiag);
+
+        if (checkForErrors)
+            Assert.Empty(codeGenDiag);
+
+        if (checkForErrors)
+            Assert.Empty(compilerDiag);
+
+        return res;
+    }
+
+    public static string GetGeneratedOutput<T>(string source, out ImmutableArray<Diagnostic> codeGenDiag, out IEnumerable<Diagnostic> compilerDiag) where T : IIncrementalGenerator, new()
     {
         //Add a few headers by default
         source = GetHeader() + "\n" + source;
@@ -65,14 +79,10 @@ public static string ReadResource(string name)
 
         CSharpGeneratorDriver driver = CSharpGeneratorDriver.Create(generator);
 
-        driver.RunGeneratorsAndUpdateCompilation(compilation, out Compilation outputCompilation, out ImmutableArray<Diagnostic> diagnostics);
-        Assert.Empty(diagnostics); //CodeGen diagnostics
-
-        IEnumerable<Diagnostic> compilerDiag = outputCompilation.GetDiagnostics().Where(x => !_ignore.Contains(x.Id));
-        Assert.Empty(compilerDiag); //C# compiler diagnostics
+        driver.RunGeneratorsAndUpdateCompilation(compilation, out Compilation outputCompilation, out codeGenDiag);
+        compilerDiag = outputCompilation.GetDiagnostics().Where(x => !_ignore.Contains(x.Id));
 
         List<SyntaxTree> trees = outputCompilation.SyntaxTrees.ToList();
-        Assert.True(trees.Count > 1);
 
         StringBuilder sb = new StringBuilder();
 

Src/FastEnum.Tests.CodeGen/ValidationTests.cs

@@ -0,0 +1,26 @@
+using System.Collections.Immutable;
+using Genbox.FastEnum.Tests.CodeGen.Code;
+using Microsoft.CodeAnalysis;
+
+namespace Genbox.FastEnum.Tests.CodeGen;
+
+public class ValidationTests
+{
+    [Fact]
+    public void TestLessVisibleClass()
+    {
+        string code = """
+internal class MyInternalClass
+{
+    [FastEnum]
+    public enum MyPublicEnum1
+    {
+        Value
+    }
+}
+""";
+        TestHelper.GetGeneratedOutput<EnumGenerator>(code, out ImmutableArray<Diagnostic> codeGenDiag, out _);
+        Diagnostic res = Assert.Single(codeGenDiag);
+        Assert.Equal("FE001", res.Id); //Enum visibility validation failed
+    }
+}

Src/FastEnum/EnumGenerator.cs

@@ -39,7 +39,7 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
 
             if (!IsSpecsValid(specs, out string? message))
             {
-                DiagnosticDescriptor report = new DiagnosticDescriptor("ESG001", "FastEnum", $"Validation failed with message: {message}", "errors", DiagnosticSeverity.Error, true);
+                DiagnosticDescriptor report = new DiagnosticDescriptor("FE001", "FastEnum", $"Validation failed with message: {message}", "errors", DiagnosticSeverity.Error, true);
                 spc.ReportDiagnostic(Diagnostic.Create(report, Location.None));
                 return;
             }
@@ -124,8 +124,17 @@ private static bool IsSpecsValid(ImmutableArray<EnumSpec> specs, out string? mes
                 return false;
             }
 
-            //Now we need to satisfy C#'s invariant: parents must have equal or less accessibility than it's children
-            //TODO
+            //Now we need to satisfy C#'s invariant: parents must have equal or more visibility than it's children
+            if (es.AccessChain.Length > 1)
+            {
+                var parentAccess = es.AccessChain[1];
+
+                if (parentAccess < enumAccess)
+                {
+                    message = $"Parent class is less visible ({parentAccess}) than enum '{es.FullName} ({enumAccess}). That is not supported";
+                    return false;
+                }
+            }
         }
 
         message = null;
@@ -222,7 +231,7 @@ private static SourceText GetSource(StringBuilder sb, AssemblyName assemblyName,
 
         while (curSym != null)
         {
-            accessChain.Add(symbol.DeclaredAccessibility);
+            accessChain.Add(curSym.DeclaredAccessibility);
             curSym = curSym.ContainingSymbol;
         }