Add more checks and test cases

Author: captainsafia

src/Framework/AspNetCoreAnalyzers/src/SourceGenerators/PublicTopLevelProgramGenerator.cs

@@ -20,6 +20,14 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             {
                 return null;
             }
+            // If the discovered `Program` type is an interface, struct or generic type then its not
+            // generated and has been defined in source, so we can skip it
+            if (program.TypeKind == TypeKind.Struct || program.TypeKind == TypeKind.Interface || program.IsGenericType)
+            {
+                return null;
+            }
+            // If there are multiple partial declarations, then do nothing since we don't want
+            // to trample on visibility explicitly set by the user
             if (program.DeclaringSyntaxReferences.Length > 1)
             {
                 return null;

src/Framework/AspNetCoreAnalyzers/test/SourceGenerators/PublicTopLevelProgramGeneratorTests.cs

@@ -46,6 +46,24 @@ public partial class Program { }
         await VerifyCS.VerifyAsync(source);
     }
 
+    [Fact]
+    public async Task DoesNotGeneratesSource_IfProgramDeclaresExplicitInternalAccess()
+    {
+        var source = """
+using Microsoft.AspNetCore.Builder;
+
+var app = WebApplication.Create();
+
+app.MapGet("/", () => "Hello, World!");
+
+app.Run();
+
+internal partial class Program { }
+""";
+
+        await VerifyCS.VerifyAsync(source);
+    }
+
     [Fact]
     public async Task DoesNotGeneratorSource_ExplicitPublicProgramClass()
     {
@@ -85,6 +103,30 @@ public static void Main()
         app.Run();
     }
 }
+""";
+
+        await VerifyCS.VerifyAsync(source);
+    }
+
+    [Theory]
+    [InlineData("interface")]
+    [InlineData("struct")]
+    public async Task DoesNotGeneratorSource_ExplicitInternalProgramType(string type)
+    {
+        var source = $$"""
+using Microsoft.AspNetCore.Builder;
+
+internal {{type}} Program
+{
+    public static void Main(string[] args)
+    {
+        var app = WebApplication.Create();
+
+        app.MapGet("/", () => "Hello, World!");
+
+        app.Run();
+    }
+}
 """;
 
         await VerifyCS.VerifyAsync(source);