Fix source generator for class with parameterless private constructor.

Author: Bobris

BTDB.SourceGenerator.Sample/Examples.cs

@@ -14,11 +14,6 @@
     h(container, "Hello");
 }
 
-[GenerateFor(typeof(HttpContextAccessor))]
-interface xxx
-{
-}
-
 [Generate]
 public class DynamicEventWrapper
 {

BTDB.SourceGenerator.Test/IOCTests.VerifyIocRegistrationForParameterlessPrivateConstructor#Logger.g.verified.cs

@@ -0,0 +1,24 @@
+//HintName: Logger.g.cs
+// <auto-generated/>
+#pragma warning disable 612,618
+using System;
+using System.Runtime.CompilerServices;
+
+[CompilerGenerated]
+static file class LoggerRegistration
+{
+    [UnsafeAccessor(UnsafeAccessorKind.Constructor)]
+    extern static global::Logger Constr();
+    [ModuleInitializer]
+    internal static unsafe void Register4BTDB()
+    {
+        global::BTDB.IOC.IContainer.RegisterFactory(typeof(global::Logger), (container, ctx) =>
+        {
+            return (container2, ctx2) =>
+            {
+                var res = Constr();
+                return res;
+            };
+        });
+    }
+}

BTDB.SourceGenerator.Test/IOCTests.cs

@@ -230,6 +230,21 @@ private ErrorHandler(ILogger logger)
             """);
     }
 
+    [Fact]
+    public Task VerifyIocRegistrationForParameterlessPrivateConstructor()
+    {
+        // language=cs
+        return VerifySourceGenerator("""
+            [BTDB.Generate]
+            public class Logger
+            {
+                private Logger()
+                {
+                }
+            }
+            """);
+    }
+
     [Fact]
     public Task VerifyIocRegistrationForDependencyProperties()
     {

BTDB.SourceGenerator/Main.cs

@@ -286,6 +286,7 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                 if (symbolConstructor.Parameters.Length == 0)
                 {
                     hasDefaultConstructor = true;
+                    constructor ??= symbolConstructor;
                 }
 
                 if (symbolConstructor.Parameters.Length > (constructor?.Parameters.Length ?? 0))