Allow static class conversion for classes with implicitly defined constructor

src/Generator.Tests/Passes/TestPasses.cs

@@ -66,6 +66,29 @@ namespace CppSharp.Generator.Tests.Passes
             Assert.IsTrue(ucharClassEnum.BuiltinType.Type == PrimitiveType.UChar);
         }
 
+        [Test]
+        public void TestCheckStaticClassPass()
+        {
+            var staticClass = AstContext.Class("TestCheckStaticClass");
+            var staticStruct = AstContext.Class("TestCheckStaticStruct");
+            var staticClassDeletedCtor = AstContext.Class("TestCheckStaticClassDeleted");
+            var nonStaticClass = AstContext.Class("TestCheckNonStaticClass");
+
+            Assert.IsFalse(staticClass.IsStatic);
+            Assert.IsFalse(staticStruct.IsStatic);
+            Assert.IsFalse(staticClassDeletedCtor.IsStatic);
+            Assert.IsFalse(nonStaticClass.IsStatic);
+
+            passBuilder.AddPass(new CheckStaticClassPass());
+            passBuilder.RunPasses(pass => pass.VisitASTContext(AstContext));
+
+            Assert.IsTrue(staticClass.IsStatic, "`TestCheckStaticClass` should be static");
+            Assert.IsTrue(staticStruct.IsStatic, "`TestCheckStaticStruct` should be static");
+            Assert.IsTrue(staticClassDeletedCtor.IsStatic, "`TestCheckStaticClassDeleted` should be static");
+
+            Assert.IsFalse(nonStaticClass.IsStatic, "`TestCheckNonStaticClass` should NOT be static, since it has a private data field with default ctor");
+        }
+
         [Test]
         public void TestFunctionToInstancePass()
         {

src/Generator/Driver.cs

@@ -230,7 +230,7 @@ namespace CppSharp
 
             passes.AddPass(new FindSymbolsPass());
             passes.AddPass(new CheckMacroPass());
-            passes.AddPass(new CheckStaticClass());
+            passes.AddPass(new CheckStaticClassPass());
 
             if (Options.IsCLIGenerator || Options.IsCSharpGenerator || Options.IsCppGenerator)
             {

src/Generator/Passes/CheckStaticClassPass.cs

@@ -7,9 +7,9 @@ namespace CppSharp.Passes
     /// <summary>
     /// Checks for classes that should be bound as static classes.
     /// </summary>
-    public class CheckStaticClass : TranslationUnitPass
+    public class CheckStaticClassPass : TranslationUnitPass
     {
-        public CheckStaticClass()
+        public CheckStaticClassPass()
             => VisitOptions.ResetFlags(VisitFlags.ClassMethods);
 
         public override bool VisitDeclaration(Declaration decl)
@@ -69,13 +69,34 @@ namespace CppSharp.Passes
 
         public override bool VisitClassDecl(Class @class)
         {
-            // If the class has any non-private constructors then it cannot
-            // be bound as a static class and we bail out early.
-            if (@class.Constructors.Any(m =>
-                !(m.IsCopyConstructor || m.IsMoveConstructor)
-                && m.Access != AccessSpecifier.Private))
+            // If the class is to be used as an opaque type, then it cannot be
+            // bound as static.
+            if (@class.IsOpaque)
+                return false;
+
+            if (@class.IsDependent)
                 return false;
 
+            if (@class.Constructors.Any(m =>
+                {
+                    // Implicit constructors are not user-defined, so assume this was unintentional.
+                    if (m.IsImplicit)
+                        return false;
+
+                    // Ignore deleted constructors.
+                    if (m.IsDeleted)
+                        return false;
+
+                    // If the class has a copy or move constructor, it cannot be static.
+                    if (m.IsCopyConstructor || m.IsMoveConstructor)
+                        return true;
+
+                    // If the class has any (user defined) non-private constructors then it cannot be static
+                    return m.Access != AccessSpecifier.Private;
+                }))
+            {
+                return false;
+            }
             // Check for any non-static fields or methods, in which case we
             // assume the class is not meant to be static.
             // Note: Static fields are represented as variables in the AST.
@@ -86,20 +107,12 @@ namespace CppSharp.Passes
 
             // Check for any static function that return a pointer to the class.
             // If one exists, we assume it's a factory function and the class is
-            // not meant to be static. It's a simple heuristic but it should be
+            // not meant to be static. It's a simple heuristic, but it should be
             // good enough for the time being.
             if (@class.Functions.Any(m => !m.IsOperator && ReturnsClassInstance(m)) ||
                 @class.Methods.Any(m => !m.IsOperator && ReturnsClassInstance(m)))
                 return false;
 
-            // If the class is to be used as an opaque type, then it cannot be
-            // bound as static.
-            if (@class.IsOpaque)
-                return false;
-
-            if (@class.IsDependent)
-                return false;
-
             // TODO: We should take C++ friends into account here, they might allow
             // a class to be instantiated even it if's not possible to instantiate
             // it using just its regular members.

tests/dotnet/Native/Passes.h

@@ -130,6 +130,60 @@ struct TestCheckAmbiguousFunctionsPass
     int Method(int x) const;
 };
 
+class TestCheckStaticClass
+{
+public:
+    static int Method();
+    static int Method(int x);
+
+    constexpr static float ConstExprStatic = 3.0f;
+    inline static float InlineStatic = 1.0f;
+
+private:
+    inline static float PrivateInlineStatic = 1.0f;
+};
+
+struct TestCheckStaticStruct
+{
+    static int Method();
+    static int Method(int x);
+
+    constexpr static float ConstExprStatic = 3.0f;
+    inline static float InlineStatic = 1.0f;
+};
+
+class TestCheckStaticClassDeleted
+{
+public:
+    TestCheckStaticClassDeleted() = delete;
+
+    static int Method();
+    static int Method(int x);
+
+    constexpr static float ConstExprStatic = 3.0f;
+    inline static float InlineStatic = 1.0f;
+
+private:
+    inline static float PrivateInlineStatic = 1.0f;
+};
+
+class TestCheckNonStaticClass
+{
+public:
+    TestCheckNonStaticClass() = default;
+
+    static int Method();
+    static int Method(int x);
+
+    constexpr static float ConstExprStatic = 3.0f;
+    inline static float InlineStatic = 1.0f;
+
+private:
+    inline static float PrivateInlineStatic = 1.0f;
+
+    float NonStatic = 1.0f;
+};
+
 #define CS_INTERNAL
 struct TestMethodAsInternal
 {