Generate valid C# for typedef-ed type parameters

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

Author: ddobrev

src/Generator/Generators/CSharp/CSharpMarshal.cs

@@ -217,32 +217,37 @@ public override bool VisitPrimitiveType(PrimitiveType primitive, TypeQualifiers
 
         public override bool VisitTypedefType(TypedefType typedef, TypeQualifiers quals)
         {
-            if (!VisitType(typedef, quals))
+            if (!(typedef.Declaration.Type.Desugar(false) is TemplateParameterSubstitutionType) &&
+                !VisitType(typedef, quals))
                 return false;
 
             var decl = typedef.Declaration;
 
-            var functionType = decl.Type as FunctionType;
-            if (functionType != null || decl.Type.IsPointerTo(out functionType))
-            {
-                var ptrName = $"{Generator.GeneratedIdentifier("ptr")}{Context.ParameterIndex}";
-
-                Context.Before.WriteLine($"var {ptrName} = {Context.ReturnVarName};");
-
-                var specialization = decl.Namespace as ClassTemplateSpecialization;
-                Type returnType = Context.ReturnType.Type.Desugar();
-                var finalType = (returnType.GetFinalPointee() ?? returnType).Desugar();
-                var res = string.Format(
-                    "{0} == IntPtr.Zero? null : {1}({2}) Marshal.GetDelegateForFunctionPointer({0}, typeof({2}))",
-                    ptrName,
-                    finalType.IsDependent ? $@"({specialization.TemplatedDecl.TemplatedClass.Typedefs.First(
-                        t => t.Name == decl.Name).Visit(this.typePrinter)}) (object) " : string.Empty,
-                    typedef);
-                Context.Return.Write(res);
-                return true;
-            }
+            Type type = decl.Type.Desugar();
+            var functionType = type as FunctionType;
+            if (functionType == null && !type.IsPointerTo(out functionType))
+                return decl.Type.Visit(this);
+
+            var ptrName = $@"{Generator.GeneratedIdentifier("ptr")}{
+                Context.ParameterIndex}";
 
-            return decl.Type.Visit(this);
+            Context.Before.WriteLine($"var {ptrName} = {Context.ReturnVarName};");
+
+            var substitution = decl.Type.Desugar(false)
+                as TemplateParameterSubstitutionType;
+
+            if (substitution != null)
+                Context.Return.Write($@"({
+                    substitution.ReplacedParameter.Parameter.Name}) (object) (");
+
+            Context.Return.Write($@"{ptrName} == IntPtr.Zero? null : {
+                (substitution == null ? $"({Context.ReturnType}) " :
+                 string.Empty)}Marshal.GetDelegateForFunctionPointer({
+                ptrName}, typeof({typedef}))");
+
+            if (substitution != null)
+                Context.Return.Write(")");
+            return true;
         }
 
         public override bool VisitFunctionType(FunctionType function, TypeQualifiers quals)

tests/CSharp/CSharpTemplates.h

@@ -32,6 +32,7 @@ class DLL_API Ignored
 template <typename T>
 class DLL_API IndependentFields : public T1
 {
+    typedef T Type;
 public:
     IndependentFields();
     IndependentFields(const IndependentFields<T>& other);
@@ -44,6 +45,7 @@ class DLL_API IndependentFields : public T1
     int getIndependent();
     const T* returnTakeDependentPointer(const T* p);
     T getDependent(const T& t);
+    Type property();
     const T* propertyReturnDependentPointer();
     static T staticDependent(const T& t);
     void hasDefaultDependentParam(T* ptr, const T& refT = T());
@@ -111,6 +113,12 @@ T IndependentFields<T>::getDependent(const T& t)
     return t;
 }
 
+template <typename T>
+T IndependentFields<T>::property()
+{
+    return T();
+}
+
 template <typename T>
 const T* IndependentFields<T>::propertyReturnDependentPointer()
 {