Generate valid C# for template indexers taking const char*

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

src/AST/Type.cs

@@ -866,10 +866,12 @@ namespace CppSharp.AST
             var type = obj as TemplateParameterSubstitutionType;
             if (type == null) return false;
 
-            return Replacement.Equals(type.Replacement);
+            return ReplacedParameter.Equals(type.ReplacedParameter) &&
+                Replacement.Equals(type.Replacement);
         }
 
-        public override int GetHashCode() => Replacement.GetHashCode();
+        public override int GetHashCode() =>
+            ReplacedParameter.GetHashCode() ^ Replacement.GetHashCode();
     }
 
     /// <summary>

src/Generator/Generators/CSharp/CSharpMarshal.cs

@@ -312,7 +312,8 @@ namespace CppSharp.Generators.CSharp
             Type finalType = (returnType.GetFinalPointee() ?? returnType).Desugar();
             if (finalType.IsDependent)
                 Context.Return.Write($"({param.ReplacedParameter.Parameter.Name}) (object) ");
-            if (param.Replacement.Type.Desugar().IsPointerToPrimitiveType())
+            Type replacement = param.Replacement.Type.Desugar();
+            if (replacement.IsPointerToPrimitiveType() && !replacement.IsConstCharString())
                 Context.Return.Write($"({typePrinter.IntPtrType}) ");
             return base.VisitTemplateParameterSubstitutionType(param, quals);
         }
@@ -623,9 +624,10 @@ namespace CppSharp.Generators.CSharp
         public override bool VisitTemplateParameterSubstitutionType(TemplateParameterSubstitutionType param, TypeQualifiers quals)
         {
             var replacement = param.Replacement.Type.Desugar();
-            if (replacement.IsPrimitiveType() ||
-                replacement.IsPointerToPrimitiveType() ||
-                replacement.IsEnum())
+            if ((replacement.IsPrimitiveType() ||
+                 replacement.IsPointerToPrimitiveType() ||
+                 replacement.IsEnum()) &&
+                !replacement.IsConstCharString())
             {
                 Context.Return.Write($"({replacement}) ");
                 if (replacement.IsPointerToPrimitiveType())

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -1049,15 +1049,15 @@ namespace CppSharp.Generators.CSharp
             if (type.IsPrimitiveType())
             {
                 WriteLine($@"*{@internal}.{internalFunction}({
-                    GetInstanceParam(function)}, {(paramMarshal.Context == null ?
-                    paramMarshal.Name : paramMarshal.Context.Return)}) = {marshal.Context.Return};");
+                    GetInstanceParam(function)}, {paramMarshal.Context.ArgumentPrefix}{
+                    paramMarshal.Name}) = {marshal.Context.Return};");
             }
             else
             {
                 var typeInternal = TypePrinter.PrintNative(type);
                 WriteLine($@"*({typeInternal}*) {@internal}.{internalFunction}({
-                    GetInstanceParam(function)}, {(paramMarshal.Context == null ?
-                    paramMarshal.Name : paramMarshal.Context.Return)}) = {marshal.Context.Return};");
+                    GetInstanceParam(function)}, {paramMarshal.Context.ArgumentPrefix}{
+                    paramMarshal.Name}) = {marshal.Context.Return};");
             }
         }
 

src/Generator/Generators/CSharp/CSharpSourcesExtensions.cs

@@ -139,7 +139,7 @@ namespace CppSharp.Generators.CSharp
                 i =>
                 {
                     CppSharp.AST.Type type = specialization.Arguments[i].Type.Type;
-                    return type.IsPointerToPrimitiveType() ?
+                    return type.IsPointerToPrimitiveType() && !type.IsConstCharString() ?
                         $"__{@class.TemplateParameters[i].Name}.FullName == \"System.IntPtr\"" :
                         $"__{@class.TemplateParameters[i].Name}.IsAssignableFrom(typeof({type}))";
                 })));

src/Generator/Types/Std/Stdlib.cs

@@ -167,24 +167,31 @@ namespace CppSharp.Types.Std
 
         public override void CSharpMarshalToNative(CSharpMarshalContext ctx)
         {
+            string param = ctx.Parameter.Name;
             if (ctx.Parameter.Usage == ParameterUsage.Unknown &&
                 !ctx.Parameter.Type.IsReference() &&
+                !(ctx.Parameter.Type is TemplateParameterSubstitutionType) &&
                 ctx.MarshalKind != MarshalKind.NativeField &&
                 ctx.MarshalKind != MarshalKind.VTableReturnValue &&
                 ctx.MarshalKind != MarshalKind.Variable)
             {
-                ctx.Return.Write(ctx.Parameter.Name);
+                ctx.Return.Write(param);
                 return;
             }
+
+            var substitution = Type as TemplateParameterSubstitutionType;
+            if (substitution != null)
+                param = $"({substitution.Replacement}) (object) {param}";
+
             if (Equals(Context.Options.Encoding, Encoding.ASCII))
             {
-                ctx.Return.Write($"Marshal.StringToHGlobalAnsi({ctx.Parameter.Name})");
+                ctx.Return.Write($"Marshal.StringToHGlobalAnsi({param})");
                 return;
             }
             if (Equals(Context.Options.Encoding, Encoding.Unicode) ||
                 Equals(Context.Options.Encoding, Encoding.BigEndianUnicode))
             {
-                ctx.Return.Write($"Marshal.StringToHGlobalUni({ctx.Parameter.Name})");
+                ctx.Return.Write($"Marshal.StringToHGlobalUni({param})");
                 return;
             }
             throw new System.NotSupportedException(
@@ -200,7 +207,7 @@ namespace CppSharp.Types.Std
                 return;
             }
 
-            Type type = ctx.ReturnType.Type.Desugar();
+            Type type = Type.Desugar();
             Type pointee = type.GetPointee().Desugar();
             var isChar = type.IsPointerToPrimitiveType(PrimitiveType.Char) ||
                 (pointee.IsPointerToPrimitiveType(PrimitiveType.Char) &&
@@ -211,27 +218,31 @@ namespace CppSharp.Types.Std
             if (Equals(encoding, Encoding.ASCII))
                 encoding = Context.Options.Encoding;
 
+            string returnVarName = ctx.Function != null &&
+                ctx.Function.ReturnType.Type.Desugar().IsAddress() ?
+                $"(global::System.IntPtr) {ctx.ReturnVarName}" : ctx.ReturnVarName;
+
             if (Equals(encoding, Encoding.ASCII))
             {
-                ctx.Return.Write($"Marshal.PtrToStringAnsi({ctx.ReturnVarName})");
+                ctx.Return.Write($"Marshal.PtrToStringAnsi({returnVarName})");
                 return;
             }
             if (Equals(encoding, Encoding.UTF8))
             {
-                ctx.Return.Write($"Marshal.PtrToStringUTF8({ctx.ReturnVarName})");
+                ctx.Return.Write($"Marshal.PtrToStringUTF8({returnVarName})");
                 return;
             }
 
             // If we reach this, we know the string is Unicode.
             if (isChar || ctx.Context.TargetInfo.WCharWidth == 16)
             {
-                ctx.Return.Write($"Marshal.PtrToStringUni({ctx.ReturnVarName})");
+                ctx.Return.Write($"Marshal.PtrToStringUni({returnVarName})");
                 return;
             }
             // If we reach this, we should have an UTF-32 wide string.
             const string encodingName = "System.Text.Encoding.UTF32";
             ctx.Return.Write($@"CppSharp.Runtime.Helpers.MarshalEncodedString({
-                ctx.ReturnVarName}, {encodingName})");
+                returnVarName}, {encodingName})");
         }
     }
 

tests/CSharp/CSharpTemplates.h

@@ -715,7 +715,8 @@ void forceUseSpecializations(IndependentFields<int> _1, IndependentFields<bool>
                              TemplateDerivedFromRegularDynamic<RegularDynamic> _14,
                              IndependentFields<OnlySpecialisedInTypeArg<double>> _15,
                              DependentPointerFields<float> _16, IndependentFields<const T1&> _17,
-                             TemplateWithIndexer<T2*> _18, IndependentFields<int(*)(int)>, std::string s);
+                             TemplateWithIndexer<T2*> _18, IndependentFields<int(*)(int)> _19,
+                             TemplateWithIndexer<const char*> _20, std::string s);
 
 void hasIgnoredParam(DependentValueFields<IndependentFields<Ignored>> ii);
 
@@ -750,6 +751,7 @@ template class DLL_API TemplateWithIndexer<UsedInTemplatedIndexer>;
 template class DLL_API TemplateWithIndexer<T1>;
 template class DLL_API TemplateWithIndexer<T2*>;
 template class DLL_API TemplateWithIndexer<float>;
+template class DLL_API TemplateWithIndexer<const char*>;
 template class DLL_API TemplateDerivedFromRegularDynamic<RegularDynamic>;
 template class DLL_API HasCtorWithMappedToEnum<TestFlag>;