Generate valid C# for constructors taking const&

Fixes https://github.com/mono/CppSharp/issues/1119.

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

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -2640,10 +2640,11 @@ namespace CppSharp.Generators.CSharp
         {
             if (method.SynthKind == FunctionSynthKind.ComplementOperator)
             {
+                Parameter parameter = method.Parameters[0];
                 if (method.Kind == CXXMethodKind.Conversion)
                 {
                     // To avoid ambiguity when having the multiple inheritance pass enabled
-                    var paramType = method.Parameters[0].Type.SkipPointerRefs().Desugar();
+                    var paramType = parameter.Type.SkipPointerRefs().Desugar();
                     paramType = (paramType.GetPointee() ?? paramType).Desugar();
                     Class paramClass;
                     Class @interface = null;
@@ -2651,9 +2652,10 @@ namespace CppSharp.Generators.CSharp
                         @interface = paramClass.GetInterface();
 
                     var paramName = string.Format("{0}{1}",
-                        method.Parameters[0].Type.IsPrimitiveTypeConvertibleToRef() ?
+                        !parameter.QualifiedType.IsConstRefToPrimitive() &&
+                        parameter.Type.IsPrimitiveTypeConvertibleToRef() ?
                         "ref *" : string.Empty,
-                        method.Parameters[0].Name);
+                        parameter.Name);
                     var printedType = method.ConversionType.Visit(TypePrinter);
                     if (@interface != null)
                     {
@@ -2667,8 +2669,8 @@ namespace CppSharp.Generators.CSharp
                 {
                     var @operator = Operators.GetOperatorOverloadPair(method.OperatorKind);
 
-                    WriteLine("return !({0} {1} {2});", method.Parameters[0].Name,
-                              @operator, method.Parameters[1].Name);
+                    WriteLine("return !({0} {1} {2});", parameter.Name,
+                        @operator, method.Parameters[1].Name);
                 }
                 return;
             }

tests/Common/Common.Tests.cs

@@ -20,8 +20,9 @@ public class CommonTests : GeneratorTestFixture
         }
         Foo.NestedAbstract a;
         Foo.RenamedEmptyEnum.EmptyEnum1.GetHashCode();
-        using (var foo = new Foo())
+        using (var foo = new Foo(5))
         {
+            Assert.That(foo.B, Is.EqualTo(5));
             Bar bar = foo;
             Assert.IsTrue(Bar.Item.Item1 == bar);
 

tests/Common/Common.cpp

@@ -54,6 +54,11 @@ Foo::Foo(Private p)
 {
 }
 
+Foo::Foo(const float& f)
+{
+    B = f;
+}
+
 const char* Foo::GetANSI()
 {
     return "ANSI";

tests/Common/Common.h

@@ -85,6 +85,7 @@ public:
 
     Foo();
     Foo(Private p);
+    Foo(const float& f);
     int A;
     float B;
     IgnoredType ignoredType;