Generate valid C# when std::string is only used for non-private fields

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

src/Generator/Passes/TrimSpecializationsPass.cs

@@ -85,9 +85,7 @@ namespace CppSharp.Passes
                 return true;
             }
 
-            TypeMap typeMap;
-            if (!Context.TypeMaps.FindTypeMap(field.Type, out typeMap) &&
-                !ASTUtils.CheckTypeForSpecialization(field.Type,
+            if (!ASTUtils.CheckTypeForSpecialization(field.Type,
                     field, AddSpecialization, Context.TypeMaps))
                 CheckForInternalSpecialization(field, field.Type);
 

tests/VTables/VTables.Tests.cs

@@ -78,4 +78,15 @@ public class VTablesTests : GeneratorTestFixture
         var retBase = new ManagedDerivedClassVirtualRetBase();
         TestVirtualFunction(retBase, 10);
     }
+
+    [Test]
+    public void TestStdStringInField()
+    {
+        using (var foo = new Foo())
+        {
+            Assert.That(foo.S, Is.Empty);
+            foo.S = "test";
+            Assert.That(foo.S, Is.EqualTo("test"));
+        }
+    }
 }

tests/VTables/VTables.h

@@ -1,4 +1,5 @@
 #include "../Tests.h"
+#include <string>
 
 class DLL_API Foo
 {
@@ -15,6 +16,7 @@ public:
     virtual int append();
     virtual int append(int a);
     int callVirtualWithParameter(int a);
+    std::string s;
 };
 
 DLL_API int FooCallFoo(Foo* foo);