private static MethodBuilder GetPropertyGetMethod(TypeBuilder proxyTypeBuilder, Type targetType, MemberInfo proxyMember, PropertyInfo targetProperty, FieldInfo instanceField)
{
var proxyMemberName = proxyMember.Name;
var proxyMemberReturnType = typeof(object);
var proxyParameterTypes = Type.EmptyTypes;
var targetParametersTypes = GetPropertyGetParametersTypes(proxyTypeBuilder, targetProperty, true).ToArray();
if (proxyMember is PropertyInfo proxyProperty)
{
proxyMemberReturnType = proxyProperty.PropertyType;
proxyParameterTypes = GetPropertyGetParametersTypes(proxyTypeBuilder, proxyProperty, true).ToArray();
if (proxyParameterTypes.Length != targetParametersTypes.Length)
{
DuckTypePropertyArgumentsLengthException.Throw(proxyProperty);
}
}
else if (proxyMember is FieldInfo proxyField)
{
proxyMemberReturnType = proxyField.FieldType;
proxyParameterTypes = Type.EmptyTypes;
if (proxyParameterTypes.Length != targetParametersTypes.Length)
{
DuckTypePropertyArgumentsLengthException.Throw(targetProperty);
}
}
var proxyMethod = proxyTypeBuilder.DefineMethod(
"get_" + proxyMemberName,
MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.Final | MethodAttributes.HideBySig | MethodAttributes.Virtual,
proxyMemberReturnType,
proxyParameterTypes);
var il = new LazyILGenerator(proxyMethod.GetILGenerator());
var targetMethod = targetProperty.GetMethod;
var returnType = targetProperty.PropertyType;
// Load the instance if needed
if (!targetMethod.IsStatic)
{
il.Emit(OpCodes.Ldarg_0);
il.Emit(instanceField.FieldType.IsValueType ? OpCodes.Ldflda : OpCodes.Ldfld, instanceField);
}
// Load the indexer keys to the stack
for (var pIndex = 0; pIndex < proxyParameterTypes.Length; pIndex++)
{
var proxyParamType = proxyParameterTypes[pIndex];
var targetParamType = targetParametersTypes[pIndex];
// Check if the type can be converted of if we need to enable duck chaining
if (NeedsDuckChaining(targetParamType, proxyParamType))
{
// Load the argument and cast it as Duck type
il.WriteLoadArgument(pIndex, false);
il.Emit(OpCodes.Castclass, typeof(IDuckType));
// Call IDuckType.Instance property to get the actual value
il.EmitCall(OpCodes.Callvirt, DuckTypeInstancePropertyInfo.GetMethod, null);
targetParamType = typeof(object);
}
else
{
il.WriteLoadArgument(pIndex, false);
}
// If the target parameter type is public or if it's by ref we have to actually use the original target type.
targetParamType = UseDirectAccessTo(proxyTypeBuilder, targetParamType) || targetParamType.IsByRef ? targetParamType : typeof(object);
il.WriteTypeConversion(proxyParamType, targetParamType);
targetParametersTypes[pIndex] = targetParamType;
}
// Call the getter method
if (UseDirectAccessTo(proxyTypeBuilder, targetType))
{
// If the instance is public we can emit directly without any dynamic method
// Method call
if (targetMethod.IsPublic)
{
// We can emit a normal call if we have a public instance with a public property method.
il.EmitCall(targetMethod.IsStatic || instanceField.FieldType.IsValueType ? OpCodes.Call : OpCodes.Callvirt, targetMethod, null);
}
else
{
// In case we have a public instance and a non public property method we can use [Calli] with the function pointer
il.WriteMethodCalli(targetMethod);
}
}
else
{
// If the instance is not public we need to create a Dynamic method to overpass the visibility checks
// we can't access non public types so we have to cast to object type (in the instance object and the return type).
var dynMethodName = $"_getNonPublicProperty_{targetProperty.DeclaringType.Name}_{targetProperty.Name}";
returnType = UseDirectAccessTo(proxyTypeBuilder, targetProperty.PropertyType) ? targetProperty.PropertyType : typeof(object);
// We create the dynamic method
var targetParameters = GetPropertyGetParametersTypes(proxyTypeBuilder, targetProperty, false, !targetMethod.IsStatic).ToArray();
var dynParameters = targetMethod.IsStatic ? targetParametersTypes : (new[] { typeof(object) }).Concat(targetParametersTypes).ToArray();
var dynMethod = new DynamicMethod(dynMethodName, returnType, dynParameters, proxyTypeBuilder.Module, true);
// Emit the dynamic method body
var dynIL = new LazyILGenerator(dynMethod.GetILGenerator());
if (!targetMethod.IsStatic)
{
dynIL.LoadInstanceArgument(typeof(object), targetProperty.DeclaringType);
}
for (var idx = targetMethod.IsStatic ? 0 : 1; idx < dynParameters.Length; idx++)
{
dynIL.WriteLoadArgument(idx, true);
dynIL.WriteTypeConversion(dynParameters[idx], targetParameters[idx]);
}
dynIL.EmitCall(targetMethod.IsStatic || instanceField.FieldType.IsValueType ? OpCodes.Call : OpCodes.Callvirt, targetMethod, null);
dynIL.WriteTypeConversion(targetProperty.PropertyType, returnType);
dynIL.Emit(OpCodes.Ret);
dynIL.Flush();
// Emit the call to the dynamic method
il.WriteDynamicMethodCall(dynMethod, proxyTypeBuilder);
}
// Handle the return value
// Check if the type can be converted or if we need to enable duck chaining
if (NeedsDuckChaining(targetProperty.PropertyType, proxyMemberReturnType))
{
if (UseDirectAccessTo(proxyTypeBuilder, targetProperty.PropertyType) && targetProperty.PropertyType.IsValueType)
{
il.Emit(OpCodes.Box, targetProperty.PropertyType);
}
// We call DuckType.CreateCache<>.Create()
var getProxyMethodInfo = typeof(CreateCache <>)
.MakeGenericType(proxyMemberReturnType).GetMethod("Create");
il.Emit(OpCodes.Call, getProxyMethodInfo);
}
else if (returnType != proxyMemberReturnType)
{
// If the type is not the expected type we try a conversion.
il.WriteTypeConversion(returnType, proxyMemberReturnType);
}
il.Emit(OpCodes.Ret);
il.Flush();
_methodBuilderGetToken.Invoke(proxyMethod, null);
return(proxyMethod);
}