GenericMethodHelper
GenericMethodHelper is able to deduce the Type arguments for
a generic method from the actual arguments provided.
using System;
using System.Reflection;
namespace NUnit.Framework.Internal
{
public class GenericMethodHelper
{
private static class ConflictingTypesMarkerClass
{
}
private static readonly Type ConflictingTypesMarker = typeof(ConflictingTypesMarkerClass);
private MethodInfo Method { get; }
private Type[] TypeParms { get; }
private Type[] TypeArgs { get; }
private Type[] ParmTypes { get; }
public GenericMethodHelper(MethodInfo method)
{
Guard.ArgumentValid(method.IsGenericMethod, "Specified method must be generic", "method");
Method = method;
TypeParms = Method.GetGenericArguments();
TypeArgs = new Type[TypeParms.Length];
ParameterInfo[] parameters = Method.GetParameters();
ParmTypes = new Type[parameters.Length];
for (int i = 0; i < parameters.Length; i++) {
ParmTypes[i] = parameters[i].ParameterType;
}
}
public bool TryGetTypeArguments(object[] argList, out Type[] typeArguments)
{
Guard.ArgumentValid(argList.Length == ParmTypes.Length, "Supplied arguments do not match required method parameters", "argList");
for (int i = 0; i < ParmTypes.Length; i++) {
object obj = argList[i];
if (obj != null) {
Type type = obj.GetType();
TryApplyArgType(ParmTypes[i], type);
}
}
Type[] typeArgs = TypeArgs;
foreach (Type left in typeArgs) {
if (left == (Type)null || left == ConflictingTypesMarker) {
typeArguments = null;
return false;
}
}
typeArguments = TypeArgs;
return true;
}
private void TryApplyArgType(Type parmType, Type argType)
{
if (parmType.IsGenericParameter)
ApplyArgType(parmType, argType);
else if (parmType.GetTypeInfo().ContainsGenericParameters) {
Type[] genericArguments = parmType.GetGenericArguments();
if (argType.HasElementType)
ApplyArgType(genericArguments[0], argType.GetElementType());
else if (argType.GetTypeInfo().IsGenericType && IsAssignableToGenericType(argType, parmType)) {
Type[] genericArguments2 = argType.GetGenericArguments();
if (genericArguments2.Length == genericArguments.Length) {
for (int i = 0; i < genericArguments.Length; i++) {
TryApplyArgType(genericArguments[i], genericArguments2[i]);
}
}
}
}
}
private void ApplyArgType(Type parmType, Type argType)
{
int genericParameterPosition = parmType.GenericParameterPosition;
if (!TypeHelper.TryGetBestCommonType(TypeArgs[genericParameterPosition], argType, out TypeArgs[genericParameterPosition]))
TypeArgs[genericParameterPosition] = ConflictingTypesMarker;
}
private bool IsAssignableToGenericType(Type givenType, Type genericType)
{
Type[] interfaces = givenType.GetInterfaces();
foreach (Type type in interfaces) {
if (type.GetTypeInfo().IsGenericType) {
Type genericTypeDefinition = type.GetGenericTypeDefinition();
if (genericTypeDefinition.Name == genericType.Name && genericTypeDefinition.Namespace == genericType.Namespace)
return true;
}
}
if (givenType.GetTypeInfo().IsGenericType) {
Type genericTypeDefinition2 = givenType.GetGenericTypeDefinition();
if (genericTypeDefinition2.Name == genericType.Name && genericTypeDefinition2.Namespace == genericType.Namespace)
return true;
}
Type baseType = givenType.GetTypeInfo().BaseType;
if (baseType == (Type)null)
return false;
return IsAssignableToGenericType(baseType, genericType);
}
}
}