泛型扩展方法的编译器错误
本文关键字:编译器 错误 方法 扩展 泛型 | 更新日期: 2023-09-27 18:10:15
我正试图编写一个编译器在运行时无法解析的通用扩展方法,尽管visual studio的智能感知确实找到了它。
编译错误是'SampleSolution.OtherGenericClass<SampleSolution.IGenericInterface<SampleSolution.ISimpleInterface>,SampleSolution.ISimpleInterface>' does not contain a definition for 'GenericExtensionMethod' and no extension method 'GenericExtensionMethod' accepting a first argument of type 'SampleSolution.OtherGenericClass<SampleSolution.IGenericInterface<SampleSolution.ISimpleInterface>,SampleSolution.ISimpleInterface>' could be found (are you missing a using directive or an assembly reference?)
下面是一些示例代码,以我能想到的最简单的形式再现了这个问题。我知道我可以在IOtherGenericInterface
中添加GenericExtensionMethod
,但我需要一个扩展方法,因为它需要在IOtherGenericInterface
实现之外。
public interface ISimpleInterface
{
}
public interface IGenericInterface<T>
{
}
public class GenericClass<T> : IGenericInterface<T>
{
}
public interface IOtherGenericInterface<TGenericDerived>
{
}
public class OtherGenericClass<TGenericInterface, TSimpleInterface> :
IOtherGenericInterface<TGenericInterface>
where TGenericInterface : IGenericInterface<TSimpleInterface>
{
}
public static class GenericExtensionMethods
{
public static IOtherGenericInterface<TGenericInterface>
GenericExtensionMethod<TGenericInterface, TSimple>(
this IOtherGenericInterface<TGenericInterface> expect)
where TGenericInterface : IGenericInterface<TSimple>
{
return expect;
}
}
class Program
{
static void Main(string[] args)
{
var exp = new OtherGenericClass<IGenericInterface<ISimpleInterface>,
ISimpleInterface>();
//exp.GenericExtensionMethod(); // This doesn't compile
}
}
它没有足够的信息来明确解析泛型类型参数;你必须使用:
exp.GenericExtensionMethod<IGenericInterface<ISimpleInterface>, ISimpleInterface>();
特别要注意的是,where
约束是在解析之后验证的——它们不参与解析本身——所以在解析期间,它只能推断TGenericInterface
。