Question

在VS2015中：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TypeInference
{
    public interface IResolvable<T>
    {
        T Resolve();
    }

    public class Trivial<T> : IResolvable<T>
    {
        private T it;
        public T Resolve() { return it; }

        public Trivial(T the) { it = the; }
    }

    public class TrivialText : Trivial<string>
    {
        public TrivialText(string s) : base(s) { }
    }

    class Program
    {
        static string f(IResolvable<string> s)
        {
            return s.Resolve();
        }

        static void Main(string[] args)
        {
            string s = "yet another string";

            // error CS0305: Using the generic type 'Trivial<T>' requires 1 type arguments
            Console.WriteLine(f(new Trivial("this is a string, right?")));
            Console.WriteLine(f(new Trivial(s)));
            // ok
            Console.WriteLine(f(new Trivial<string>("this is a string, right?")));
            // OK
            Console.WriteLine(f(new TrivialText("this is a string, right?")));
        }
    }
}

这里的类型推断似乎应该是显而易见的。前两行显然是一个字符串，但两种形式都坚持我声明了type参数。这似乎与这里所作的陈述相矛盾：

https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/generics/generic-methods

您也可以省略type参数，编译器会推断它。以下对Swap的调用等同于之前的调用

我做错了吗？

TIA

为什么C＃不能推断出这种类型？

0 个答案: