Generic type inference doesnt take polymorphism into account

Hi here is my example let's say

class A { }
class B : A { }

void test<T>(T clazz)
{
     Console.WriteLine("clazz type = {0} T type = {1}",
                 clazz.GetType().Name,
                 typeof(T).Name);
}

static void Main(string[] args)
{         
    A b = new B(); 
    test(b);
    Console.ReadLine();
}

The result is clazz= B T= A ????? why inference generic type doesn't take into account polymorphism ?

Jon Skeet
people
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The result is clazz= B T= A ????? why inference generic type doesn't take into account polymorphism ?

Type inference is performed at compile time. The compile time type of the variable b is A, so the compiler infers that you meant:

test<A>(b);

The fact that the value of b at execution time is B is irrelevant, because that's too late for type inference.

As of C# 4 you can defer the type inference until execution time using dynamic though:

dynamic b = new B();
test(b);

people

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