overload-resolution

Consider the following simple (to the extent that template questions ever are) example: #include <iostream> template <typename T> struct identity; template <> struct identity<int> { using type = int; }; template<typename T> void bar(T, T ) { std::cout << "a\n"; } template<typename T> void bar(T, typename identity<T>::type) { std::cout << "b\n"; } int main () { bar(0, 0); } Both clang and gcc print "a" there. According to the rules in [temp.deduct.partial] and [temp.func.order], to determine partial ordering, we need to synthesize some unique types. So we have two attempts at deduction: +---+--

Consider the following code (it's a little long, but hopefully you can follow): class A { } class B : A { } class C { public virtual void Foo(B b) { Console.WriteLine("base.Foo(B)"); } } class D: C { public override void Foo(B b) { Console.WriteLine("Foo(B)"); } public void Foo(A a) { Console.WriteLine("Foo(A)"); } } class Program { public static void Main() { B b = new B(); D d = new D (); d.Foo(b); } } If you think the output of this program is "Foo(B)" then you'd be in the same boat as me: completely wrong! In fact, it outputs "Foo(A)" If I remove the virtual method from the C class, then

The following call to the overloaded Enumerable.Select method: var itemOnlyOneTuples = "test".Select<char, Tuple<char>>(Tuple.Create); fails with an ambiguity error (namespaces removed for clarity): The call is ambiguous between the following methods or properties: 'Enumerable.Select<char,Tuple<char>> (IEnumerable<char>,Func<char,Tuple<char>>)' and 'Enumerable.Select<char,Tuple<char>> (IEnumerable<char>, Func<char,int,Tuple<char>>)' I can certainly understand why not specifying the type-arguments explicitly would result in an ambiguity (both the overloads would apply), but I don't see one