Incomplete type not allowed when using new[] keyword

Question

This code gives errors

incomplete type is not allowed

too many initializer values

string *ReturnTwoStringsInArray()
{
   return new string[]{"return1", "return2"};
}

This one works:

string *ReturnTwoStringsInArray()
{
   return new string[2]{"return1", "return2"};
}

And so does this one:

string arr[]{"return1","return"};

Shouldn't we be able to call new with no parameters in [] if the compiler can determine the needed size from the initializer list?

Answer 1

In C++ compiler support we can see that the defect report P1009R2:Array size deduction in new-expressions has not been adopted by all compiler vendors yet.

P1009R2 says: "The effect of the wording changes should be applied in implementations of all previous versions of C++ where they apply."

clang++ supports it from version 9 in C++11 mode and later.