Implicit conversion in array initializer list

Question

Why implicit conversion from const char* to std::string does not work in the latter case? Link a reference to C++ standard if possible, please.

Variant 1:

struct Foo {
    Foo(const char* a) {}
};

int main() {
   // works well for a "const char*" accepting constructor
   Foo* foo = new Foo[1] { "a" };
}

Variant 2:

struct Foo {
    Foo(std::string a) {}
};

int main() {
   // could not convert from "const char*" to "Foo"
   Foo* foo = new Foo[1] { "a" };
}

Answer 1

At most one user-defined conversion is allowed in a user-defined conversion sequence (12.3p4).

You can use an extra level of braces to make it work:

   Foo* foo = new Foo[1] { {"a"} };

Note that because of a bug in clang it requires Foo to have a default constructor Foo::Foo() even though it will not actually be called.