static char* numberToString (char* t, const int64 n) noexcept
Doesn’t correctly handle the case where n = std::numeric_limits ::min().
A unit test would have discovered this. Here’s part my unit test for my version of lexicalCast which calls the String constructor for int64 as needed:
String s;
s << "numeric_limits <" << typeid (IntType).name () << ">";
beginTestCase (s);
testInteger (std::numeric_limits <IntType>::min ());
testInteger (std::numeric_limits <IntType>::max ());