page 43, Dart Fundamentals for this description " Some programming languages aren’t as strict and will perform conversions like this
silently. Experience shows this kind of silent, implicit conversion is a frequent source of
software bugs and often hurts code performance. Dart disallows you from assigning a
value of one type to another and avoids these issues."
dart has implicit widening type conversion like java as we can write int value for double variable
double d = 2; // it will comple.