From the github issue mentioned by @Ahmed I. Elsayed, the following is relevant answer provided by @LRN
Reference
The real question, if you are going for consistency, is why int is not
Int. Dart generally capitalize types, so the exception here is not
String, it is int, double and bool (and void, but that wasn't
originally a real type).
So if you want consistency, we should make int be Int. Or maybe it
should even be Integer, because we also discourage abbreviations.
In Java, int is lower case and Integer is capitalized because the
former is a primitive type and the latter is an object type. Dart does
not have that distinction, our int is an object type, so we don't
actually have any consistency-based reason for making int short and
lower-case.
Or maybe there is one reason: int, double and bool instances are
automatically canonicalized. You cannot have two int instances with
the same value without them being identical. That's the one property
that Dart has taken from Java/C#/JavaScript primitive types, and it
does not apply to strings (like it doesn't in Java and C# either).
The real reason Dart has those exceptions (int, double and bool) is
because of trade-offs between usability, user expectation and
consistency. Dart was designed as a pragmatic language. It values
consistency, but not at any price. The familiarity/user-expectation
goal was generally influenced by Java, JavaScript and C#, and it was
considered better usability to make those types short, recognizable
and easy to write.
Making String be string was not a trade-off that seemed worth it. It
would probably have worked perfectly well if we had used string
instead, but we didn't. We are not going to change that now.
(If we get generalized type aliases, you can probably define your own
typedef string = String;. I implore you not to, because it would not
improve the readability of your code. Historically, the reason Java
did not have a C-like #define functionality was explicitly because
they did not want people writing in a myriad of private dialects that
other people couldn't read).
