Off the top of my head, no access modifiers (so private variables, for example, are prefixed with `_`, by convention, not enforced by the compiler), no pattern matching (and obviously no exhaustive matching), no record types, no sum types, no json (de)serialization (requires 3rd party libary code gen, wow), mutability everywhere, everything is a statement (i.e. no implicit `return`, AKA everything is an expression), required semi-colons (which they'd like to get rid of but can't due to questionable design decisions made long ago -- for the gory details see here[1]).

If you like Java 8 and earlier you'll probably feel at home with Dart.

Obviously I'm biased, but I find Dart to be one of the most unpleasant languages I've had the misfortune of being exposed to; this despite Flutter and its instantaneous hot code reloading being quite amazing -- a bizarre mix of promise and despair.

[1] https://github.com/dart-lang/language/blob/master/resources/...