It looks really good for a first release. The focus on tooling is IMO the most refreshing thing about the project; the playground is great!
I haven't dug much into it yet, but there are a couple of annoyances that i noticed in the playground that i wish will be corrected/alleviated somehow:
- The language is not expression-oriented. Once i got used to the "everything is an expression" mindset in languages like CoffeeScript or Ruby (or every functional language that i can think of) it feels quite tedious to "go back" and remember that, no, now the "if" is not an expression any more, you can't return it, or pass it to a function, or assign it to something. You can use the special syntax of the "?:" operator for an if-expression, but there is no equivalent for "switch", or "try", or "for".
- The type system doesn't seem to support parametric polymorphism. For example, the type of string[]::map is ((string, number, string[]) => any, any) => any[] instead of ((string, number, string[]) => T, any) => T[]. So the value ["hello", "world"].map((s) => s + '!') is of type any[] instead of string[], which would be preferable IMO.
TypeScript will eventually support generics, as per the spec [1]:
NOTE: TypeScript currently doesn’t support Generics, but we expect to include them in the
final language. Since TypeScript’s static type system has no run-time manifestation, Generics
will be based on “type erasure” and intended purely as a conduit for expressing parametric type
relationships in interfaces, classes, and function signatures.
I haven't dug much into it yet, but there are a couple of annoyances that i noticed in the playground that i wish will be corrected/alleviated somehow:
- The language is not expression-oriented. Once i got used to the "everything is an expression" mindset in languages like CoffeeScript or Ruby (or every functional language that i can think of) it feels quite tedious to "go back" and remember that, no, now the "if" is not an expression any more, you can't return it, or pass it to a function, or assign it to something. You can use the special syntax of the "?:" operator for an if-expression, but there is no equivalent for "switch", or "try", or "for".
- The type system doesn't seem to support parametric polymorphism. For example, the type of string[]::map is ((string, number, string[]) => any, any) => any[] instead of ((string, number, string[]) => T, any) => T[]. So the value ["hello", "world"].map((s) => s + '!') is of type any[] instead of string[], which would be preferable IMO.