In my opinion, if you're able to build a JSON (de)serialization and pretty printing library in tsuki, without running into major bugs or missing features, that's the point at which version 0.1.0 should be released.
Such a library would test compiler support for the most critical components of the language:
Basic control flow structures
Functions
Objects - you need to store the lexer state somehow, while the parser is chewing away at the tokens.
Unions - speaking of tokens, you need to represent those too, somehow.
Traits - the parser needs to notify the consumer of all the values it encounters along the way.
Atoms - we need a way of discriminating error kinds inside the library.
FFI - the easiest way of printing things to stdout (or a file) is by using libc, so the standard library could initially use that to accelerate development. For that we need FFI with C.
Standard library
Support for primitive data types.
String manipulation.
Advanced functionality for primitive data types, such as parsing numbers.
Generic data structures such as Seq[T] and Table[K, V].
In my opinion, if you're able to build a JSON (de)serialization and pretty printing library in tsuki, without running into major bugs or missing features, that's the point at which version 0.1.0 should be released.
Such a library would test compiler support for the most critical components of the language:
Seq[T]andTable[K, V].