Collections and generics¶

Li mirrors Python 3.14 collection typing where possible, compiled to native layouts.

list[T]¶

def sum(xs: list[int]) -> int

Dynamic length; allocation may raises Alloc.

dict[K, V]¶

def lookup(m: dict[str, int], key: str) -> int

Arity and key types are checked statically.

tuple and named tuples¶

type Pair = tuple[a: int, b: float]

Variadic tuples supported in tests (li-tests/collections/).

TypedDict¶

type Config = TypedDict
  host: str
  port: int

enum¶

type Mode = enum
  Off, On, Auto

Generics (PEP 695)¶

def box[T](x: T) -> T
  requires true
  ensures result == x
  decreases 0
=
  return x

Type parameters in square brackets on def and type.

Protocol and Callable¶

Structural protocols (e.g. Sized) and function types for higher-order code.

Tests: li-tests/generics/.

Arrays vs lists¶