akaptur

StateTypes = Literal["loading", "loaded", "error"]

akaptur

class State(enum.Enum):
    loading = "loading"
    loaded = "loaded"
    error = "error"

akaptur

type Account = {
  name: string,
  balance: string,
}
function makeAccount({
  name = "foo", 
  balance = "10.05"
}: Partial<Account> = {}): Account {
  return {name, balance}
}

akaptur

	Structural typing	Nominative typing
TypeScript	default behavior	Use tagged unions
Python with mypy	Use protocols	default behavior

akaptur

const val = {value: "hi", kind: "a" as const, image: "a gzipped photo of a cat"}
my_func(val); // no error

akaptur

type A = {
  value: string;
  kind: "a"; // here's the tag
};
type B = {
  value: string;
  kind: "b";
};
function my_func(a: A): string {
  return a.value;

akaptur

from typing import Protocol

class MyProto(Protocol):
   value: str

@dataclass
class A:
   value: str

@dataclass

akaptur

type A = {
  value: string;
}
function my_func(a: A): string {
  return a.value;
}
my_func({value: "hi", image: "a gzipped picture of a cat"}); // no error

akaptur

class A {
  value: string;
  constructor(val: string) {
    this.value = val;
  }
};
class B {
  value: string;
  constructor(val: string) {
    this.value = val;

akaptur

type A = {
  value: string;
};
type B = {
  value: string;
};
function my_func(a: A): string {
  return a.value;
}
my_func({value: "hi"}); // no error here!