Before this commit, Env was an indexed type, this means that one could
write env.anything, and it would accept it as a valid type. This is
actually quite dangerous, because we lose the typing advantages for all
keys that are properly defined.
For example, if a component is defined as:
class MyComponent extends Component<Props> {
...
}
Then Typescript will let it use anything from the environment, even if
it is wrong. So, most properly typed Typescript applications should use
instead a sub environment:
interface MyAppEnv extends Env {
someKey: someValue
}
Then, the component should be defined this way:
class MyComponent extends Component<Props, MyAppEnv> {
...
}
Before this commit, any typos in the environment accesses would not be
noticed by typescript.
Géry Debongnie