Tools

yarn

无论是否 —force，yarn 在进行依赖安装（install）时都不会进行原有依赖的删除，于是就会出现一些神奇的问题。
node_modules 中会存在一些不需要的包。
可能是 babel 具有某种批量读取的效果？抑或是引用出错，会导致错误的加载顺序，或包的运行问题。

When an indexed access T[K] occurs on the source side of a type relationship, it resolves to a union type of the properties selected by T[K], but when it occurs on the target side of a type relationship, it now resolves to an intersection type of the properties selected by T[K]. Previously, the target side would resolve to a union type as well, which is unsound.
Given a type variable T with a constraint C, when an indexed access T[K] occurs on the target side of a type relationship, index signatures in C are now ignored. This is because a type argument for T isn’t actually required to have an index signature, it is just required to have properties with matching types.
A type { [key: string]: number } is no longer related to a mapped type { [P in K]: number }, where K is a type variable. This is consistent with a string index signature in the source not matching actual properties in the target.
Constraints of indexed access types are now more thoroughly explored. For example, given type variables T and K extends 'a' | 'b', the types { a: T, b: T }[K] and T are now considered related where previously they weren’t.