TypeScript 错误“‘删除’操作符的操作数必须是可选的"背后的逻辑是什么?

问题描述

这是打字稿代码中出现的新错误.

This is the new error that is coming in typescript code.

我无法理解其背后的逻辑
文档

I am not able to realize the logic behind it
Documentation

/*When using the delete operator in strictNullChecks, 
the operand must now be any, unknown, never, or be optional 
(in that it contains undefined in the type). Otherwise, use of the delete operator is an error.*/

interface Thing {
  prop: string;
}

function f(x: Thing) {
  delete x.prop; // throws error = The operand of a 'delete' operator must be optional.
}

推荐答案

据我所知，逻辑如下:

Interface Thing 是一个契约，要求将(非空，非未定义)prop 作为 string.

Interface Thing is a contract asking to have a (non-null, non-undefined) prop as a string.

如果移除财产，则合同不再执行.

If one removes the property, then the contract is not implemented anymore.

如果您希望它在删除后仍然有效，只需使用 ? 将其声明为可选:prop?: string

If you want it still valid when removed, just declare it as optional with a ?: prop?: string

我实际上很惊讶这并没有在早期版本的 TypeScript 中导致错误.

I'm actually surprised that this was not causing error in earlier versions of TypeScript.

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