若要将变量强制转换为更宽的类型，请为其创建一个新变量：

interface Foo {
  a: number;
  b: string;
}
interface Bar {
  a: number;
}

const foo: Foo = { a: 1, b: '2' }
const notFoo = { a: 'string' }

// casting foo to `Bar` type, with assignability check
const bar: Bar = foo;

const notBar: Bar = notFoo;
//    ~~~~~~
// Type '{ a: string; }' is not assignable to type 'Bar'.
//   Types of property 'a' are incompatible.
//     Type 'string' is not assignable to type 'number'.(2322)

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