如何将Blob约束到特定类型

每 https://github.com/microsoft/TypeScript/blob/29becf05012bfa7ba20d50b0d16813971e46b8a6/lib/lib.webworker.d.ts#L641-L646 ,我明白了 Blob :

/** A file-like object of immutable, raw data. Blobs represent data that isn't necessarily in a JavaScript-native format. The File interface is based on Blob, inheriting blob functionality and expanding it to support files on the user's system. */
interface Blob {
    readonly size: number;
    readonly type: string;
    slice(start?: number, end?: number, contentType?: string): Blob;
}

我希望将这种类型限制为坚持使用特定类型的Blob type

Mapped Type 和/或 intersection type ,但特别是作为TS的新手,我不清楚映射类型的示例是否正在更改所有属性,以及如何正确约束它。

我本以为我可以这样做:

type HTMLBlob = {
  [P in keyof Blob]?: Blob[P];
} & { type: 'text/html' }

function handleHTMLBlob(blob : HTMLBlob) {
  // ...
}

const blob : HTMLBlob = new Blob(['<b>Test</b>'], { type: 'text/html' });

handleHTMLBlob(blob);

但游乐场报道:

Type 'Blob' is not assignable to type 'HTMLBlob'.
  Type 'Blob' is not assignable to type '{ type: "text/html"; }'.
    Types of property 'type' are incompatible.
      Type 'string' is not assignable to type '"text/html"'.

斑点 (此外 类型 )既然 一旦获得新属性,我希望我的Blob子类型自动继承这些属性。)