Object spreading a Record<string, any> gives wrong type

[golopot]

TypeScript Version: 3.4.0-dev.20190322

Search Terms:
object spread, Record, index signature

Code

const fn = (a: Record<string, any>) => {
  const obj = { p: 1, ...a };

  obj.foo; // ts-error: Property 'foo' does not exist on type '{ p: number; }'
};

const fn2 = (a: { [_: string]: any }) => {
  const obj = { p: 1, ...a };

  obj.foo; // ts-error: Property 'foo' does not exist on type '{ p: number; }'
};

Expected behavior:

obj has type {p: number} & Record<string, any>.

This matches how typescript handles Object.assign.

Actual behavior:

Type of object-spreaded thing is ignored.

Playground Link:

link

Related Issues:

[ajafff]

This is a duplicate of #27273

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.