Merge broken after upgrade to 5.4.2 #1342

Bug description

The change comes from this PR: #1327

Before, you could do:

type C = Merge<A, B>;
declare let a: A;
declare let b: B;
let c: C = { ...a, ...b }

After the update, this fails with Type 'A & B' is not assignable to type 'Merge<...>.
Couldn't reproduce it in the playground.

Repro

https://www.typescriptlang.org/play/?#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