Readonly prevents indexer assignment in class constructor

[axefrog]

TypeScript Version: 2.4.2

Code

class Environment {
  readonly [key: string]: Domain;

  constructor (domains: Domain[]) {
    for (let domain of domains) {
      this[domain.name] = domain;
    }
  }
}

Expected behavior:

I'm assigning the values in the constructor, so I would assume that the readonly modifier would not take effect yet.

Actual behavior:

Index signature in type 'Environment' only permits reading.
(property) Domain.name: string

Is this a bug or does TypeScript disallow assignment to readonly indexers due to implementation difficulties?

[mhegazy]

duplicate of #6781

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.