"Error calling module function" with gql tagged template literals

[darkbasic]

https://github.com/darkbasic/nativescript-repro1/blob/master/app/item/item.service.ts

const taggedTemplateLiteralDoesNotWorkHere = gql`
  query GetChats($amount: Int) {
    chats {
      id
      messages(amount: $amount) {
        id
      }
    }
  }
`;

gql tagged template literals don't work in Nativescript, unless you put them inside a class:

@Injectable()
export class ItemService {
    theSameTaggedTemplateLiteralWorksHere = gql`
      query GetChats($amount: Int) {
        chats {
          id
          messages(amount: $amount) {
            id
          }
        }
      }
    `;
}

If I use gql as a function instead of a tagged template literal it works fine everywhere:

const callingItAsFunctionWorksFine = gql(`
  query GetChats($amount: Int) {
    chats {
      id
      messages(amount: $amount) {
        id
      }
    }
  }
`);

Full Error: http://paste.ubuntu.com/p/SMKyCvGkdW/

I thought it could have been an issue with Typescript's cache (https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-6.html), but I get the same issue with Typescript 2.6, 2.6 and 2.7.

[darkbasic]

"importHelpers": true, in tsconfig.json is among the things required in order to fix this error. I'm not 100% sure this is the only tweak needed because I did try it initially and it didn't work. I'll update this comment later.