read-only functions can not call trait functions even if the implementation uses a read-only function

The following code

(define-read-only (symbol)
  (contract-call? 'ST3J2GVMMM2R07ZFBJDWTYEYAR8FZH5WKDTFJ9AHA.swapr symbol 'ST3J2GVMMM2R07ZFBJDWTYEYAR8FZH5WKDTFJ9AHA.plaid-token 'ST3J2GVMMM2R07ZFBJDWTYEYAR8FZH5WKDTFJ9AHA.stx-token)
)

generates an error expecting read-only statements, detected a writing operation. (i.e. WriteAttemptedInReadOnly) when deploying, even if contract-call? is calling an other define-read-only function.

This should be allowed.

Fix may be related to what is needed for https://github.com/blockstack/stacks-blockchain/issues/1641, and the 2 issues prevent using the RPC read-only call to call any function using contract-call (if you make the function define public then #1641 prevents you as well.