CartTotalRepository cannot handle extension attributes in quote addresses

[ekuusela]

Extension attributes in quote billing or shipping addresses cause Magento\Quote\Model\Cart\CartTotalRepository::get to throw this error:

"PHP message: PHP Fatal error:  Uncaught TypeError: Argument 1 passed to Magento\Quote\Model\Cart\Totals::setExtensionAttributes() must be an instance of Magento\Quote\Api\Data\TotalsExtensionInterface, instance of Magento\Quote\Api\Data\AddressExtension given

This happens for example when /carts/mine/payment-information is requested while modifying billing address during checkout.

Here's a similar issue with adding extension attributes to CartItemInterface: #3640

Preconditions

1. Magento 2.1.3 to 2.1.6
2. Extension attributes defined for quote shipping or billing addresses

Steps to reproduce

Assuming extension attributes for the quote billing address have been defined

1. login as a user who has at least two addresses in his address book
2. add a virtual product to card and proceed to checkout
3. choose or change the billing address, click update

Expected result

1. no errors, address is changed

Actual result

1. error is thrown and the checkout loader gets stuck

[magento-team]

Internal ticket to track issue progress: MAGETWO-69223

[magento-engcom-team]

Hi @ekuusela
Thank you for reporting and fixing the issue with the PR.
As it is already delivered into 2.1.8 we are closing this issue.
Thank you for collaboration.