attribute named "toString" does not work with associations

[jharting]

What are you doing?

For backwards compatibility reasons we need to continue supporting attributes named "toString" in our app. (I know, I know, what an odd name!). Sequelize used to support this in v3 but there were regressions with v4. These regressions were mostly dealt with in #8719 but recently I run into another problem when associations are involved.

What do you expect to happen?

I expect the value of the attribute named toString to work as any other argument

What is actually happening?

The query yields 0 results

Dialect: mysql
Database version: 10.1.26
Sequelize version: 4.33.4
Tested with master branch: Yes