ButtonTitleToTip is an object with 2 keys that are literals. props.route.name is just a string so flow doesn't know if we can safely do this.

We can but a line lower you have a check if tipType is defined anyway.

Do you mean there were + signs before and now there aren't and maybe we changed the mutability?
The props are now arguments in component function so we can't control mutability here. The docs don't say anything about mutability here . And there is no js definition of component function so we can't check.

We can't put void here because of ComponentType definition:

declare export type ComponentType<-P: {...}> = component(...P)

P can't be void because it has to extend {...}.
And what is the meaning of void here? Component with no props? I can put { ... } here?