It's not type-safe of course. Each function taking a Context has an implicit interface (the required key-value pairs that the caller must provide in the context) and failing to provide an expected binding will likely result in a runtime error.

This is why dependency injection frameworks like Guice and Dagger went with a different approach: they provide environment values to a class's constructor using reflection. Then the framework can do type checking at startup (for Guice) or compile time (for Dagger).

However, that has different costs: it requires a class per component instead of a function per component, and the framework is more complicated. This is an engineering tradeoff and apparently the developers of Context decided on simplicity.