Types

From the Prelude step and moving on, there are ubiquitous types that are primarily involved with tracking the access path of a API surface.

Name

A simple DU that always persists the source material string. This allows us to reference the source material string in emissions, even after modifications.

We can access the source value via the property .ValueOrSource, and can access the modified value (or the source if it was unmodified) via .ValueOrModified.

Path

Recursive types that create a chain of parent/child relationships to signify the path of access. These are compiled into a wrapper DU named PathKey which provides a unified interface for using the types.

When a PathKey is provided to the binding tracePathOfEntry, it will return the list of Name's to arrive at the destination. This is how we derive the names of generated string enums et al.

Cache

Since we map process specific types into wrapper modules such as Main, a to the type by name will not work if it is originating from another module.

Therefore, we cache the original name of types against their generated PathKey's, and refer to this when we arrive at a type value that is a reference to an unknown object.

The cache is searched for that name, and the path is returned if successful. On failure, we typically just emit the string directly. If the source is invalid because no type exists by that name, then we must determine where the dependency lies, and either bind it ourselves, or include the dependency from another Fable binding.