Anything with a source location and set of attributes and, optionally, a name. That is, anything that can be documented. This doesn't correspond directly to the AST's concept of an item; it's a strict superset.

This is a more limited form of the standard Struct, different in that it lacks the things most items have (name, id, parameterization). Found only as a variant in an enum.

A representation of a Type suitable for hyperlinking purposes. Ideally one can get the original type out of the AST/ty::ctxt given one of these, if more information is needed. Most importantly it does not preserve mutability or boxes.