“Collection” is the process of determining the type and other external details of each item in Rust. Collection is specifically concerned with inter-procedural things – for example, for a function definition, collection will figure out the type and signature of the function, but it will not visit the body of the function in any way, nor examine type annotations on local variables (that’s the job of type checking).
Collecting is ultimately defined by a bundle of queries that
inquire after various facts about the items in the crate (e.g.,
predicates_of, etc). See the
for the full set.
At present, however, we do run collection across all items in the crate as a kind of pass. This should eventually be factored away.
- Resolution of early vs late bound lifetimes.
- type_of 🔒
- Context specific to some particular item. This is what implements
- adt_def 🔒
- Returns the early-bound lifetimes declared in this generics listing. For anything other than fns/methods, this is just all the lifetimes that are declared. For fns or methods, we have to screen out those that do not appear in any where-clauses etc using
- fn_sig 🔒
- Synthesize a new lifetime name that doesn’t clash with any of the lifetimes already present.
tyis a type with
_placeholders that can be inferred. Used in diagnostics only to use inference to provide suggestions for the appropriate type if possible.
- If there are any placeholder types (
_), emit an error explaining that this is not allowed and suggest adding type parameters in the appropriate place, taking into consideration any and all already existing generic type parameters to avoid suggesting a name that is already in use.
- Returns a list of type predicates for the definition with ID
def_id, including inferred lifetime constraints. This includes all predicates returned by
explicit_predicates_of, plus inferred constraints concerning which regions outlive other regions.