“Elaboration” is the process of identifying all the predicates that
are implied by a source predicate. Currently, this basically means
walking the “supertraits” and other similar assumptions. For example,
if we know that
T: Ord, the elaborator would deduce that
holds as well. Similarly, if we have
trait Foo: 'static, and we know that
T: Foo, then we know that
A filter around an iterator of predicates that makes it yield up
just trait references.
“Trait alias expansion” is the process of expanding a sequence of trait
references into another sequence by transitively following all trait
aliases. e.g. If you have bounds like
Foo + Send, a trait alias
trait Foo = Bar + Sync;, and another trait alias
trait Bar = Read + Write, then the bounds would expand to
Read + Write + Sync + Send.
Expansion is done via a DFS (depth-first search), and the
is used to avoid cycles.
Stores information about the expansion of a trait via a path of zero or more trait aliases.