Put AvailabilityRange into its own header with very few dependencies so that it
can be included freely in other headers that need to use it as a complete type.
NFC.
This convenience returns an optional `SemanticAvailableAttr` (since in the
future, lookup of the `AvailabilityDomain` can fail). It replaces
`Decl::getDomainForAvailableAttr()`, since most callers will need to form a
`SemanticAvailableAttr` with the resulting domain anyways.
This new attribute iterator returned from the query makes it simpler to
implement algorithms that need access to both the `AvailableAttr *` and its
corresponding `AvailabilityDomain`. This is also work towards making it
possible to return an optional `AvailabilityDomain` from
`Decl::getDomainForAvailableAttr()`.
This query's functionality was not useful enough to be exposed on `Decl` and
cached in the request evaluator. Instead, just share a local implementation of
it in `TypeCheckAttr.cpp`.
Also remove the underlying `SemanticUnavailableAttrRequest`, which used memory
very inefficiently in order to cache a detailed answer to what was usually a
much simpler question.
The only remaining use of `Decl::getSemanticUnavailableAttr()` that actually
needed to locate the semantic attribute making a declaration unavailable was in
`TypeCheckAttr.cpp`. The implementation of the request could just be used
directly in that one location. The other remaining callers only needed to know
if the decl was unavailable or not, which there are simpler queries for.
# Please enter the commit message for your changes. Lines starting
It replaces `DeclAttr::getUnavailable()` and `AvailableAttr::isUnavailable()`
as the designated way to query for the attribute that makes a decl unavailable.
The renamed decl is now stored exclusively in the split request evaluator
storage, which is more efficient since most availability attributes do not
specify a renamed decl.
Begin using `AvailabilityContext` as the availability representation in
`TypeRefinementContext`, instead of only storing platform introduction
availability ranges.
There should be no functional changes since this just changes the
representation of the existing information stored by `TypeRefinementContext`.
However, in the future `AvailabilityContext` will be expanded to represent
additional availability constraints.
This class is designed to be a compact representation of the active
availability constraints in a specific scope. For now, it only models platform
introduction availability but it will soon be updated to cover additional
availability constraints, like platform unavailability.
In anticipation of needing to reference `AvailabilityContext`s from
`TypeRefinementContext`s and increasing memory requirements for these contexts,
a cache of uniqued instances of `AvailabilityContext` are stored in a
`llvm::FoldingSet` on `ASTContext`.
