An "abstract" ProtocolConformanceRef is a conformance of a type
parameter or archetype to a given protocol. Previously, we would only
store the protocol requirement itself---but not track the actual
conforming type, requiring clients of ProtocolConformanceRef to keep
track of this information separately.
Record the conforming type as part of an abstract ProtocolConformanceRef,
so that clients will be able to recover it later. This is handled by a uniqued
AbstractConformance structure, so that ProtocolConformanceRef itself stays one
pointer.
There remain a small number of places where we create an abstract
ProtocolConformanceRef with a null type. We'll want to chip away at
those and establish some stronger invariants on the abstract conformance
in the future.
Some requirement machine work
Rename requirement to Value
Rename more things to Value
Fix integer checking for requirement
some docs and parser changes
Minor fixes
For new runtimes, this is redundant with the invertible requirement encoding, and for
old runtimes, this breaks dynamic conformance checking because Copyable and Escapable
aren't real protocols on those older runtimes. Fixes rdar://129857284.
Although I don't plan to bring over new assertions wholesale
into the current qualification branch, it's entirely possible
that various minor changes in main will use the new assertions;
having this basic support in the release branch will simplify that.
(This is why I'm adding the includes as a separate pass from
rewriting the individual assertions)
We want a conditionally-copyable type to still be classified as trivial in cases
where it's bitwise-copyable, has a trivial deinit, and is Copyable. The previous
implementation here only checked at the declaration level whether a type was
Copyable or not; get a more accurate answer by consulting the combination
of information in the substituted type and abstraction pattern we have
available during type lowering so that we classify definitely-copyable substitutions
of a conditionally-copyable type as trivial. Should fix rdar://123654553 and
rdar://123658878.
If we fail to build a generic signature (or requirement signature of a
protocol) because of a request cycle or because Knuth-Bendix completion
failed, we would create a placeholder signature with no requirements.
However in a move-only world, a completely unconstrained generic
parameter might generate spurious diagnostics when used in a copyable
way. For this reason, let's outfit these placeholder signatures with
a default set of conformance requirements to Copyable and Escapable.
We weren't diagnosing conflicts in PCT's like `Copyable & ~Copyable`,
instead deferring until that PCT was constrained to something like the
existential Self or a generic parameter, which then we'd diagnose.
But we should canonicalize PCT's such as `Copyable & Copyable` into
`Any`, which represents the empty composition. That's what the assert in
PCT::build is about.
We can't simply emit the desugared, expanded version of the requirements
because there's no way to pretty-print the type `some ~Copyable` when
the `~Copyable`'s get replaced with the absence of `Copyable`. We'd be
left with just `some _` or need to invent a new top type so we can write
`some Top`. Thus, it's best to simply reverse the expansion of default
requirements when emitting a swiftinterface file.
We already need to track the inverses separate from the members in a
ProtocolCompositionType, since inverses aren't real types. Thus, the
only purpose being served by InverseType is to be eliminated by
RequirementLowering when it appears in a conformance requirement.
Instead, we introduce separate type InverseRequirement just to keep
track of which inverses we encounter to facilitate cancelling-out
defaults and ensuring that the inverses are respected after running
the RequirementMachine.
