If a requirement is made redundant due to another requirement that was
inferred from the signature of a generic declaration, don't diagnose
the former as redundant. The user has likely written the requirement
explicitly for clarity purposes (e.g., to emphasize the Hashable
requirement on a function that takes a Set<T>). Removing the
requirement to silence the warning would make the code less clear.
This eliminates all of the annoying, spurious warnings from the build
of the overlays.
The ad hoc substitution functions here were really odd; use
SubstitutionMap directly, and pass it through to
GenericSignatureBuilder::addRequirement().
The stored dependent types in ProtocolRequirement elements within
requirement sources were incorrect for requirements created from the
requirement signature of another protocol, because we picked up the
already-substituted subject type. Thread the optional substitution map
through addRequirement(Requirement) as well, so we maintain the
original spelling of the stored dependent type.
This is a temporary fix; we should be able to recover the stored
dependent types from the potential archetypes in the requirement
source, so that we don't need to specify them explicitly at
construction time.
For a protocol requirement element within a requirement source, track
both the protocol in which the requirement was introduced as well as
the dependent type (relative to that protocol) on which the
requirement was introduced. This information is important when
reconstructing the path from a requirement-as-written to the location
of a desired protocol conformance.
Start reshuffling RequirementSource to store more information about
requirements in protocols. As a small step, track the source locations
for requirements written within the protocols themselves.
Note: there's a QoI regression here where we get duplicated
diagnostics (due to multiple generic signature builders being built
from a bad signature).
The use of floating sources allows us to carry through the protocol
information (i.e., "in which protocol do we look for this
information?") without immediately forming a new
RequirementSource. Yet more NFC refactoring for protocol-requirement
sources to carry more pertinent information.
This got reverted because it made our non-deterministic deserialization
crasher come up more often. Re-applying this patch to test the theory
that @jrose-apple's fix addressed the issue.
Centralize the checking of a superclass constraint against a
same-type-to-concrete constraint. Additionally, produce a warning if
the superclass constraint is satisfied but is made redundant by an
existing same-type constraint.
Use the same infrastructure we have for same-type-to-concrete
constraints to check superclass constraints. Specifically,
* Track all superclass constraints; never "update" a requirement source
* Remove self-derived superclass constraints
* Pick the best superclass constraint within each connected component
of an equivalence class and use that for requirement generation.
* Diagnose conflicting superclass requirements during finalization
* Diagnose redundant superclass requirements (during finalization)
Introduce an operation on RequirementSource to determine whether a
constraint with such a source, when it lands on a given potential
archetype, is "self-derived": e.g., the final constraint is derived
from the original constraint. Remove such constraints from the system
during finalization, because otherwise they would make the original
constraint redundant.
Fixes rdar://problem/30478915, although we still need to apply this
same logic to other kinds of constraints in the system.
Use TrailingObjects to help us efficiently store the root potential
archetype within requirement sources, so we can reconstruct the
complete path from the point where a requirement was created to the
potential archetype it affects.
The test changes are because we are now dumping the root potential
archetype as part of -debug-generic-signatures.
Whenever we create a (root) requirement source, associate it with the
potential archetype on which the requirement is written. This lets us
follow a requirement source from the (stated or implied) requirement on
the root potential archetype to the effective requirement on the
resulting potential archetype.
Introduce FloatingRequirementSource for the cases where we need to
state what the root source is, but don't yet have a potential
archetype to attach it to. These get internally resolved to
RequirementSources as soon as possible.
Most clients that will be considering same-type-to-concrete
constraints will need to look at all of the constraints within the
equivalence class together. Store the same-type-to-concrete
constraints on the EquivalenceClass itself, which fits this use case
better, and should reduce the storage requirements by making potential
archetypes two pointers smaller. NFC
When we see a second same-type-to-concrete constraint on a particular
potential archetype, record it. Previously, we were checking it and
then updating the requirement source eagerly. That won't work with
proper recursion detection, and meant that we missed out on some
obvious redundant-same-type-constraint diagnostics.
The scheme here is to build up the equivalence classes without losing
any information, and then determine which information is redundant at
the end.
Introduce an equivalence-class abstraction that captures all of the
members of the equivalence class in a separate type that will maintain
the "truth" about the meaning of the equivalence class, rather than
having that information distributed amongst the potential archetypes
within the class.
For now, use it to capture the members of the equivalence classes, so
we have one SmallVector per equivalence class rather than N
SmallVectors.
Diagnose when a same-type constraint (to a concrete type) is made
redundant by another same-type constraint. Slightly improve the
diagnostic that handles collisions between two same-type constraints.
When a type parameter is made concrete via an existential type,
conformance requirements on that type parameter will be
abstract. Fixes rdar://problem/30610428.
`GenericSignatureBuilder::resolve()` was always jumping to the
representative, to treat typealias representatives as
special. However, doing this means that we put the same-type
constraint on the wrong potential archetype (with the wrong source).
Eliminate the use of `getRepresentative()`. This unfortunately
causes us to need recursive resolution, because we can't always depend
on jumping to the representative to avoid it.
Track each same-type-to-concrete constraint on the potential archetype
against which it was written, and ensure that the requirement sources
for such same-type constraints stay with the potential archetypes on
which they were described. This is similar to the way we track
same-type constraints among potential archetypes.
Use this information to canonicalize same-type-to-concrete constraints
appropriately. For each connected component within an equivalence
class of potential archetypes, select the best requirement source to
the concrete type, or substitute in an abstract requirement source if
none exists. This approach ensures that components that would be
equivalent to that concrete type anyway get a derived source, while
components that get the concrete-type equivalence by being tied to
another
To get here, we also needed to change the notion of the archetype
anchor so that potential archetypes with no same-type constraints
directly in their path are preferred over potential archetypes that do
have a same-type constraint in their path. Otherwise, the anchor might
be something that is always concrete and is, therefore, not terribly
interesting.
Fixes the new case that popped up in rdar://problem/30478915.
