A request is intended to be a pure function of its inputs. That function could, in theory, fail. In practice, there were basically no requests taking advantage of this ability - the few that were using it to explicitly detect cycles can just return reasonable defaults instead of forwarding the error on up the stack.
This is because cycles are checked by *the Evaluator*, and are unwound by the Evaluator.
Therefore, restore the idea that the evaluate functions are themselves pure, but keep the idea that *evaluation* of those requests may fail. This model enables the best of both worlds: we not only keep the evaluator flexible enough to handle future use cases like cancellation and diagnostic invalidation, but also request-based dependencies using the values computed at the evaluation points. These aforementioned use cases would use the llvm::Expected interface and the regular evaluation-point interface respectively.
Introduce `SK_Hole` which is used to count a number of "holes" in
a given solution. It is used to distinguish solutions with fewer holes.
Also it makes it possible to check whether a solution has holes but
no fixes, which is an issue and such solution shouldn't be applied
to AST.
If constraint system is underconstrained e.g. because there are
editor placeholders, it's possible to end up with multiple solutions
where each ambiguous declaration is going to have its own overload kind:
```swift
func foo(_: Int) -> [Int] { ... }
func foo(_: Double) -> (result: String, count: Int) { ... }
_ = foo(<#arg#>).count
```
In this case solver would produce 2 solutions: one where `count`
is a property reference on `[Int]` and another one is tuple access
for a `count:` element.
Resolves: rdar://problem/49712598
Single type of keypath dynamic member lookup could refer to different
member overlaods, we have to do a pair-wise comparison in such cases
otherwise ranking would miss some viable information e.g.
`_ = arr[0..<3]` could refer to subscript through writable or read-only
key path and each of them could also pick overload which returns `Slice<T>`
or `ArraySlice<T>` (assuming that `arr` is something like `Box<[Int]>`).
Instead of trying to hold a "global" set of type variable differences
let's use pair-wise comparison instead because in presence of generic
overloads such would be more precise.
If there are N solutions for a single generic overload we currently
relied on "local" comparison to detect the difference, but it's not
always possible to split the system to do one. Which means higher
level comparisons have to account for "local" (per overload choice)
differences as well otherwise ranking would loose precision.
Motivation: `GenericSignatureImpl::getCanonicalSignature` crashes for
`GenericSignature` with underlying `nullptr`. This led to verbose workarounds
when computing `CanGenericSignature` from `GenericSignature`.
Solution: `GenericSignature::getCanonicalSignature` is a wrapper around
`GenericSignatureImpl::getCanonicalSignature` that returns the canonical
signature, or `nullptr` if the underlying pointer is `nullptr`.
Rewrite all verbose workarounds using `GenericSignature::getCanonicalSignature`.
This commit changes the behaviour of the error for
passing a temporary pointer conversion to an
@_nonEphemeral parameter such that it doesn't
affect overload resolution. This is done by recording
the fix with an impact of zero, meaning that we don't
touch the solution's score.
In addition, this change means we no longer need
to perform the ranking hack where we favour
array-to-pointer, as the disjunction short-circuiting
will continue to happen even with the fix recorded.
Use ProtocolConformanceRef::forInvalid() in implementations only as a semantic signal. In one place, use the default constructor to drop the final use of Optional<ProtocolConformanceRef>.
ProtocolConformanceRef already has an invalid state. Drop all of the
uses of Optional<ProtocolConformanceRef> and just use
ProtocolConformanceRef::forInvalid() to represent it. Mechanically
translate all of the callers and callsites to use this new
representation.
Structurally prevent a number of common anti-patterns involving generic
signatures by separating the interface into GenericSignature and the
implementation into GenericSignatureBase. In particular, this allows
the comparison operators to be deleted which forces callers to
canonicalize the signature or ask to compare pointers explicitly.
This only comes into play when all other choices are coming from
constrained extensions, because there is no way to determine upfront
whether any are going to match it's better to be safe and add
key path dynamic member choice to the set too.
Resolves: [SR-11465](https://bugs.swift.org/browse/SR-11465)
Resolves: rdar://problem/55314724
While it's currently not possible for `isDeclAsSpecializedAs` to compare
decls that differ by having a curried self or having a parameter list,
tweak the logic slightly so it could handle that case if it needed to.
If one decl has a parameter list and the other doesn't, then just
compare their self types. If one decl is curried and the other isn't,
then add a curried self to the other and compare as normal.
Use this function to replace various places where the logic is
duplicated.
In addition, isolate the logic where subscripts are treated as having
curried self parameters to CalleeCandidateInfo, as their interface types
don't have a curried self, but get curried with self by
CalleeCandidateInfo. Ideally we'd fix this by having a subscript's
interface type be curried with self, but given that most of this CSDiag
logic should be going away, this may not be necessary.
Introduce an attribute @_disfavoredOverload that can be used to state
that a particular declaration should be avoided if there is a
successful type-check for a non-@_disfavoredOverload. It's a way to
nudge overload resolution away from particular solutions.
Instead of storing information about expression depths in the
solver state (which gets recomputed for salvage) let's track
it directly in constraint system, which also gives solver
access to it when needed e.g. for fixes.
Solving Bind is a little easier than Equal. The only remaining uses of Equal
are in the .member syntax and keypaths; if we can refactor those, we might be
able to simplify LValue handling in the type checker in general.
We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.
Patch produced by
for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done
Make sure that presence of `@autoclosure` attribute handled
in one place - `matchCallArguments`, which makes it possible
to remove the rest of (now redundant) autoclosure related
logic scattered throughout solver.
