Enhance call-argument matching to reject trailing closures that match up
with parameters that cannot accept closures at all.
Fixes rdar://problem/50362170.
Detect situations where key path doesn't have capability required
by the context e.g. read-only vs. writable, or either root or value
types are incorrect e.g.
```swift
struct S { let foo: Int }
let _: WritableKeyPath<S, Int> = \.foo
```
Here context requires a writable key path but `foo` property is
read-only.
Currently `getPotentialBindingsForRelationalConstraint` doesn't
respect the fact that type of key path expression has to be a
form of `KeyPath`, instead it could eagerly try to bind it to
`Any` or other contextual type if it's only available
information.
This patch aims to fix this situation by filtering potential
bindings available for type variable representing type of
the key path expression.
Resolves: SR-10467
We have a systemic class of issues where noescape types end up bound to
type variables in places that should not. The existing diagnostic for
this is ad-hoc and duplicated in several places but it doesn't actually
address the root cause of the problem.
For now, I've changed all call sites of createTypeVariable() to set the
new flag. I plan on removing enough occurrences of the flag to replicate
the old diagnostics. Then we can continue to refine this over time.
Implicit argument expression was necessary to generate keypath
constraint which is used to validate a choice picked for the member.
But since read-only check has been factored out it's now possible
to validate choice directly in combination with new 'keypath dynamic lookup'
locator associated with member type variable which represents result
of the dynamic lookup.
Instead of waiting until the overload is attempted, let's figure out
if there is anything wrong with it beforehand and attach a fix to the
"bind overload" constraint representing it.
Further simplify `addOverloadSet` and move "outer" candidate handling
to the only place where it comes up - `simplifyMemberConstraint`.
Also move constraint generation for choices into a separate method.
This is a stepping stone on the path to enable attaching fixes to
the overload choices.
- Remove whole disjunction favoring which has no effect;
- Avoid creating separate disjunction for "inner" choices,
which is going to be flattened later anyway.
When we’re trying to find the overload set corresponding to a particular
type variable, look through “optional object of” constraints that represent
the use of ? binding or ! forcing. This allows us to find overload sets
when referring to, e.g., @objc optional protocol requirements.
This narrow favoring rule makes more sense as part of disjunction
partitioning, because it is not dependent on the use site at all and
should only kick in when other options fail.
The "common type" optimization isn't really buying us anything at this
point, because we're not able to make much use of the common structure
often enough. Revert the "common type" optimization for now... I'll
bring it back when there's enough optimization infrastructure around
it to make it compelling.
The walker that was setting argument labels was looking through ! and ?
postfix expressions, but the lookup code itself was not, leading to missed
opportunities for filtering based on argument labels. Generalize the
transformation that maps from the function expression down to the locator
for which we will retrieve argument labels.
When simplifying a function application constraint, check the argument
labels for that application against the disjunction containing the overload
set, disabling any overloads with mis-matching labels. This is staging for
several different directions:
* Eliminating the argument label matching from performMemberLookup, where it
does not belong
* More aggressively filtering the overload set when we have some concrete
information about argument types
* Identifying favored constraints when we have some concrete information
about argument types
At present, the only easily-visible effect of this change is that
we now properly handle argument label matching for non-member functions.
Constraint generation for function application expressions contains a simple
hack to try to find the common result type for an overload set containing
callable things. Instead, perform this “common result type” computation
when simplifying an applicable function constraint, so it is more
widely applicable.
Given an overload set, attempt to compute a "common type" that
abstracts over all entries in the overload set, providing more
structure for the constraint solver.
Extend existing `RequirementFailure` functionality to support
conditional requirement failures. Such fixes are introduced
only if the parent type requirement has been matched successfully.
Resolves: rdar://problem/47871590
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.
This helps to postpone attempting bindings related to generic
parameters with all else being equal.
Consider situation when function has class requirement on its
generic parameter. Without such requirement solver would infer
sub-class for `T`. But currently when requirement is present base
class is inferred instead, because when bindings for such generic
parameter are attempted early single available binding at that
point comes from the requirement.
```swift
class BaseClass {}
class SubClass: BaseClass {}
struct Box<T> { init(_: T.Type) {} }
func test<T: BaseClass>(box: Box<T>) -> T.Type {
return T.self
}
test(box: .init(SubClass.self)) // `T` expected to be `SubClass`
```
Resolves: [SR-9626](https://bugs.swift.org/browse/SR-9626)
Resolves: rdar://problem/47324309
