If a Swift key path has root type inferred but does not have a leading dot,
then diagnose it, because it's not valid.
For example:
```swift
struct Foo {
let property: [Int] = []
let kp: KeyPath<Foo, Int> = \property.count // error
}
```
Resolves SR-12290
Resolves rdar://problem/59874355
Previously we were bailing early on encountering
an optional chain in the key path. However this
could cause us to miss invalid components further
down the line. Instead, set a flag and force the
key path to be read-only if we encountered an
optional chain.
Resolves SR-12519.
This commit changes `getArgumentExprFor` to take
a ConstraintLocator argument from which to find
the argument list. This lets us properly handle
the case where we have a key path subscript
locator. In addition, this commit renames the
member to `getArgumentListExprFor` to make it
clear we're returning the argument list expression
rather than a single argument.
Resolves SR-11562.
Change `associateArgumentLabels` to take a locator
argument to enable the recording of argument
labels for individual key path components. Then
move the association of argument labels for
subscripts to `addSubscriptConstraints`, and plumb
through the argument labels for key path subscript
components.
This then allows us to correctly ignore choices
with mismatching argument labels while solving in
certain cases.
Resolves SR-11438.
Currently only valid way to form keypath subscript is to use `keyPath:`
label in subscript invocation, so let's avoid adding keypath overload
choice to every subscript lookup and instead only add it when it could
potentially match.
This among other things greatly helps diagnostics because sometimes
`keypath application` becomes the only choice even although it's
not really viable, which impedes member reference diagnostics.
Introduce a fix to detect and diagnose situations when omitted
generic arguments couldn't be deduced by the solver based on
the enclosing context.
Example:
```swift
struct S<T> {
}
_ = S() // There is not enough context to deduce `T`
```
Resolves: rdar://problem/51203824
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
Since there is a way to mutate through use of writable keypath
diagnostics have to be adjusted to point to the members found
via keypath member lookup instead to using catch-all
"immutable base" diagnostic.
Using an anonymous union in KeyPathPatternComponent instead of the weird void * in SetterAndIdKind
Added TupleElement kind to KeyPathComponentKindEncoding
Written basic SIL keypath serialization tests
Deleted or edited some old Swift-level tuple key path tests
This makes diagnostics more verbose and accurate, because
it's possible to distinguish how many parameters there are
based on the message itself.
Also there are multiple diagnostic messages in a format of
`<descriptive-kind> <decl-name> ...` that get printed as
e.g. `subscript 'subscript'` if empty labels are omitted.
`\.self` is the final chosen syntax. Implement support for this syntax, and remove the stopgap builtin and `WritableKeyPath._identity` property that were in place before.
We inadvertantly allowed this in the past, so continue to do so when
compiling in Swift 3/4 mode to avoid suddenly breaking existing code.
The diagnostic here is pretty bad, and I've opened issues for that as
well as providing some kind of deprecation warning for this so that
even under Swift 3/4 mode we alert users that this is unsupported.
rdar://problem/39802797
`AbstractStorageDecl::isSettable` by itself doesn't account for access control, so we need to check `isSetterAccessibleFrom` as well. Furthermore, key paths should not get the special context-sensitive privileges direct accesses do, such as initializers being able to assign into `let` properties. Fix the type checking logic here to only create a statically writable KeyPath value when the referenced declaration has a setter visible independent of current context. Fixes SR-6667 | rdar://problem/36257266.
When testing KeyPathApplication constraints, we would keep going after rejecting a concrete KeyPath application by trying PartialKeyPath and AnyKeyPath, even though that's not what we want, since any key path application expression can type check with an AnyKeyPath. We would then miscompile by building the AST such that we applied the mismatched key path expression directly to the base. We also didn't handle expressions where the base was a subtype of the key path's base type correctly—the conversion means the base can't be written through in this situation, and we hardcoded the concrete-to-existential case instead of handling general conversions. Fix these problems, and add an AST verifier for KeyPathApplicationExprs to help catch problems in the future. Fixes SR-6300 | rdar://problem/35368903.
We can wind up in a situation where the base of a keypath
application is concrete but is being applied to a keypath
with an existential source type. Coerce the base to the
intended type if necessary when building the final subscript
expression.
Resolves SR-5878.
