If the contextual type propagated into the optional chain mismatches with
the inner type formed from its member references and that inner type
is a result of some fix, let's consider that un-salvageable and avoid
producing additional "ignore contextual type" fixes which only lead
to subpar solutions.
I'm not really convinced that this shouldn't be done by introducing a new
kind of constraint rather than hacking in what are essentially conversions
as "bind" constraints, but this is the most direct path for now.
Fixes rdar://125394096
The condition that the conforming type satisfies the superclass bound
of the conformed protocol is already covered by the conformance constraint
itself.
Since importer ignored `swift_attr` that appeared in a type context
until recently we need to maintain status quo with concurrency stripping
from ObjC requirements in modes that don't have full concurrency
checking enabled.
Even if the member type variable is partially resolved, we still need
to mark inner type variables (if any) as holes because they might not
be connected to anything that could provide contextual type(s).
Resolves: rdar://124549952
To maintain source compatibility, SE-0352 does not open existentials
with "self-conforming" type, such as `any Error` or existentials based
on `@objc` protocols. The proposal specified that this behavior would
change in Swift 6. Implement that behavior change, which can be
enabled prior to Swift 6 with the upcoming feature
`ImplicitOpenExistentials` (as documented in SE-0362).
Fixes#70873 / rdar://120902975.
Although inference doesn't allow direct bindings to
type variables, they can still get through via `matchTypes`
when type is a partially resolved pack expansion that simplifies
down to a type variable.
When a NoncopyableGenericsMismatch happens between the compiler and
stdlib, allow the compiler to rebuild the stdlib from its interface
instead of exiting with an error.
Instead of handing failures in `matchWitness` let's syntehsize
conformances during solving. Next step would be to record them
and use in `Solution::computeSubstitutions`.
Previously, if a request R evaluated itself N times, we would emit N
"circular reference" diagnostics. These add no value, so instead let's
cache the user-provided default value on the first circular evaluation.
This changes things slightly so that instead of returning an
llvm::Expected<Request::OutputType>, various evaluator methods take
a callback which can produce the default value.
The existing evaluateOrDefault() interface is unchanged, and a new
evaluateOrFatal() entry point replaces
llvm::cantFail(ctx.evaluator(...)).
Direct callers of the evaluator's operator() were updated to pass in
the callback. The benefit of the callback over evaluateOrDefault() is
that if the default value is expensive to constuct, like a dummy
generic signature, we will only construct it in the case where a
cycle actually happened, otherwise we just delete the callback.
(cherry picked from commit b8fcf1c709efa6cd28e1217bd0efe876f7c0d2b7)
In some cases we get a `ConstraintKind::SelfObjectOfProtocol` here.
That's typically for an existential cast. In such a case, we actually
get a better standard diagnostic than what MustBeCopyable can produce
currently. So this change narrows things to what MustBeCopyable is
better at diagnosing.
