Not quite NFC because apparently the representation bleeds into what's
accepted in some situations where we're supposed to be warning about
conflicts and then making an arbitrary choice. But what we're doing
is nonsense, so we definitely need to break behavior here.
This is setting up for isolated(any) and isolated(caller). I tried
to keep that out of the patch as much as possible, though.
It should be the responsibility of callers to map the type to a
contextual type, as needed. When it's not possible or repetitive to do
so, there is a special-purpose function `isInterfaceTypeNoncopyable` for
Sema.
Handle requirement failures in result builder `build*` methods explicitly
and give them a high impact rating because issues if such positions
imply that the transform didn't work and it shouldn't shadow errors
in user code.
Resolves: rdar://111120803
Resolves: rdar://120342129
Doing so improves performance if closure is passed as an argument
to a (heavily) overloaded declaration, avoid unrelated errors,
propagate holes, and record a more impactful fix.
Start classifying all potential throw sites within a constraint
system and associate them with the nearest enclosing catch node. Then,
determine the thrown error type for a given catch node by taking the
union of the thrown errors at each potential throw site. Use this to
compute the error type thrown from the body of a `do..catch` block
within a closure.
This behavior is limited to the upcoming feature `FullTypedThrows`.
The errorUnion type operation specifies how thrown error types are
combined when multiple errors are thrown in the same context. When
thrown error types can have type variables in them, we sometimes cannot
resolve the errorUnion until the type variables have substitutions. In
such cases, we need to persist the result of errorUnion in the
constraint solver.
Introduce the ErrorUnionType to do exactly that, and update the core
errorUnion operation to produce an ErrorUnionType when needed. At
present, this code is inert, because any errorUnion operation today
involves only concrete types. However, inference of thrown errors in
closures will introduce type variables, and depend on this.
We already need to track the inverses separate from the members in a
ProtocolCompositionType, since inverses aren't real types. Thus, the
only purpose being served by InverseType is to be eliminated by
RequirementLowering when it appears in a conformance requirement.
Instead, we introduce separate type InverseRequirement just to keep
track of which inverses we encounter to facilitate cancelling-out
defaults and ensuring that the inverses are respected after running
the RequirementMachine.
Avoid delaying if:
- Base is a metatype because static methods are always Sendable
(because metatype is Sendable)
- Lookup doesn't have any methods (properties are un-affected by
the inference changes).
A way to mark key path as Sendable is to extend its type with `& Sendable`.
This is something that makes the type of a key path expression an existential
with superclass bound expressed as a known key path type.
In general the solver attempts to gather all of the generic argument
mismatches into a single fix because there could be an arbitrary
number of generic arguments. This is uncessary for key path literals
matching against a contextual type because they have at most two
generic arguments (Root and Value), so it's better to produce fixes
for root and value type individually.
Since key path root is now transitively inferred. Key path type
inference can be delayed until key path is resolved enough to
infer its capability.
This solves multiple problems:
- Inference fully controls what key path type is bound to;
- KeyPath constraint simplification doesn't have to double-check
the capability and attempt to re-bind key path type;
- Custom logic to resolve key path type is no longer necessary;
- Diagnostics are improved because capability and root/value type
mismatch are diagnosed when key path is matched against the
contextual type.
When "optional type" is a hole the simplification logic has to
simplify "object type" and mark all of its unresolved components
are potential holes, otherwise hole propagation won't work since
sometimes there is no other contextual information for such types
but "optional type".
Resolves: rdar://117871338
Move some of the checks from the constraint simplification into
`inferKeyPathLiteralCapability` and start using it for both
inference and constraint simplification.
