There were various problems with layout constraints either
being ignored or handled incorrectly. Now that I've exercised
this support with an upcoming patch, there are some fixes
here.
Also, introduce a new ExistentialLayout::getLayoutConstriant()
which returns a value for existentials which are class-constrained
but don't have a superclass or any class-constrained protocols;
an example would be AnyObject, or AnyObject & P for some
non-class protocol P.
NFC for now, since these layout-constrained existentials cannot
be constructed yet.
This is an initial implementation of the constraint propagation pass,
disabled by default at the moment as it does not currently pass all
tests.
I have other changes that I'll hold off on for now because they are
incomplete. Without those changes, this pass doesn't really achieve
much, so this is really just a checkpoint on some progress and not
something really worth trying out at this point.
Without this, CSGen/CSSimplify and CSApply may have differing
opinions about whether e.g. a let property is settable, which
can lead to invalid ASTs.
Arguably, a better fix would be to remove the dependency on the
exact nested DC. For example, we could treat lets as settable
in all contexts and then just complain later about invalid
attempts to set them. Or we could change CSApply to directly
use the information it already has about how an l-value is used,
rather than trying to figure out whether it *might* be getting set.
But somehow, tracking a new piece of information through the
entire constraint system seems to be the more minimal change.
Fixes rdar://29810997.
This commit introduces new kind of requirements: layout requirements.
This kind of requirements allows to expose that a type should satisfy certain layout properties, e.g. it should be a trivial type, have a given size and alignment, etc.
withoutActuallyEscaping has a signature like `<T..., U, V, W> (@nonescaping (T...) throws<U> -> V, (@escaping (T...) throws<U> -> V) -> W) -> W, but our type system for functions unfortunately isn't quite that expressive yet, so we need to special-case it. Set up the necessary type system when resolving an overload set to reference withoutActuallyEscaping, and if a type check succeeds, build a MakeTemporarilyEscapableExpr to represent it in the type-checked AST.
Previously, bridging conversions were handled as a form of "explicit
conversion" that was treated along the same path as normal
conversions in matchTypes(). Historically, this made some
sense---bridging was just another form of conversion---however, Swift
now separates out bridging into a different kind of conversion that is
available only via an explicit "as". This change accomplishes a few
things:
* Improves type inference around "as" coercions. We were incorrectly
inferring type variables of the "x" in "x as T" in cases where a
bridging conversion was expected, which cause some type inference
failures (e.g., the SR-3319 regression).
* Detangles checking for bridging conversions from other conversions,
so it's easier to isolate when we're applying a bridging
conversion.
* Explicitly handle optionals when dealing with bridging conversions,
addressing a number of problems with incorrect diagnostics, e.g.,
complains about "unrelated type" cast failures that would succeed at
runtime.
Addresses rdar://problem/29496775 / SR-3319 / SR-2365.
The 'literalConformanceProto' field of
TypeVariableType::Implementation didn't take into account equivalence
classes of type variables. Eliminate it, and either look at the actual
expressions (for optimizing constraints during constraint generation)
or the actual constraints on a given type variable (for determining
whether to include optionals in the set of potential type variable
bindings).
(cherry picked from commit 6bdd9cfae5)
This reverts commit 6bdd9cfae5. This
commit *appears* to be breaking something in Dollar involving
inference with array literals and 'nil'; pull it back for more
investigation.
The 'literalConformanceProto' field of
TypeVariableType::Implementation didn't take into account equivalence
classes of type variables. Eliminate it, and either look at the actual
expressions (for optimizing constraints during constraint generation)
or the actual constraints on a given type variable (for determining
whether to include optionals in the set of potential type variable
bindings).
Simplify e.g., ASTContext::getBridgedToObjC(), which no longer needs
the optional return.
Eliminate the now-unused constraint kind for checking bridging to
Objective-C.
Extend the handling of function reference kinds to member references
(e.g., x.f), and therefore the logic for stripping argument labels. We
appear to be stripping argument labels from all of the places where it
is required.
When referencing a function in the type checker, drop argument labels
when we don't need them to type-check an immediate call to that
function. This provides the semantic behavior of SE-0111, e.g.,
references to functions as values produce unlabeled function types,
without the representational change of actually dropping argument
labels from the type system.
At the moment, this only works for bare references to functions. It
still needs to be pushed through more of the type checker and more AST
nodes to work in the general case.
Keep this work behind the frontend flag
-suppress-argument-labels-in-types for now.
This reverts commit dc24c2bd34.
Turns out Chris fixed the build but when I was looking at the bots, his fix had
not been tested yet, so I thought the tree was still red and was trying to
revert to green.
Introduce bridging of NSError to ErrorProtocol, so an Objective-C API
expressed via an "NSError *" will be imported using ErrorProtocol in
the Swift. For example, the Objective-C method:
- (void)handleError:(NSError *)error userInteractionPermitted:(BOOL)userInteractionPermitted;
will now be imported as:
func handleError(_ error: ErrorProtocol, userInteractionPermitted: Bool)
This is bullet (3) under the proposed solution of SE-0112. Note that
we made one semantic change here: instead of removing the conformance
of NSError to ErrorProtocol, which caused numerous problems both
theoretical and actual because the model expects that an NSError
conforms to ErrorProtocol without requiring wrapping, we instead limit
the ErrorProtocol -> NSError conversion that would be implied by
bridging. This is defensible in the short term because it also
eliminates the implicit conversion, and aligns with SE-0072, which
eliminates implicit bridging conversions altogether.
In member ref expressions, if the base is optional, and the expected
expression result is either optional or unknown, suggest a fixit that
makes it into an optional chain expr rather than force unwrapping.
Since in many cases the actual fixit is emitted during diagnosis, and
thus, while type checking sub exprs with no contextual type specified
(so nothing to check for preferring optionality), we also need an
additional flag to pass down from FailureDiagnosis for whether we
prefer to fix as force unwrapping or optional chaining.
I attempted to do this same job via providing a convert type but
setting the ConvertTypeIsOnlyAHint flag on the type checker, but
unfortunately there are a lot of other moving parts that look at that
type, even if it is only supposed to be a hint, so an additional flag
to the CS ended up being cleaner.
The issue here is that the constraint solver was deciding on
FixKind::RelabelCallTuple as the fix for the problem and emitting the
diagnostic, even though there were two different fixes possible.
CSDiags has the infrastructure to support doing doing the right thing
here, but is only being used for ApplyExprs, not SubscriptExprs.
The solution is to fix both problems: remove FixKind::RelabelCallTuple,
to let CSDiags handle the problem, and enhance CSDiags to treat
SubscriptExpr more commonly with ApplyExpr. This improves several cases
where the solver was picking one solution randomly and suggesting that
as a fix, instead of listing that there are multiple different solutions.
Introduce a new constraint kind, BindParam, which relates the type of a
function parameter to the type of a reference to it from within the
function body. If the param type is an inout type, the ref type is an
lvalue type with the same underlying object type; otherwise the two
types must be the same. This prevents DeclRefExprs from being inferred
to have inout type in some cases.
<rdar://problem/15998821> Fail to infer types for closure that takes an inout argument
Swift SVN r32183
with no returns *must* be (), add a defaulting constraint
so that it will be inferred as () in the absence of
other possibilities.
The chief benefit here is that it allows better QoI when
the user simply hasn't yet written the return statement.
Doing this does regress a corner case where an attempt
to recover from an uncalled function leads to the
type-checker inferring a result for a closure that
doesn't make any sense at all.
Swift SVN r30476
X.Protocol is an instance of Y.Type only if X conforms to Y. Since X
is a protocol, this is only true if X contains Y and Y is
self-conforming.
Note that this updates some tests that actually contained invalid code.
Fixes <rdar://problem/20915927>.
Swift SVN r29349
