This removes all calls to typesSatisfyConstraint() except for the
isConvertibleTo() check at the beginning, in the process making the
analysis a little bit more accurate.
This helps us to better diagnose failures related to generic
requirements like `T == [Int]` as well as protocol compositions,
which require deep equality check.
Since this kind of failure is really a conversion failure, let's
inherit from `Contextual{Mismatch, Failure}` which also helps with
storage for from/to types and their resolution.
Also let's use original types involved in conversion to form
this fix, which helps to perserve all of the original sugar.
This way it covers a lot more ground and doesn't conflict with
other fixes.
Another notable change is related to check for IUO associated
with source type, that covers cases like:
```swift
func foo(_ v: NSString!) -> String {
return v
}
```
Instead of general conversion failure check for IUO enables solver
to introduce force downcast fix.
Detect and diagnose a contextual mismatch between expected
collection element type and the one provided (e.g. source
of the assignment or argument to a call) e.g.:
```swift
let _: [Int] = ["hello"]
func foo(_: [Int]) {}
foo(["hello"])
```
- Many tests got broken because of two things:
- AST dump now outputs to stdout, but many tests expected stderr. This was a straightforward fix.
- Many tests call swift with specific parameters; specifically, many call `swift frontend` directly. This makes them go through the compiler in unexpected ways, and specifically it makes them not have primary files, which breaks the new AST dump implementation. This commit adds the old implementation as a fallback for those cases, except it dumps to `stdout` to maintain some consistence.
Finally, the `/test/Driver/filelists.swift` failed for unknown reasons. It seems its output now had some lines out of order, and fixing the order made the test pass. However, as the reasons why it failed are unknown, this fix might not have been a good idea. Corrections are welcome.
When we determine that an optional value needs to be unwrapped to make
an expression type check, use notes to provide several different
Fix-It options (with descriptions) rather than always pushing users
toward '!'. Specifically, the errors + Fix-Its now looks like this:
error: value of optional type 'X?' must be unwrapped to a value of
type 'X'
f(x)
^
note: coalesce using '??' to provide a default when the optional
value contains 'nil'
f(x)
^
?? <#default value#>
note: force-unwrap using '!' to abort execution if the optional
value contains 'nil'
f(x)
^
!
Fixes rdar://problem/42081852.
`finish{Array,Dictionary}Expr` currently invoke `cs.cacheExprTypes` after building their semantic exprs, which in a nested collection expression, immediately undoes the type changes done by this peephole, leading to crashes due to inconsistencies in the AST later. rdar://problem/41040820
There are other parts of CSApply that attempt to peephole transform ArrayExprs (particularly bridging, which tries to turn `[x, y, ...] as T` into `[x as T, y as T, ...]`) and expect the elements to have already been rvalue-d. Fixes rdar://problem/40859007.
And provide better semantic background by surrounding 'nil' in ticks when it is referred to as a value
Added missing tests for certain cases involving nil capitalization
Stop creating ImplicitlyUnwrappedOptional<T> so that we can remove it
from the type system.
Enable the code that generates disjunctions for Optional<T> and
rewrites expressions based on the original declared type being 'T!'.
Most of the changes supporting this were previously merged to master,
but some things were difficult to merge to master without actually
removing IUOs from the type system:
- Dynamic member lookup and dynamic subscripting
- Changes to ensure the bridging peephole still works
Past commits have attempted to retain as much fidelity with how we
were printing things as possible. There are some cases where we still
are not printing things the same way:
- In diagnostics we will print '?' rather than '!'
- Some SourceKit and Code Completion output where we print a Type
rather than Decl.
Things like module printing via swift-ide-test attempt to print '!'
any place that we now have Optional types that were declared as IUOs.
There are some diagnostics regressions related to the fact that we can
no longer "look through" IUOs. For the same reason some output and
functionality changes in Code Completion. I have an idea of how we can
restore these, and have opened a bug to investigate doing so.
There are some small source compatibility breaks that result from
this change:
- Results of dynamic lookup that are themselves declared IUO can in
rare circumstances be inferred differently. This shows up in
test/ClangImporter/objc_parse.swift, where we have
var optStr = obj.nsstringProperty
Rather than inferring optStr to be 'String!?', we now infer this to
be 'String??', which is in line with the expectations of SE-0054.
The fact that we were only inferring the outermost IUO to be an
Optional in Swift 4 was a result of the incomplete implementation of
SE-0054 as opposed to a particular design. This should rarely cause
problems since in the common-case of actually using the property rather
than just assigning it to a value with inferred type, we will behave
the same way.
- Overloading functions with inout parameters strictly by a difference
in optionality (i.e. Optional<T> vs. ImplicitlyUnwrappedOptional<T>)
will result in an error rather than the diagnostic that was added
in Swift 4.1.
- Any place where '!' was being used where it wasn't supposed to be
allowed by SE-0054 will now treat the '!' as if it were '?'.
Swift 4.1 generates warnings for these saying that putting '!'
in that location is deprecated. These locations include for example
typealiases or any place where '!' is nested in another type like
`Int!?` or `[Int!]`.
This commit effectively means ImplicitlyUnwrappedOptional<T> is no
longer part of the type system, although I haven't actually removed
all of the code dealing with it yet.
ImplicitlyUnwrappedOptional<T> is is dead, long live implicitly
unwrapped Optional<T>!
Resolves rdar://problem/33272674.
Conditional and forced downcasts enter a constraint that almost
always succeeds; only when applying the solution do we evaluate
the feasability of the cast and determine if it always succeeds,
always fails, or conditionally succeeds. This changes how the
resulting AST is represented and can also emit diagnostics.
If the conditional cast is at this stage determined to always
succeed, we treat it as an unconditional cast, going through
ExprRewriter::coerceToType() to build the AST for the coercion.
However conditional cast constraints don't enter the same
restrictions into the solution as unconditional casts do, so
coerceToType() would fall over if casting a Swift type to a CF
type by first bridging the Swift type to Objective-C.
Get around this by checking for this case explicitly when
lowering a CoerceExpr.
It feels like there's a more fundamental issue here with how
casts are modeled in the constraint solver, but I'm not going
to try understanding that now.
Fixes <rdar://problem/32227571>.
Record the initializer type as soon as we have a solution, before
it is applied, and get the type from the constriant system instead
of from the final type checked expression.
Note that the coerceToMaterializable() was unnecessary, since we
always coerce the value to an rvalue type with coerceToType().
Eventually coerceToMaterializable() should go away.
This is mostly NFC, except using the result of simplifyType() rather
than the type of the final expression changes some diagnostics where it
appears we were previously losing sugar.
Also this accidentally fixes a crasher. Unfortunately the underlying
issue is still there (applying a solution has bugs with opened
existentials "leaking" out) -- this merely masks the problem by
getting the initializer type directly from the constriant system.
We would misreport a cast from G<T> to G<Int> or vice versa
as always failing, because we were checking for an exact
subtype relationship instead of archetype binding.
Fixes <https://bugs.swift.org/browse/SR-3609>.
When I refactored the handling of bridging conversions (e.g.,
valueType as? NSClassType), I broke the path that performed a bridging
conversion followed by a conversion to an existential, e.g.,
"some-bridged-value-type as CVarArg". Reinstate such use cases.
Fixes rdar://problem/30195862.
Checked casts are dependent on run-time queries; we should not attempt
to infer type variable bindings from them, because doing so produces
unreasonable bindings. Fixes rdar://problem/29894174.
Force unwrapping the expression and propagating that type down to the
rest of the tree causes crashes when we go to request a different set
of protocols than we were expecting from it later. Make this
transformation local to the apply instead.
Specialize and improve the "downcast only unwraps optionals"
diagnostic to provide specific diagnostics + Fix-Its for the various
casts of forced cast, conditional cast, and "isa" check. Specifically:
* With a forced cast, customize the diagnostic. We still insert the
appropriate number of !'s, but now we remove the 'as! T' (if an
implicit conversion would suffice) or replace the 'as!' with 'as'
(if we still need a bridge)
* With a conditional cast, only emit a diagnostic if we're removing
just one level of optional. In such cases, we either have a no-op
(an implicit conversion would do) or we could just use 'as' to the
optional type, so emit a customized warning to do that. If we are
removing more than one level of optional, don't complain:
conditional casts can remove optionals. Add the appropriate Fix-Its
here.
* With an 'is' expression, only emit a diagnostic if we're removing
just one level of optional. In this case, the 'is' check is
equivalent to '!= nil'. Add a Fix-It for that.
Across the board, reduce the error to a warning. These are
semantically-well-formed casts, it's just that they could be written
better.
Fixes rdar://problem/28856049 and rdar://problem/22275685.
The type checker implements logic for handling checked casts in two
places: the constraint solver (for type-checking expressions
containing "as!" or "as?") and as a top-level entrypoint for
type-checking as?/as! for diagnostics and is/as patterns. Needless to
say, the two implementations were inconsistent, and in fact both were
wrong, leading to various problems---rejecting perfectly-valid "as!"
and "as?" casts outright, bogus warnings that particular as!/as? casts
always-succeed or always-fail when they wouldn't, and so on.
Start detangling the mess in two ways. First, drastically simplify the
handling of checked casts in the constraint solver, eliminating the
unprincipled "subtype" constraint checks that (among other things)
broke the handling of checked casts that involved bridging or optional
unwrapping. The simpler code is more permissive and more correct; it
essentially accepts that the user knows what she is doing with the
cast.
Second, make the type checker's checking of casts far more thorough,
which includes:
* When we're performing a collection cast, actually check that the
element types (and key types, for a dictionary) are castable, rather
than assuming all collection casts are legitimate. This means we'll
get more useful "always fails" and "always succeeds" diagnostics for
array/set/dictionary.
* Handle casts from a bridged value type to a subclass of the
corresponding bridged class type. Previously, these would be
incorrectly classified as "always fails".
While I'm here, eliminate a spurious diagnostic that occurs when using
a conditional cast ("as?") that could have been a coercion/bridging
conversion ("as"). The optional injection we synthesize to get the
resulting type correct was getting diagnosed as an implicit coercion,
but shouldn't have been.
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.
