A type representing a closure expression is always bound to its
"inferred" type based on the body, so contextual bindings just
serve as a trigger to "resolve" a closure. Let's not attempt any
subtype/supertype inference for a type variable representing a
closure since if "direct" bindings have failed, it wouldn't be bound
to such types regardless.
Resolves: rdar://problem/77022842
If left-hand side of a conversion that requires l-value is a placeholder type,
let's fix that by propagating placeholder to the order side (to allow it to
infer a placeholder if needed) without recording a fix since placeholder can
be converted to `inout` and/or l-value and already indicates existence of a
problem at some other spot in the expression.
Resolves: rdar://76250381
If there is a contextual mismatch associated with a closure body,
make sure that the diagnostic is attached to the closure even
if the body is empty or implicit.
Resolves: rdar://52204608
Performance optimization.
If there is a concrete contextual type we could use, let's bind
it to the external type right away because internal type has to
be equal to that type anyway (through `BindParam` on external type
i.e. <internal> bind param <external> conv <concrete contextual>).
```swift
func test(_: ([String]) -> Void) {}
test { $0 == ["a", "b"] }
```
Without this optimization for almost all overloads of `==`
expect for one on `Equatable` and one on `Array` solver would
have to repeatedly try the same `[String]` type for `$0` and
fail, which does nothing expect hurts performance.
Resolves: rdar://19836070
Resolves: rdar://19357292
Resolves: rdar://75476311
Detect that direct callee couldn't be resolved e.g. due to an
invalid reference or a missing member and fail instead of
triggering an assert.
Resolves: rdar://problem/71525503
The change to the forward-scanning rule regressed some diagnostics,
because we no longer generated the special "trailing closure mismatch"
diagnostic. Reinstate the special-case "trailing closure mismatch"
diagnostic, but this time do so as part of the normal argument
mismatch diagnostics so it is based on type information.
While here, clean up the handling of missing-argument diagnostics to
deal with (multiple) trailing closures properly, so that we can (e.g)
suggest adding a new labeled trailing closure at the end, rather than
producing nonsensical Fix-Its.
And, note that SR-12291 is broken (again) by the forward-scan matching
rules.
Detect situation when it's impossible to determine types for
closure parameters used in the body from the context. E.g.
when a call closure is associated with refers to a missing
member.
```swift
struct S {
}
S.foo { a, b in } // `S` doesn't have static member `foo`
let _ = { v in } // not enough context to infer type of `v`
_ = .foo { v in } // base type for `.foo` couldn't be determined
```
Resolves: [SR-12815](https://bugs.swift.org/browse/SR-12815)
Resolves: rdar://problem/63230293
Accept trailing closures in following form:
```swift
foo {
<label-1>: { ... }
<label-2>: { ... }
...
<label-N>: { ... }
}
```
Consider each labeled block to be a regular argument to a call or subscript,
so the result of parser looks like this:
```swift
foo(<label-1>: { ... }, ..., <label-N>: { ... })
```
Note that in this example parens surrounding parameter list are implicit
and for the cases when they are given by the user e.g.
```swift
foo(bar) {
<label-1>: { ... }
...
}
```
location of `)` is changed to a location of `}` to make sure that call
"covers" all of the transformed arguments and parser result would look
like this:
```swift
foo(bar,
<label-1>: { ... }
)
```
Resolves: rdar://problem/59203764
Instead of setting empty closure (`{}`) result type to be `Void`
while generating constraints, let's allocate a new type variable
instead and let it be bound to `Void` once the body is opened.
This way we can support an interaction with function builders which
would return a type different from `Void` even when applied to empty closure.
Resolves: rdar://problem/61347993
Previously we could skip default literal or
supertype bindings if we had already found a solution
with fixes, which could lead us to miss bindings
that produce better diagnostics.
Tweak the logic such that we continue exploring if
we're in diagnostic mode.
Resolves SR-12399.
It's allowed to convert a single statement closure from `(...) -> T` to `(...) -> Void`
_only_ if there is no explicit `return` in the body.
Resolves: [SR-12277](https://bugs.swift.org/browse/SR-12277)
Resolves: rdar://problem/52204414
Reverts apple/swift#30006. It caused a regression that we'd like to address before re-landing:
```swift
struct X {
var cgf: CGFloat
}
func test(x: X?) {
let _ = (x?.cgf ?? 0) <= 0.5
}
```
This reverts commit 0a6b444b49.
This reverts commit ed255596a6.
This reverts commit 3e01160a2f.
This reverts commit 96297b7e39.
Resolves: rdar://problem/60185506
parseClosureSignatureIfPresent.
Otherwise, closure parameters that were parsed as "potentially destructured"
will fail constraint generation, even after the parser has decided
they are not destructured.
Let's delay attempting any bindings for type variables representing
parameters or result type of the closure until the body is "opened"
because it's impossible to infer a full set of bindings until all
constraints related to a closure have been generated.
Resolves: rdar://problem/59741308
Fix a case where favoring didn't account for "bound" type variable
being wrapped into optional(s) (disjunctions like that are used for
optional conversions). Doing so makes sure that closure result type
is not bound before the body of the closure is "opened", that's
important because body could provide additional context required
to bind result type e.g. `{ $0 as? <Type> }`.
Resolve: rdar://problem/59208419
Delayed constraint generation for the body of the single-statement
closures regressed variadic parameter handling. Fix it by using
`FunctionType::Param::getParameterType` for "internal" version of
the parameter type which translates variadic/inout correctly.
Resolved: rdar://problem/58647769
Instead of trying to hold a "global" set of type variable differences
let's use pair-wise comparison instead because in presence of generic
overloads such would be more precise.
If there are N solutions for a single generic overload we currently
relied on "local" comparison to detect the difference, but it's not
always possible to split the system to do one. Which means higher
level comparisons have to account for "local" (per overload choice)
differences as well otherwise ranking would loose precision.
* WIP implementation
* Cleanup implementation
* Install backedge rather than storing array reference
* Add diagnostics
* Add missing parameter to ResultFinderForTypeContext constructor
* Fix tests for correct fix-it language
* Change to solution without backedge, change lookup behavior
* Improve diagnostics for weak captures and captures under different names
* Remove ghosts of implementations past
* Address review comments
* Reorder member variable initialization
* Fix typos
* Exclude value types from explicit self requirements
* Add tests
* Add implementation for AST lookup
* Add tests
* Begin addressing review comments
* Re-enable AST scope lookup
* Add fixme
* Pull fix-its into a separate function
* Remove capturedSelfContext tracking from type property initializers
* Add const specifiers to arguments
* Address review comments
* Fix string literals
* Refactor implicit self diagnostics
* Add comment
* Remove trailing whitespace
* Add tests for capture list across multiple lines
* Add additional test
* Fix typo
* Remove use of ?: to fix linux build
* Remove second use of ?:
* Rework logic for finding nested self contexts
If return type is a function, it's possible to return a closure
which can have some of its arguments unused in the body e.g.
`let _: () -> ((Int) -> Void) = { return { } }`
In this case resulting closure has to use its only parameter or
explictly ignore it by declaring `_ in`.
Solutions passed to `diagnoseAmbiguityWithFixes` aren't filtered
so we need to remove all of the solutions with the score worse
than overall "best". Also logic has to account for some fixes being
"warnings".
