The introduction of forward-scan matching for trailing closures
(SE-0286) failed to account for unresolved member expressions,
sometimes causing a crash in SILGen. Fixes rdar://problem/67781123.
This approach, suggested by Xiaodi Wu, provides better source
compatibility for existing Swift code, by breaking ties in favor of the
existing Swift semantics. Each time the backward-scan rule is needed
(and differs from the forward-scan result), we will produce a warning
+ Fix-It to prepare for Swift 6 where the backward rule can be
removed.
My experiment to improve source compatibility by also performing a
backward scan removed the SE-0286 heuristic that skipped binding
the unlabeled trailing closure to a defaulted parameter when that
would fail. Reinstate that heuristic, which makes more existing code
work with the forward-scan behavior.
This makes my source-compatibility improvements a quality-of-implementation
Whenever we form a call that relies on the deprecated "backward" scan,
produce a warning to note the deprecation along with a Fix-It to label
the parameter appropriately (and suppress the warning). For example:
warning: backward matching of the unlabeled trailing closure is
deprecated; label the argument with 'g' to suppress this warning
trailingClosureEitherDirection { $0 * $1 }
^
(g: )
To better preserve source compatibility, teach the constraint
solver to try both the new forward scanning rule as well as the
backward scanning rule when matching a single, unlabeled trailing
closure. In the extreme case, where the unlabeled trailing closure
matches different parameters with the different rules, and yet both
produce a potential match, introduce a disjunction to explore both
possibilities.
Prefer solutions that involve forward scans to those that involve
backward scans, so we only use the backward scan as a fallback.
SE-0248 changes the backward-scan matching behavior for the unlabeled
trailing closure into a forward scan. In circumstances where this
could silently change the meaning of a call to a particular
function, i.e., when there are two defaulted closure parameters such
that a given closure to match either one of them, produce an warning
that describes the change in behavior. For example:
t4.swift:2:24: warning: since Swift 5.3, unlabeled trailing
closure argument matches parameter 'x' rather than parameter 'z'
trailingClosureSingle2 { $0 }
^
t4.swift:2:24: note: label the argument with 'z' to retain the
pre-Swift 5.3 behavior
trailingClosureSingle2 { $0 }
^
(z: )
t4.swift:2:24: note: label the argument with 'x' to silence this
warning for Swift 5.3 and newer
trailingClosureSingle2 { $0 }
^
(x: )
t4.swift:1:6: note: 'trailingClosureSingle2(x:y:z:)' contains
defaulted closure parameters 'x' and 'z'
func trailingClosureSingle2(x: (Int) -> Int = { $0 } , y: (Int) ->
Int = { $0 }, z: (Int) -> Int = { $0 }) {}
^ ~
This explains the (rare) case where SE-0286 silently changes the
meaning of a program, offering Fix-Its to either restore the
pre-SE-0286 behavior or silence the warning, as appropriate.
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.
Once the first argument for a variadic function-typed parameter has been
matched, allow an unlabeled trailing closure to match, rather than
banning all uses of the unlabeled trailing closure with variadic
parameters.
The "fuzzy" forward scan matching algorithm was only applied when there
was a single, unlabeled trailing closure, but was disabled in the
presence of multiple trailing closures. Extend the "fuzzy" match to
account for multiple trailing closures, by restricting the search for
"a later parameter that needs an argument" to stop when we find a
parameter that matches the first (labeled) trailing closure.
Introsuce a new "forward" algorithm for trailing closures where
the unlabeled trailing closure argument matches the next parameter in
the parameter list that can accept an unlabeled trailing closure.
The "can accept an unlabeled trailing closure" criteria looks at the
parameter itself. The parameter accepts an unlabeled trailing closure
if all of the following are true:
* The parameter is not 'inout'
* The adjusted type of the parameter (defined below) is a function type
The adjusted type of the parameter is the parameter's type as
declared, after performing two adjustments:
* If the parameter is an @autoclosure, use the result type of the
parameter's declared (function) type, before performing the second
adjustment.
* Remove all outer "optional" types.
For example, the following function illustrates both adjustments to
determine that the parameter "body" accepts an unlabeled trailing
closure:
func doSomething(body: @autoclosure () -> (((Int) -> String)?))
This is a source-breaking change. However, there is a "fuzzy" matching
rule that that addresses the source break we've observed in practice,
where a defaulted closure parameter precedes a non-defaulted closure
parameter:
func doSomethingElse(
onError: ((Error) -> Void)? = nil,
onCompletion: (Int) -> Void
) { }
doSomethingElse { x in
print(x)
}
With the existing "backward" scan rule, the trailing closure matches
onCompletion, and onError is given the default of "nil". With the
forward scanning rule, the trailing closure matches onError, and there
is no "onCompletion" argument, so the call fails.
The fuzzy matching rule proceeds as follows:
* if the call has a single, unlabeled trailing closure argument, and
* the parameter that would match the unlabeled trailing closure
argument has a default, and
* there are parameters *after* that parameter that require an argument
(i.e., they are not variadic and do not have a default argument)
then the forward scan skips this parameter and considers the next
parameter that could accept the unlabeled trailing closure.
Note that APIs like doSomethingElse(onError:onCompletion:) above
should probably be reworked to put the defaulted parameters at the
end, which works better with the forward scan and with multiple
trailing closures:
func doSomethingElseBetter(
onCompletion: (Int) -> Void,
onError: ((Error) -> Void)? = nil
) { }
doSomethingElseBetter { x in
print(x)
}
doSomethingElseBetter { x in
print(x)
} onError: { error in
throw error
}
A static reference to DynamicSelfType can only be written as an
implicit member expression where the contextual type is a
DynamicSelfType, ie, 'return .init(...)' in a static method
returning Self.
In this case, the base expression is not a statically-derived
metatype.
If the base value was 'self', we were allowing a reference to a
non-required initializer, because you're allowed to do this inside
another initializer.
But if you're in a static method, 'self.init' should obey the same
restrictions as 'foo.init' for any other metatype value 'foo'.
- All parts of the compiler now use ‘P1 & P2’ syntax
- The demangler and AST printer wrap the composition in parens if it is
in a metatype lookup
- IRGen mangles compositions differently
- “protocol<>” is now “swift.Any”
- “protocol<_TP1P,_TP1Q>” is now “_TP1P&_TP1Q”
- Tests cases are updated and added to test the new syntax and mangling
This commit defines the ‘Any’ keyword, implements parsing for composing
types with an infix ‘&’, and provides a fixit to convert ‘protocol<>’
- Updated tests & stdlib for new composition syntax
- Provide errors when compositions used in inheritance.
Any is treated as a contextual keyword. The name ‘Any’
is used emit the empty composition type. We have to
stop user declaring top level types spelled ‘Any’ too.
- Have DiagnosticEngine produce "aka" annotations for sugared types.
- Fix the "optional type '@lvalue C?' cannot be used as a boolean; test for '!= nil' instead"
diagnostic to stop printing @lvalue noise.
This addresses:
<rdar://problem/19036351> QoI: Print minimally-desugared 'aka' types like Clang does
Swift SVN r30587
This makes it clearer that expressions like "foo.myType.init()" are creating new objects, instead of invoking a weird-looking method. The last part of rdar://problem/21375845.
Swift SVN r29375
If P is a protocol, calling static methods or constructors
via values of type P.Protocol makes no sense, so let's prohibit
this.
Fixes <rdar://problem/21176676>.
Swift SVN r29338
If you want to make the parameter and argument label the same in
places where you don't get the argument label for free (i.e., the
first parameter of a function or a parameter of a subscript),
double-up the identifier:
func translate(dx dx: Int, dy: Int) { }
Make this a warning with Fix-Its to ease migration. Part of
rdar://problem/17218256.
Swift SVN r27715
The rule changes are as follows:
* All functions (introduced with the 'func' keyword) have argument
labels for arguments beyond the first, by default. Methods are no
longer special in this regard.
* The presence of a default argument no longer implies an argument
label.
The actual changes to the parser and printer are fairly simple; the
rest of the noise is updating the standard library, overlays, tests,
etc.
With the standard library, this change is intended to be API neutral:
I've added/removed #'s and _'s as appropriate to keep the user
interface the same. If we want to separately consider using argument
labels for more free functions now that the defaults in the language
have shifted, we can tackle that separately.
Fixes rdar://problem/17218256.
Swift SVN r27704
func a(b: Int = 0) {}
let c = a // should be (b: Int) -> Void, not (b: Int = 0) -> Void
Fixes crash suite #23.
rdar://problem/18232797
Swift SVN r24747
Most tests were using %swift or similar substitutions, which did not
include the target triple and SDK. The driver was defaulting to the
host OS. Thus, we could not run the tests when the standard library was
not built for OS X.
Swift SVN r24504
attribute is a "modifier" of a decl, not an "attribute" and thus shouldn't
be spelt with an @ sign. Teach the parser to parse "@foo" but reject it with
a nice diagnostic and a fixit if "foo" is a decl modifier.
Move 'dynamic' over to this (since it simplifies some code), and switch the
@optional and @required attributes to be declmodifiers (eliminating their @'s).
Swift SVN r19787
We had our transition path, and now it's time to kill it because it's
causing problems <rdar://problem/16672558>.
Amusing note: the SILGen test change is actually an improvement. We
weren't rebinding self when performing initializer delegation with the
separated call syntax.
Swift SVN r16707
We are removing this syntax. To stage the move, first error with
Fix-Its to rewrite to the keyword-argument syntax. In a week or so,
we'll remove all of the code supporting the "separated" call syntax.
Swift SVN r15833
An arbitrary value of class metatype cannot be used to construct an
object, because there's no guarantee that a given subclass will
provide that initializer.
Swift SVN r14175
