[Casting] Make more casts look inside __SwiftValue
#68952
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The following sequence of casts would previously succeed
```
struct S {}
let s = S() as AnyObject
s as? NSObject
```
The final cast here should fail, since `S` clearly is not a
subclass of NSObject. But it would previously succeed because
the `as AnyObject` would package the struct into an ObjC-compatible
`__SwiftValue` class. This latter is an NSObject subclass.
This bug was fixed in the main `swift_dynamicCast` runtime function
some time ago, but not in the `swift_dynamicCastObjCClass` which
is chosen by IRGen to optimize casts to ObjC class types.
This PR changes the latter to test for `__SwiftValue` and fall
back to the former in that case in order to get the correct
handling. Falling back to `swift_dynamicCast` also ensures that
the contents of the `__SwiftValue` are correctly unwrapped/bridged/etc
as necessary to fully support Swift casting semantics.
Resolves: rdar://111422725
TODO: I've left an XFAILed test here about the behavior of `type(of:)`
with `__SwiftValue` boxes.
|
@swift-ci Please test |
mikeash
approved these changes
Oct 4, 2023
|
@swift-ci Please test |
1 similar comment
|
@swift-ci Please test |
tbkka
added a commit
to tbkka/swift
that referenced
this pull request
Jan 18, 2024
…alue Turns out that our Obj-C bridging relies on this inconsistent behavior, so it can quite likely never be actually fixed.
tbkka
added a commit
that referenced
this pull request
Feb 2, 2024
Revert #68952 [Casting] Make more casts look inside __SwiftValue
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The following sequence of casts would previously succeed
The final cast here should fail, since
Sclearly is not a subclass of NSObject. But it would previously succeed because theas AnyObjectwould package the struct into an ObjC-compatible__SwiftValueclass. This latter is an NSObject subclass.This bug was fixed in the main
swift_dynamicCastruntime function some time ago, but not in theswift_dynamicCastObjCClasswhich is chosen by IRGen to optimize casts to ObjC class types. This PR changes the latter to test for__SwiftValueand fall back to the former in that case in order to get the correct handling. Falling back toswift_dynamicCastalso ensures that the contents of the__SwiftValueare correctly unwrapped/bridged/etc as necessary to fully support Swift casting semantics.Resolves: rdar://111422725
TODO: I've left an XFAILed test here about the behavior of
type(of:)with__SwiftValueboxes.