[5.7] Runtime Casting for Extended Existentials #59511
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
Implement casting to and from extended existentials. This is done by slightly generalizing the conditional conformances checking infrastructure. Unfortunately, casts for reference types and metatypes are unsound because IRGen is peepholing all non-opaque existential conversions with a helper. I’ll disable that in a follow-up. rdar://92197049
The fix here is two-fold: 1) Teach SILGen that it cannot use the scalar casting paths for extended existentials 2) Teach the runtime casting entrypoint to unwrap as much metatype structure as possible before arriving at a 'Self' type bound for the requirement checking paths. The code here mirrors the destructuring check we're doing in remote mirrors. rdar://95166916
Return a NULL demangle tree instead of crashing. When an unconditional runtime cast fails, it's going to crash anyways, but this way it prints a better description (though not great) than the unreachable's message here.
Ensure the last node after all of the destructuring really is a dependent generic param type. If it isn't, something has gone horribly wrong.
|
@swift-ci test |
tbkka
reviewed
Jun 17, 2022
| @@ -0,0 +1,114 @@ | |||
| // ParameterizedExistentials.swift - Tests for class constant casts w/ Obj-C | |||
There was a problem hiding this comment.
Does the summary here need to be updated?
| expectEqual(a.value, b.value) | ||
| let c = GenericHolder(value: 5) as? any Holder<Int> | ||
| expectNotNil(c) | ||
| let d = GenericHolder(value: 5) as? any Holder<String> |
There was a problem hiding this comment.
I see you've tried to exercise as, as!, and as?. Some of the other casting tests also use this function, which seems to reliably defeat compiler optimizations and forces use of the most-general casting path. It may not be needed for this case, since these casts don't seem to have an alternate runtime path at current.
fileprivate func runtimeCast<From, To> (_ x: From, to: To.Type) -> To? {
return x as? To
}
| @@ -1695,10 +1695,56 @@ tryCastUnwrappingExistentialSource( | |||
| return tryCast(destLocation, destType, | |||
| srcInnerValue, srcInnerType, | |||
| destFailureType, srcFailureType, | |||
| takeOnSuccess & (srcInnerValue == srcValue), | |||
| takeOnSuccess && (srcInnerValue == srcValue), | |||
| srcFailureType = srcInnerType; | ||
| return tryCast(destLocation, destType, srcInnerValue, srcInnerType, | ||
| destFailureType, srcFailureType, | ||
| takeOnSuccess & (srcInnerValue == srcValue), mayDeferChecks); |
There was a problem hiding this comment.
It should be! @rjmccall caught this the first time around. I'll patch this out on main.
| return tryCastToObjectiveCClass; | ||
| case MetadataKind::ExistentialMetatype: | ||
| return tryCastToExistentialMetatype; | ||
| return tryCastToExistentialMetatype; |
There was a problem hiding this comment.
Thank you for fixing whitespace.
tbkka
approved these changes
Jun 17, 2022
AnthonyLatsis
added
🍒 release cherry pick
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.
Cherry pick of #59455 and #59507
Implement the runtime entry points for casting to and from constrained existential types.
rdar://92197049