AST: Fix a problem with the protocol order #80213
Merged
+66
−3
Conversation
This file contains 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
tshortli
approved these changes
Mar 21, 2025
slavapestov
force-pushed
the
protocol-order-fix
branch
2 times, most recently
from
5c97d9c to
2dc2cd0
Compare
The last step in building a generic signature is to sort the requirements. Requirements are sorted by comparing their subject types. If two requirements have the same subject type, which can only happen with conformance requirements, we break the tie by comparing protocol declarations. We compare protocol declarations using TypeDecl::compare(), which is a shortlex order on the components of the fully qualified name of a protocol (eg, Swift.Sequence, etc.) While this order is part of the ABI, it has not been updated over the years for several important changes: - It did not handle module aliases; if we import a module via an alias, we should use the real module name to compare protocols, and not the aliased name. This produced inconsistent results if the same module was imported under different names, which can happen with module interface files that use module aliases. - It did not handle the -module-abi-name flag. Changing the ABI name of a module changes how we mangle protocol names, and the order should match the mangling. This change fixes the first case only. The second requires more careful staging, because of _Concurrency and CompilerSwiftSyntax. Fixes rdar://147441890.
If a protocol was moved from one module to another, we need to continue using the old module name when comparing it against other protocols.
slavapestov
force-pushed
the
protocol-order-fix
branch
from
2dc2cd0 to
a7d2b24
Compare
|
@swift-ci Please test |
|
@swift-ci Please test source compatibility |
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 last step in building a generic signature is to sort the requirements. Requirements are sorted by comparing their subject types. If two requirements have the same subject type, which can only happen with conformance requirements, we break the tie by comparing protocol declarations.
We compare protocol declarations using TypeDecl::compare(), which is a shortlex order on the components of the fully qualified name of a protocol (eg, Swift.Sequence, etc.)
Ultimately, the protocol order determines mangled symbol names, the order of witness table arguments in the calling convention, the layout of existentials, and so on. While this order is part of the ABI, it has not been updated over the years for several important changes:
It did not handle module aliases; if we import a module via an alias, we should use the real module name to compare protocols, and not the aliased name. This produced inconsistent results if the same module was imported under different names, which can happen with module interface files that use module aliases.
It did not handle the
-module-abi-nameflag. Changing the ABI name of a module changes how we mangle protocol names, and the order should match the mangling.It did not use the original module name specified in the
@_originallyDefinedInflag, so moving a protocol between modules would change its position in the order.This PR fixes 1) and 3), but not 2).
Fixes rdar://147441890.