Add an educational note explaining SE-0286 changes #33119
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
owenv
commented
Jul 25, 2020
|
|
||
| In Swift, calling a function with one or more trailing closure arguments requires the label of the first trailing closure argument to be omitted. As a result, the compiler must consider additional context when determining which function parameter the trailing closure should satisfy. | ||
|
|
||
| Before Swift 5.3, the compiler used a backward scanning rule to match a trailing closure to a function parameter. Starting from the end of the parameter list, it moved backwards until finding a parameter compatible with trailing closures. This could sometimes lead to unexpected behavior. Consider the following example: |
There was a problem hiding this comment.
This explanation is a little vague, but I think that's OK since it describes the old behavior
There was a problem hiding this comment.
Maybe replace compatible with trailing closures with which could accept a trailing closure argument i.e. function type, generic parameter, 'Any' type?
|
Thanks @benrimmington! |
owenv
force-pushed
the
closure-matching-note
branch
from
5d79f83 to
cee71ae
Compare
This comment has been minimized.
This comment has been minimized.
xedin
approved these changes
Jul 27, 2020
|
|
||
| In Swift, calling a function with one or more trailing closure arguments requires the label of the first trailing closure argument to be omitted. As a result, the compiler must consider additional context when determining which function parameter the trailing closure should satisfy. | ||
|
|
||
| Before Swift 5.3, the compiler used a backward scanning rule to match a trailing closure to a function parameter. Starting from the end of the parameter list, it moved backwards until finding a parameter compatible with trailing closures. This could sometimes lead to unexpected behavior. Consider the following example: |
There was a problem hiding this comment.
Maybe replace compatible with trailing closures with which could accept a trailing closure argument i.e. function type, generic parameter, 'Any' type?
Apply suggestions from code review Co-authored-by: Ben Rimmington <[email protected]> Reword explanation of pre-5.3 behavior Associate SE-0286 note with warning diagnostic
owenv
force-pushed
the
closure-matching-note
branch
from
a017a58 to
bacc96b
Compare
|
@swift-ci smoke test |
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.
Some of this is copied verbatim from the proposal, but IMO it's important to have some documentation of this change beyond the SE proposal to communicate the expected impact.
If and when SE-0286 is accepted, I'll associate this note with whatever the final set of diagnostics is and hopefully cherrypick to the 5.3 branch.