[5.9] ClosureLifetimeFixup: Remove copy of borrowed move-only nonescaping captures when possible. #66779
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…aptures when possible. SILGen introduces a copy of the capture, because the semantics of escaping partial_apply's requires the closure to take ownership of the parameters. We don't know when a closure is strictly nonescaping or its final lifetime until ClosureLifetimeFixup runs, but that replaces the consume of the copy with a borrow of the copy normally, hoping later passes fix it up. We can't wait that long for move-only types, which can't be copied, so try to remove the copy up front when the copy lives long enough and has no interfering uses other than the partial_apply. rdar://110137169
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@swift-ci Please test |
tbkka
approved these changes
Jun 20, 2023
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Issue: rdar://110137169
• Explanation: Fixes a bug where attempting to capture a noncopyable value in a nonescaping closure would be incorrectly rejected.
• Scope of Issue: Fixes an incorrect diagnostic on correct code.
• Origination: Noncopyable types feature work
• Risk: Low. The change is focused to only affect noncopyable types, so existing code won't be affected.
• Reviewed By: @atrick and @gottesmm
• Automated Testing: Swift CI
• Dependencies: None
• Builder Impact: Not applicable
• Directions for QE: None