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[SR-15061] EnumeratedSequence underestimatedCount does not forward the base enumeratedCount #57388

swift-ci opened this issue Aug 13, 2021 · 1 comment


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swift-ci commented Aug 13, 2021

Previous ID SR-15061
Radar rdar://problem/81907273
Original Reporter laclouis5 (JIRA User)
Type Bug
Additional Detail from JIRA
Votes 0
Component/s Standard Library
Labels Bug
Assignee None
Priority Medium

md5: e03ba826acc0bd91edbf5d0b7b77aee4

Issue Description:

All lazy adaptors forward the underestimatedCount property of Sequences excepted EnumeratedSequence:

let array = [1, 2, 3, 4, 5]
let enumerated = array.enumerated()
print(enumerated.underestimatedCount)  // 0

Is this expected behavior? Does it create unnecessary reallocations in such code:

// array: some array 
let result = Array(array.enumerated().map { $0 })  // this Sequence underestimatedCount is 0
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typesanitizer commented Aug 13, 2021

@swift-ci create

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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