Don't reserveCapacity in append(contentsOf:), it breaks API guarantees of asymptotic complexity (swiftlang#65927)

Catfish-Man · web-flow · commit e342ac4ee322 · 2023-05-19T12:13:55.000-07:00
Don't reserveCapacity in append(contentsOf:), it breaks API guarantees of asymptotic complexity. Fixes rdar://109577273
diff --git a/stdlib/public/core/RangeReplaceableCollection.swift b/stdlib/public/core/RangeReplaceableCollection.swift
@@ -459,8 +459,6 @@ extension RangeReplaceableCollection {
     }
       
     if done == nil {
-      let approximateCapacity = self.count + newElements.underestimatedCount
-      self.reserveCapacity(approximateCapacity)
       for element in newElements {
         append(element)
       }

Original file line number	Diff line number	Diff line change
`@@ -459,8 +459,6 @@ extension RangeReplaceableCollection {`
`459`	`459`	`}`
`460`	`460`
`461`	`461`	`if done == nil {`
`462`		`- let approximateCapacity = self.count + newElements.underestimatedCount`
`463`		`- self.reserveCapacity(approximateCapacity)`
`464`	`462`	`for element in newElements {`
`465`	`463`	`append(element)`
`466`	`464`	`}`