Sequence/Iterator conformance broken in 5.7 #60514
Comments
MaxDesiatov
added
bug
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@hborla I have a feeling this can be related to primary associated type changes that landed in 5.7. Since you worked on those, would you have a moment to give some guidance on what caused the issue? Thanks! |
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@MaxDesiatov the type checking of @xedin I remember there was another ambiguity related to that change. Any ideas here? |
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I've also tried adding a constraint on public protocol VectorSectionReader: Sequence
where Element == Result<Item, Error>, Iterator == VectorSectionIterator<Self> {
// ...
}That makes it complain about circular references between |
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The issue here is that |
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@MaxDesiatov Adding that same-type requirement on the extension fixes it: extension VectorSectionReader where Iterator == VectorSectionIterator<Self> {
__consuming public func makeIterator() -> VectorSectionIterator<Self> {
VectorSectionIterator(reader: self, count: count)
}
public func collect() throws -> [Item] {
var items: [Item] = []
items.reserveCapacity(Int(count))
for result in self {
try items.append(result.get())
}
return items
}
} |
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Perfect, thank you! I guess I can keep this open as a regression? |
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@MaxDesiatov Does it make sense for @hborla |
In this case default I'm not the original author of the code, but I'll let @kateinoigakukun correct me if I'm wrong: the whole purpose of |
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@MaxDesiatov as far as I remember, Max understands my intention for the code correctly. So it seems ok with Holly's suggestion in our case. |
…ntext
Prefer an overload of `makeIterator` that satisfies
`Sequence#makeIterator` requirement when `.makeIterator()`
is implicitly injected after sequence expression in `for-in`
loop context.
This helps to avoid issues related to conditional conformances
to `Sequence` that add `makeIterator` preferred by overloading
rules that could change behavior i.e.:
```swift
extension Array where Element == Double {
func makeIterator() -> Array<Int>.Iterator {
return [1, 2, 3].makeIterator()
}
}
for i in [4.0, 5.0, 6.0] {
print(i)
}
```
`makeIterator` declared in the `Array` extension is not a witness
to `Sequence#makeIterator` and shouldn't be used because that would
change runtime behavior.
Resolves: apple#60514
Resolves: apple#60958
…ntext
Prefer an overload of `makeIterator` that satisfies
`Sequence#makeIterator` requirement when `.makeIterator()`
is implicitly injected after sequence expression in `for-in`
loop context.
This helps to avoid issues related to conditional conformances
to `Sequence` that add `makeIterator` preferred by overloading
rules that could change behavior i.e.:
```swift
extension Array where Element == Double {
func makeIterator() -> Array<Int>.Iterator {
return [1, 2, 3].makeIterator()
}
}
for i in [4.0, 5.0, 6.0] {
print(i)
}
```
`makeIterator` declared in the `Array` extension is not a witness
to `Sequence#makeIterator` and shouldn't be used because that would
change runtime behavior.
Resolves: apple#60514
Resolves: apple#60958
Describe the bug
Code utilizing
SequenceandIteratorprotocols that worked in previous versions of Swift no longer type-checks in 5.7 snapshots.Steps To Reproduce
Try to build WasmTransformer with Xcode 14.0 beta 5.
Expected behavior
This code type-checks and builds as it did Swift 5.5/5.6
Screenshots
Environment (please fill out the following information)
swiftlang/swift:nightly-5.7-focalimage and6fa8c6b08e85hash.Additional context
Here's the code snippet (not self-contained, but I hope it helps to pinpoint the issue) that causes these new errors:
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