Provide an explicit iterator for SyntaxCollection #13112
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The default IndexingIterator for a custom collection is not suitable for subclasses that specialize the element type the way libSyntax does. Overriding it with a more specific iterator, even with something like covariant overrides, would not work because it the iterator is generic over its base collection, not its element type. Provide a custom iterator parameterized by the element type instead.
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@swift-ci please smoke test |
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I wouldn't say this is NFC, because it changes what the iterator type is, no? Regardless, this is how this was intended to work. LGTM. |
harlanhaskins
approved these changes
Nov 28, 2017
Before this patch, iterating over the syntax collection in a for-each loop wasn't possible. The only way clients would break is if they were relying on the default iterator type specifically being IndexingIterator. |
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Right, yes. But adding that functionality makes this an FC. 😉 |
CodaFi
changed the title
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Eh, I'm not willing to die on this hill. |
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CI Passed, I say merge. ⛴ |
maldahleh
pushed a commit
to maldahleh/swift
that referenced
this pull request
Oct 26, 2020
The default IndexingIterator for a custom collection is not suitable for subclasses that specialize the element type the way libSyntax does. Overriding it with a more specific iterator, even with something like covariant overrides, would not work because it the iterator is generic over its base collection, not its element type. Provide a custom iterator parameterized by the element type instead.
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The default IndexingIterator for a custom collection is not suitable for
subclasses that specialize the element type the way libSyntax does.
Overriding it with a more specific iterator, even with something like
covariant overrides, would not work because it the iterator is generic
over its base collection, not its element type.
Provide a custom iterator parameterized by the element type instead.
We discovered this while working with the libSyntax representation in Silt.