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The grammar here would only allow `~P` on the final element of a list but it's allowed on any of the elements (eg, `struct S: ~Copyable, ~Escapable`).
amartini51
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Mar 13, 2026
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amartini51
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amartini51
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Yes, this looks like an oversight when updating the grammar. I agree with the summary in the PR — without this change, ~P is only allowed on the last element of the list, because that's the only time the left-hand production is used.
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The grammar here would only allow
~Pon the final element of a list but it's allowed on any of the elements (eg,struct S: ~Copyable, ~Escapable).Another way to see the bug: notice how the grammar only allows a comma after a type-identifier's that may not have a
~.