最近の opaque & existential type 関連の Proposal を洗い出してみた。

https://github.com/apple/swift-evolution/blob/main/proposals/0309-unlock-existential-types-for-all-protocols.md
https://github.com/apple/swift-evolution/blob/main/proposals/0328-structural-opaque-result-types.md
https://github.com/apple/swift-evolution/blob/main/proposals/0335-existential-any.md
https://github.com/apple/swift-evolution/blob/main/proposals/0341-opaque-parameters.md
https://github.com/apple/swift-evolution/blob/main/proposals/0346-light-weight-same-type-syntax.md
https://github.com/apple/swift-evolution/blob/main/proposals/0352-implicit-open-existentials.md
https://github.com/apple/swift-evolution/blob/main/proposals/0353-constrained-existential-types.md