import 盛り込まれております https://github.com/swiftlang/swift-syntax/blob/6df106db45da4536a3c9f8cd2a21918999127924/Tests/SwiftParserTest/translated/ModuleSelectorTests.swift#L24-L41 プロポーザルだとGrammarの項にさらっと書かれてるだけですね

swift-syntax/Tests/SwiftParserTest/translated/ModuleSelectorTests.s...

A set of Swift libraries for parsing, inspecting, generating, and transforming Swift source code. - swiftlang/swift-syntax

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