Location
https://docs.swift.org/swift-book/documentation/the-swift-programming-language/lexicalstructure#Keywords-and-Punctuation
Description
#unavailable is given in the Grammar of an availability condition subsection of the Statements subsection of the Summary of the Grammar section but is not identified in the keywords that begin with a number sign (#).
Correction
Append #unavailable to the list of keywords that begin with a number sign (#).