REPLで:type lookupだと型の情報が出るのに、使おうとするとunresolved identifierになる

$ docker run --privileged -it --rm norionomura/swift:40 swift -I/usr/lib/swift/clang/include Welcome to Swift version 4.0 (swift-4.0-RELEASE). Type :help for assistance. 1> import Foundation 2> :type lookup DBL_DECIMAL_DIG var DBL_DECIMAL_DIG: Swift.Int32 { get {} } 2> print(DBL_DECIMAL_DIG) error: repl.swift:2:7: error: use of unresolved identifier 'DBL_DECIMAL_DIG' print(DBL_DECIMAL_DIG) ^~~~~~~~~~~~~~~

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