Are `switch` statements over `String` ever optimized to a hash table lookup?

Karl · January 28, 2020, 1:57am

Check out StringSwitch.swift, specifically _findStringSwitchCaseWithCache. The cache is a Dictionary, so it's a hash-table lookup, but it only appears to apply to strings.

It gets used in SILOptimizer: swift/ObjectOutliner.cpp at 291364b2f1b81c100b155de900494780ed79bded · apple/swift · GitHub

EDIT: It's only used for synthesised RawRepresentable conformances. There is a PR to expand this.