[5.7] Fix Repeat off-by-one error#536

hamishknight merged 2 commits intoswiftlang:swift/release/5.7swiftlang/swift-experimental-string-processing:swift/release/5.7from

hamishknight:one-more-5.7hamishknight/swift-experimental-string-processing:one-more-5.7Copy head branch name to clipboard