While looking at the places in swift repo where there are closures at the end of calls, but don't use the trailing closure syntax, I noticed that a lot of them are used for BenchmarkInfo initializers
BenchmarkInfo(
name: "AngryPhonebook.ASCII.Small",
runFunction: { angryPhonebook($0, ascii) },
tags: t,
setUpFunction: { blackHole(ascii) }),
This proposal would not change that. Even more reasons against this proposal.