この辺りか。 https://github.com/apple/swift/commits/7764f64cf87b51d59eddd41e0cd6b13bd0cf5da3/stdlib/core/Assert.swift.gyb

8:37 AM

https://github.com/apple/swift/commit/7764f64cf87b51d59eddd41e0cd6b13bd0cf5da3#diff-3de648a1087356b522601f7eb52ba304