I wanted to answer with "because Swift's type checking is decidable", but that has changed (with SE-0142 and SE-0157) - allowing recursion. So, it is 'at least'

I wanted to answer with "because Swift's type checking is decidable", but that has changed (with SE-0142 and SE-0157) - allowing recursion. So, it is 'at least' undecidable now. https://forums.swift.org/t/swift-type-checking-is-undecidable/39024 https://forums.swift.org/t/swift-type-checking-is-undecidabl...