swift-format fails to parse valid swift code

[rauhul]

The following snippet fails to parse in swift-format but swiftc is able to compile it:

func foo<E: Error, T>(a: T, b: T, body: (T, T) throws(E) -> T) throws(E) -> T {
  try body(a, b)
}

struct S: Error { }

let x = try foo(a: 0, b: 1) { a, b throws(S) in 2 }
print(x)

repro:

# compile
$ xcrun -toolchain org.swift.59202405011a swiftc test.swift
$ ./test
2

# format
$ xcrun -toolchain org.swift.59202405011a swift-format format test.swift
/Users/rauhul/Desktop/test.swift:7:32: error: unexpected code ', b throws(S) in 2' in closure

[ahoppen]

Synced to Apple’s issue tracker as rdar://127750606

[allevato]

This code is using typed throws, which isn't supported by any released Xcode compiler that I'm aware of (it's still an experimental feature last time I checked). Do the open-source builds enable it by default?

Since we just use swift-syntax to parse, the error is coming out of there. We might need to provide a command line flag to pass experimental features through to swift-syntax's parser if we want to support pre-release syntax.

[bnbarham]

Typed throws isn't experimental in main or 6.0, I assume this is just a swift-syntax parsing bug - will move to there.

[rauhul]

Thanks for fixing this!