DocC cannot generate documentation for tuple containing multiple parameter packs.

[JessyCatterwaul]

Description

Here is the simplest example I've been able to come up with:

public func function<each Element0, each Element1>(
  _: (repeat (each Element0, each Element1))
) { }

---

You need that for the following kinds of stuff:

/// A tuple of pairs built out of two underlying tuples.
///
/// - Note: Unlike `zip` for sequences, these two tuples are required to have the same count.
@_documentation(visibility: private) // DocC can't cope with this signature.
@inlinable public func zip<each Element0, each Element1>(
  _ element0: (repeat each Element0),
  _ element1: (repeat each Element1)
) -> (repeat (each Element0, each Element1)) {
  (repeat (each element0, each element1))
}

/// Equate tuples of tuples.
///
/// Tuples can't be considered `Equatable`,
/// so just using a version of `==` that compares parameters packs of `Equatables` is not adequate.
@_documentation(visibility: private) // DocC can't cope with this signature.
@inlinable public func == <each Element0: Equatable, each Element1: Equatable>(
  _ element0: (repeat (each Element0, each Element1)),
  _ element1: (repeat (each Element0, each Element1))
) -> Bool {
  for elements in repeat (each element0, each element1) {
    guard elements.0 == elements.1 else { return false }
  }
  return true
}

Checklist

• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue.

Expected Behavior

I don't have to add @_documentation(visibility: private) to such code, and can document it! 📜

Actual behavior

Error: dataCorrupted(Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "symbols", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "swiftGenerics", intValue: nil), CodingKeys(stringValue: "constraints", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "kind", intValue: nil)], debugDescription: "Cannot initialize Kind from invalid String value sameShape", underlyingError: nil))
Command CompileDocumentation failed with a nonzero exit code

Steps To Reproduce

No response

Swift-DocC Version Information

Tip of main: 081ad56

Swift Compiler Version Information

swift-driver version: 1.112.3 Apple Swift version 6.0 (swiftlang-6.0.0.6.8 clang-1600.0.23.1)

[aim2120]

Experiencing the same problem in my project.

Triggering code:

public func MapPack<each V, each V2>(_ value: repeat each V, transform: repeat (each V) -> (each V2)) -> (repeat each V2) {
    (repeat (each transform)(each value))
}

Error:

Error: dataCorrupted(Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "symbols", intValue: nil), _JSONKey(stringValue: "Index 1", intValue: 1), CodingKeys(stringValue: "swiftGenerics", intValue: nil), CodingKeys(stringValue: "constraints", intValue: nil), _JSONKey(stringValue: "Index 0", intValue: 0), CodingKeys(stringValue: "kind", intValue: nil)], debugDescription: "Cannot initialize Kind from invalid String value sameShape", underlyingError: nil))
Command CompileDocumentation failed with a nonzero exit code

Swift:

swift-driver version: 1.115 Apple Swift version 6.0.2 (swiftlang-6.0.2.1.2 clang-1600.0.26.4)
Target: arm64-apple-macosx14.0

Xcode:

Xcode 16.1
Build version 16B40