Bad pointer dereference crash when using parameter pack

[theblixguy]

class Thing<T> {
  var value: T
  init(_ value: T) { self.value = value }

  func combineThings<each U>(head: Thing<T>, tail: repeat Thing<each U>) { 
    repeat (each tail).doSomething(each tail) { _ in }
  }

  func doSomething(_ value: AnyObject, closure: @escaping (T) -> Void) {}
}

This crashes on latest nightly (Swift version 5.11-dev (LLVM 82306b901067e3c, Swift cabb5e109fa373f)) with:

Archetype τ_2_0 not allowed in this context
Archetype generic signature: <τ_0_0, each τ_1_0, τ_2_0>
Context generic signature: <T, each U>

and further down it says

Program crashed: Bad pointer dereference at 0x0000000000000000

Similar crash on 5.9 too.

[AnthonyLatsis]

Reduced test case:

struct Thing<T> {
  func doSomething(_: (T) -> Void) {}
}

func test<each U>(_ thing: repeat Thing<each U>) {
  repeat (each thing).doSomething { x in }
}

Archetype τ_1_0 not allowed in this context
Archetype generic signature: <each τ_0_0, τ_1_0>
Context generic signature: <each U>