Incorrect generic signature minimization causes failure in concrete equivalence class splitting

[slavapestov]

Reduced from https://forums.swift.org/t/requirement-machine-failure/64235/3. The problem is the generic signature of foo() below.

The second same-type requirement is bogus and should have been minimized away:

Splitting concrete equivalence classes did not reach fixed point after 2 attempts.
Last attempt produced these requirements:
conforms_to: T BidirectionalPattern
same_type: T.[Pattern]Match.[PatternMatch]Searched Data
same_type: T.[Pattern]Match.[PatternMatch]Searched.[BidirectionalPattern]Reversed.[Collection]SubSequence T.[Pattern]Match.[PatternMatch]Searched.[BidirectionalPattern]Reversed.[Pattern]SubSequencePattern
Requirement machine for <τ_0_0 where τ_0_0 : BidirectionalPattern, τ_0_0.Match.Searched == Data, τ_0_0.Match.Searched.Reversed.SubSequence == τ_0_0.Match.Searched.Reversed.SubSequencePattern>

import Foundation

protocol BidirectionalPattern: Pattern where Searchable: SearchableBidirectionalCollection {
  associatedtype Reversed: Pattern where Reversed.Searchable == ReversedCollection<Searchable>
}

protocol SearchableBidirectionalCollection: BidirectionalCollection, BidirectionalPattern, SearchableCollection where SubSequence: SearchableBidirectionalCollection {
}

protocol SearchableCollection: Collection, Pattern where Element: Equatable, Searchable == Self, SubSequence: SearchableCollection {}

protocol Pattern {
  typealias Searchable = Match.Searched

  associatedtype Match: PatternMatch

  associatedtype SubSequencePattern: Pattern where SubSequencePattern.Searchable == Searchable.SubSequence
}

protocol PatternMatch {
  associatedtype Searched: SearchableCollection
}

extension ReversedCollection: Pattern, SearchableCollection where Base: SearchableCollection {
  typealias Match = AtomicPatternMatch<ReversedCollection<Base>>
  typealias SubSequencePattern = Slice<ReversedCollection<Base>>
}

extension ReversedCollection: BidirectionalPattern, SearchableBidirectionalCollection where Base: SearchableBidirectionalCollection {
  typealias Reversed = ReversedCollection<Self>
}

struct AtomicPatternMatch<Searched>: PatternMatch where Searched: SearchableCollection {}

extension Data: SearchableBidirectionalCollection {
  typealias Reversed = ReversedCollection<Data>
  typealias Match = AtomicPatternMatch<Data>
  typealias SubSequencePattern = Data

}

extension Slice: Pattern, SearchableCollection where Base: SearchableCollection {
  typealias Match = AtomicPatternMatch<Slice<Base>>
  typealias SubSequencePattern = Slice<Base>
}

extension Slice: BidirectionalPattern, SearchableBidirectionalCollection where Base: SearchableBidirectionalCollection {
  typealias Reversed = ReversedCollection<Self>
}

func foo<T: BidirectionalPattern>(_: T) where T.Match.Searched == Data {}