22064783: Swift 2.0b4: Mutually recursive protocols cause swiftc to infinite loop and crash

[openradar-mirror]

Description

Summary:
So, y’all use recursion too!

Steps to Reproduce:
This code:
protocol A {
typealias O : B
}
protocol B {
typealias O : A
}

Expected Results:
should not crash swiftc

Actual Results:
but totally does:
510 swift 0x0000000103a1c8bf swift::ArchetypeBuilder::addConformanceRequirement(swift::ArchetypeBuilder::PotentialArchetype_, swift::ProtocolDecl_, swift::RequirementSource) + 655
511 swift 0x0000000103a1c8bf swift::ArchetypeBuilder::addConformanceRequirement(swift::ArchetypeBuilder::PotentialArchetype_, swift::ProtocolDecl_, swift::RequirementSource) + 655

Regression:
N/A

Notes:
N/A

Product Version: Xcode-beta (7A165t)
Created: 2015-07-30 01:52:25.289300
Originated: 2015-07-29T21:52:00
Open Radar Link: http://www.openradar.me/22064783