Add regression tests for rdar://116434843 and #59772

Author: slavapestov

test/Generics/rdar116434843.swift

@@ -0,0 +1,26 @@
+// RUN: %target-typecheck-verify-swift
+
+protocol P {}
+
+struct X: P {}
+
+protocol Q {
+  typealias A = X
+}
+
+protocol R {
+  associatedtype A: Q
+  associatedtype B: P
+}
+
+protocol S {}
+
+extension S where Self: R {
+  typealias B = Self.A.A
+}
+
+typealias T<A: Q> = G<A>.B
+
+struct G<A: Q>: R, S {
+  typealias A = A
+}

validation-test/compiler_crashers_2_fixed/issue-59772.swift

@@ -0,0 +1,97 @@
+// RUN: %target-swift-frontend -emit-ir -primary-file %s
+
+private typealias Word = UInt
+
+/// Returns the offset at which the `i`th bit can be found in an array of
+/// `Word`s.
+private func wordOffset(ofBit i: Int) -> Int {
+  precondition(i >= 0)
+  return i / Word.bitWidth
+}
+
+/// Returns a mask that isolates the `i`th bit within its `Word` in an array of
+/// `Word`s.
+private func wordMask(ofBit i: Int) -> Word {
+  precondition(i >= 0)
+  return (1 as Word) << (i % Word.bitWidth)
+}
+
+/// An adapter that presents a base instance of `S` as a sequence of bits packed
+/// into `Word`, where `true` and `false` in the base are represented as `1` and
+/// `0` bits in an element of `self`, respectively.
+private struct PackedIntoWords<S: Sequence>: Sequence where S.Element == Bool {
+  /// The iteration state of a traversal of a `PackedIntoWords`.
+  struct Iterator: IteratorProtocol {
+    var base: S.Iterator
+
+    mutating func next() -> Word? {
+      guard let b = base.next() else { return nil }
+      var r: Word = b ? 1 : 0
+      for i in 1..<Word.bitWidth {
+        guard let b = base.next() else { return r }
+        if b { r |= wordMask(ofBit: i) }
+      }
+      return r
+    }
+  }
+  /// Returns a new iterator over `self`.
+  func makeIterator() -> Iterator { Iterator(base: base.makeIterator()) }
+
+  /// Returns a number no greater than the number of elements in `self`.
+  var underestimatedCount: Int {
+    (base.underestimatedCount + Word.bitWidth - 1) / Word.bitWidth
+  }
+
+  /// The underlying sequence of `Bool`.
+  let base: S
+
+  init(_ base: S) { self.base = base }
+}
+
+struct Bits<Base: Sequence>: Sequence
+  where Base.Element: FixedWidthInteger
+{
+  public var base: Base
+  typealias Element = Bool
+
+  func makeIterator() -> Iterator { Iterator(base: base.makeIterator()) }
+
+  struct Iterator: IteratorProtocol {
+    typealias Element = Bool
+
+    var base: Base.Iterator
+    var buffer: Base.Element.Magnitude = 0
+
+    mutating func next() -> Bool? {
+      let r = buffer & 0x1 != 0
+      buffer >>= 1
+      if buffer != 0 { return r }
+      guard let b = base.next() else { return nil }
+      let r1 = b & 0x1 != 0
+      buffer = Base.Element.Magnitude(truncatingIfNeeded: b)
+      buffer >>= 1
+      buffer |= 1 << (Base.Element.bitWidth - 1)
+      return r1
+    }
+  }
+}
+
+extension Bits: Equatable where Base: Equatable {}
+extension Bits: Hashable where Base: Hashable {}
+
+extension Bits: RandomAccessCollection, BidirectionalCollection, Collection
+  where Base: RandomAccessCollection
+{
+//  typealias Index = Int
+  var startIndex: Int { return 0 }
+  var endIndex: Int { return base.count * Base.Element.bitWidth }
+
+  fileprivate func baseIndex(_ i: Int) -> Base.Index {
+    base.index(base.startIndex, offsetBy: i / Base.Element.bitWidth)
+  }
+
+  subscript(i: Int) -> Bool {
+    base[baseIndex(i)] & (1 << (i % Base.Element.bitWidth)) != 0
+  }
+}
+