Add regression test for rdar://problem/90506460

Author: slavapestov

test/Generics/rdar90506460.swift

@@ -0,0 +1,27 @@
+// RUN: %target-swift-frontend -typecheck %s -debug-generic-signatures -requirement-machine-protocol-signatures=on 2>&1 | %FileCheck %s
+
+// CHECK-LABEL: .P1@
+// CHECK-NEXT: Requirement signature: <Self where Self == Self.[P1]A.[P2]C, Self.[P1]A : P3, Self.[P1]B : P4, Self.[P1]A.[P2]C == Self.[P1]B.[P2]C>
+public protocol P1 {
+  associatedtype A: P3 where A.C == Self
+  associatedtype B: P4 where B.C == Self
+}
+
+// CHECK-LABEL: .P2@
+// CHECK-NEXT: Requirement signature: <Self where Self : CaseIterable, Self : Hashable, Self : RawRepresentable, Self.[P2]C : P1, Self.[P2]D : P5, Self.[RawRepresentable]RawValue == String>
+public protocol P2: Hashable, RawRepresentable, CaseIterable where RawValue == String {
+  associatedtype C: P1
+  associatedtype D: P5
+}
+
+// CHECK-LABEL: .P3@
+// CHECK-NEXT: Requirement signature: <Self where Self : P2>
+public protocol P3: P2 {}
+
+// CHECK-LABEL: .P4@
+// CHECK-NEXT: Requirement signature: <Self where Self : P2>
+public protocol P4: P2 {}
+
+// CHECK-LABEL: .P5@
+// CHECK-NEXT: Requirement signature: <Self where Self : CaseIterable, Self : Hashable, Self : RawRepresentable, Self.[RawRepresentable]RawValue == String>
+public protocol P5: Hashable, RawRepresentable, CaseIterable where RawValue == String {}