Add a Compiler Crasher

The problem is that we currenly cannot represent the generic signature of
values of type `any P<some P>`. This is because we wind up producing

<Self where Self : P, Self.T == (some P)>

What we'd like to do in the future is erase the errant (some P) with
a fresh generic parameter and keep a substitution map on the side that
records the opaque type constraint. Something like

<Self, Opaque1 where Self : P, Opaque1 : P, Self.T == Opaque1> where Opaque1 == (some P)

Author: CodaFi

validation-test/compiler_crashers_2/unsupported_recursive_opaque_conformance.swift

@@ -0,0 +1,25 @@
+// RUN: not --crash %target-swift-frontend -disable-availability-checking -emit-ir -enable-parameterized-protocol-types %s
+
+// REQUIRES: asserts
+
+protocol P<X: P, Y: P> {
+  var x: X { get }
+  var y: Y { get }
+}
+
+extension Int: P {
+  typealias X = Int
+  typealias Y = Int
+  var x: X { 0 }
+  var y: X { 0 }
+}
+
+struct Foo<T: P>: P {
+  typealias X = T
+  typealias Y = T
+
+  var x: X
+  var y: X { self.x }
+}
+
+func test() -> any P<some P<any P, any P>, some P<any P, any P>> { return Foo<Int>(x: 42) }