Add regression test for https://bugs.swift.org/browse/SR-7002

Author: slavapestov

validation-test/compiler_crashers_2_fixed/sr7002.swift

@@ -0,0 +1,8 @@
+// RUN: not %target-swift-frontend -typecheck %s
+
+struct Foo: OptionSet {
+  let rawValue: Int
+  static let none = Foo(rawValue: 1 << 0)
+}
+
+extension Foo: ExpressibleByIntegerLiteral { }