Add fixed crasher from rdar://problem/54609704

Author: DougGregor

validation-test/compiler_crashers_2_fixed/rdar54609704.swift

@@ -0,0 +1,34 @@
+// RUN: %target-swift-frontend -c %s
+
+@propertyWrapper
+class OneOf<Value: Equatable> {
+  var wrappedValue: Value {
+    get { value }
+    set { storeIfAllowed(newValue) }
+  }
+  
+  private var value: Value
+  
+  private let allowedValues: [Value]
+  
+  init(wrappedValue value: Value, _ allowedValues: Value...) {
+    precondition(allowedValues.contains(value))
+    self.value = value
+    self.allowedValues = allowedValues
+  }
+  
+  private func storeIfAllowed(_ value: Value) {
+    guard allowedValues.contains(value) else {
+      return
+    }
+    
+    self.value = value
+  }
+}
+
+struct Test {
+  @OneOf(4, 8, 15, 16, 23, 42) private var numbers: Int = 4
+}
+func test() {
+  _ = Test()
+}