swift-mirror/test/Constraints/patterns.swift

// RUN: %target-typecheck-verify-swift

// Leaf expression patterns are matched to corresponding pieces of a switch
// subject (TODO: or ~= expression) using ~= overload resolution.
switch (1, 2.5, "three") {
case (1, _, _):
  ()
// Double is ExpressibleByIntegerLiteral
case (_, 2, _),
     (_, 2.5, _),
     (_, _, "three"):
  ()
// ~= overloaded for (Range<Int>, Int)
case (0..<10, _, _),
     (0..<10, 2.5, "three"),
     (0...9, _, _),
     (0...9, 2.5, "three"):
  ()
default:
  ()
}

switch (1, 2) {
case (var a, a): // expected-error {{cannot find 'a' in scope}}
  ()
}

// 'is' patterns can perform the same checks that 'is' expressions do.

protocol P { func p() }

class B : P { 
  init() {} 
  func p() {}
  func b() {}
}
class D : B {
  override init() { super.init() } 
  func d() {}
}
class E {
  init() {} 
  func e() {}
}

struct S : P {
  func p() {}
  func s() {}
}

// Existential-to-concrete.
var bp : P = B()
switch bp {
case is B,
     is D,
     is S:
  ()
case is E:
  ()
default:
  ()
}

switch bp {
case let b as B:
  b.b()
case let d as D:
  d.b()
  d.d()
case let s as S:
  s.s()
case let e as E:
  e.e()
default:
  ()
}

// Super-to-subclass.
var db : B = D()
switch db {
case is D:
  ()
case is E: // expected-warning {{always fails}}
  ()
default:
  ()
}

// Raise an error if pattern productions are used in expressions.
var b = var x // expected-error{{expected initial value after '='}} expected-error {{type annotation missing in pattern}} expected-error {{consecutive statements on a line must be separated by ';'}} {{8-8=;}}
var c = is Int // expected-error{{expected initial value after '='}} expected-error {{expected expression}}  expected-error {{consecutive statements on a line must be separated by ';'}} {{8-8=;}}

// TODO: Bad recovery in these cases. Although patterns are never valid
// expr-unary productions, it would be good to parse them anyway for recovery.
//var e = 2 + var y
//var e = var y + 2

// 'E.Case' can be used in a dynamic type context as an equivalent to
// '.Case as E'.
protocol HairType {}
enum MacbookHair: HairType {
  case HairSupply(S)
}

enum iPadHair<T>: HairType {
  case HairForceOne
}

enum Watch {
  case Sport, Watch, Edition
}

let hair: HairType = MacbookHair.HairSupply(S())
switch hair {
case MacbookHair.HairSupply(let s):
  s.s()
case iPadHair<S>.HairForceOne:
  ()
case iPadHair<E>.HairForceOne:
  ()
case iPadHair.HairForceOne: // expected-error{{generic enum type 'iPadHair' is ambiguous without explicit generic parameters when matching value of type 'any HairType'}}
  ()
case Watch.Edition: // expected-error {{pattern of type 'Watch' cannot match 'any HairType'}}
  ()
case .HairForceOne: // expected-error{{type 'any HairType' has no member 'HairForceOne'}}
  ()
default:
  break
}


// <rdar://problem/19382878> Introduce new x? pattern
switch Optional(42) {
case let x?: break // expected-warning{{immutable value 'x' was never used; consider replacing with '_' or removing it}} {{10-11=_}}
case nil: break
}

// https://github.com/apple/swift/issues/44675
func f_44675(x: Int?) {
    // nil literals should still work when wrapped in parentheses
    switch x {
    case (nil): break
    case _?: break
    }
    switch x {
    case ((nil)): break
    case _?: break
    }
    switch (x, x) {
    case ((nil), _): break
    case (_?, _): break
    }
}

// Test x???? patterns.
switch (nil as Int???) {
case let x???: print(x, terminator: "")
case let x??: print(x as Any, terminator: "")
case let x?: print(x as Any, terminator: "")
case 4???: break
case nil??: break // expected-warning {{case is already handled by previous patterns; consider removing it}}
case nil?: break // expected-warning {{case is already handled by previous patterns; consider removing it}}
default: break
}

switch ("foo" as String?) {
case "what": break
default: break
}


// Test some value patterns.
let x : Int?

extension Int {
  func method() -> Int { return 42 }
}

func ~= <T : Equatable>(lhs: T?, rhs: T?) -> Bool {
  return lhs == rhs
}

switch 4 as Int? {
case x?.method(): break // match value
default: break
}

switch 4 {
case x ?? 42: break // match value
default: break
}

for (var x) in 0...100 {} // expected-warning{{variable 'x' was never used; consider replacing with '_' or removing it}}
for var x in 0...100 {}  // rdar://20167543 expected-warning{{variable 'x' was never used; consider replacing with '_' or removing it}}
for (let x) in 0...100 { _ = x} // expected-error {{'let' pattern cannot appear nested in an already immutable context}}

var (let y) = 42  // expected-error {{'let' cannot appear nested inside another 'var' or 'let' pattern}}
let (var z) = 42  // expected-error {{'var' cannot appear nested inside another 'var' or 'let' pattern}}


// Crash when re-typechecking EnumElementPattern.
// FIXME: This should actually type-check -- the diagnostics are bogus. But
// at least we don't crash anymore.

protocol PP {
  associatedtype E
}

struct A<T> : PP {
  typealias E = T
}

extension PP {
  func map<T>(_ f: (Self.E) -> T) -> T {}
}

enum EE {
  case A
  case B
}

func good(_ a: A<EE>) -> Int {
  return a.map {
    switch $0 {
    case .A:
      return 1
    default:
      return 2
    }
  }
}

func bad(_ a: A<EE>) {
  let _ = a.map {
    let _: EE = $0
    return 1
  }
}

func ugly(_ a: A<EE>) {
  let _ = a.map {
    switch $0 {
    case .A:
      return 1
    default:
      return 2
    }
  }
}

// https://github.com/apple/swift/issues/44666
do {
  enum E {
    case foo
  }

  let x: E?
  if case .foo = x { } // Ok
}

// Invalid 'is' pattern
class SomeClass {}
if case let doesNotExist as SomeClass:AlsoDoesNotExist {}
// expected-error@-1 {{cannot find type 'AlsoDoesNotExist' in scope}}
// expected-error@-2 {{variable binding in a condition requires an initializer}}

// `.foo` and `.bar(...)` pattern syntax should also be able to match
// static members as expr patterns

struct StaticMembers: Equatable {
  init() {}
  init(_: Int) {}
  init?(opt: Int) {}
  static var prop = StaticMembers()
  static var optProp: Optional = StaticMembers()

  static func method(_: Int) -> StaticMembers { return prop }
  static func method(withLabel: Int) -> StaticMembers { return prop }
  static func optMethod(_: Int) -> StaticMembers? { return optProp }

  static func ==(x: StaticMembers, y: StaticMembers) -> Bool { return true }
}

let staticMembers = StaticMembers()
let optStaticMembers: Optional = StaticMembers()

switch staticMembers {
  case .init: break // expected-error{{member 'init(opt:)' expects argument of type 'Int'}}
  case .init(opt:): break // expected-error{{member 'init(opt:)' expects argument of type 'Int'}}
  case .init(): break

  case .init(0): break
  case .init(_): break // expected-error{{'_' can only appear in a pattern}}
  case .init(let x): break // expected-error{{cannot appear in an expression}}
  case .init(opt: 0): break // expected-error{{value of optional type 'StaticMembers?' must be unwrapped to a value of type 'StaticMembers'}}
  // expected-note@-1 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
  // expected-note@-2 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}

  case .prop: break
  case .optProp: break

  case .method: break // expected-error{{member 'method' expects argument of type 'Int'}}
  case .method(0): break
  case .method(_): break // expected-error{{'_' can only appear in a pattern}}
  case .method(let x): break // expected-error{{cannot appear in an expression}}

  case .method(withLabel:): break // expected-error{{member 'method(withLabel:)' expects argument of type 'Int'}}
  case .method(withLabel: 0): break
  case .method(withLabel: _): break // expected-error{{'_' can only appear in a pattern}}
  case .method(withLabel: let x): break // expected-error{{cannot appear in an expression}}

  case .optMethod: break // expected-error{{member 'optMethod' expects argument of type 'Int'}}
  case .optMethod(0): break
}

_ = 0

// rdar://problem/32241441 - Add fix-it for cases in switch with optional chaining

struct S_32241441 {
  enum E_32241441 {
    case foo
    case bar
  }

  var type: E_32241441 = E_32241441.foo
}

func rdar32241441() {
  let s: S_32241441? = S_32241441()

  switch s?.type { // expected-error {{switch must be exhaustive}} expected-note {{add missing case: '.none'}}
  case .foo: // Ok
    break;
  case .bar: // Ok
    break;
  }
}


// https://github.com/apple/swift/issues/48655

struct One<Two> { // expected-note{{'Two' declared as parameter to type 'One'}}
    public enum E: Error {
        // if you remove associated value, everything works
        case SomeError(String)
    }
}

enum HomeworkError: Error {
case dogAteIt
case forgot
}

func testOne() {
  do {
  } catch let error { // expected-warning{{'catch' block is unreachable because no errors are thrown in 'do' block}}
    if case One.E.SomeError = error {} // expected-error{{generic parameter 'Two' could not be inferred}}
  }
  do {
  } catch HomeworkError.forgot { // expected-warning{{'catch' block is unreachable because no errors are thrown in 'do' block}}
  } catch {
  }
}

// https://github.com/apple/swift/issues/50875
// Constrain initializer expressions of optional some pattern bindings to
// be optional.
func test_50875() -> String {
  struct C {
    subscript (s: String) -> String? {
      return ""
    }
    subscript (s: String) -> [String] {
      return [""]
    }

    func f() -> String? {
      return ""
    }
    func f() -> Int {
      return 3
    }

    func g() -> String {
      return ""
    }

    func h() -> String {
      return ""
    }
    func h() -> Double {
      return 3.0
    }
    func h() -> Int? { //expected-note{{found candidate with type '() -> Int?'}}
      return 2
    }
    func h() -> Float? { //expected-note{{found candidate with type '() -> Float?'}}
      return nil
    }

  }

  let c = C()
  if let s = c[""] {
    return s
  }
  if let s = c.f() {
    return s
  }
  if let s = c.g() { //expected-error{{initializer for conditional binding must have Optional type, not 'String'}}
    return s
  }
  if let s = c.h() { //expected-error{{ambiguous use of 'h()'}}
    return s
  }
}

// https://github.com/apple/swift/issues/50338
do {
  enum E {
   case baz
   case bar

      static var member: Self {
          .baz
      }

      static func method() -> Self {
          .bar
      }

      static func methodArg(_: Void) -> Self {
          .baz
      }

      static var none: Self {
          .baz
      }
  }

  let oe: E? = .bar

  switch oe {
   case .bar?: break // Ok
   case .baz: break // Ok
   case .member: break // Ok
   case .missingMember: break // expected-error {{type 'E?' has no member 'missingMember'}}
   case .method(): break // Ok
   case .methodArg(()): break // Ok
   case .none: break // expected-warning {{assuming you mean 'Optional<E>.none'; did you mean 'E.none' instead?}} expected-note {{use 'nil' to silence this warning}} expected-note {{use 'none?' instead}}
   default: break
  }

  let ooe: E?? = .baz

  switch ooe {
   case .bar?: break // Ok
   case .baz: break // Ok
   case .member: break // Ok
   case .missingMember: break // expected-error {{type 'E??' has no member 'missingMember'}}
   case .method(): break // Ok
   case .methodArg(()): break // Ok
   default: break
  }

  if case .baz = ooe {} // Ok
  if case .bar? = ooe {} // Ok
  if case .member = ooe {} // Ok
  if case .missingMember = ooe {} // expected-error {{type 'E??' has no member 'missingMember'}}
  if case .method() = ooe {} // Ok
  if case .methodArg(()) = ooe {} // Ok

  enum M {
    case m
    static func `none`(_: Void) -> Self { .m }
  }

  let om: M? = .m

  switch om {
  case .none: break // Ok
  default: break
  }
}

// rdar://problem/60048356 - `if case` fails when `_` pattern doesn't have a label
func rdar_60048356() {
  typealias Info = (code: ErrorCode, reason: String)

  enum ErrorCode {
    case normalClosure
  }

  enum Failure {
    case closed(Info) // expected-note {{'closed' declared here}}
  }

  enum Reason {
    case close(Failure)
  }

  func test(_ reason: Reason) {
    if case .close(.closed((code: .normalClosure, _))) = reason { // Ok
    }
  }

  // rdar://problem/60061646
  func test(e: Failure) {
    if case .closed(code: .normalClosure, _) = e { // Ok
    // expected-warning@-1 {{enum case 'closed' has one associated value that is a tuple of 2 elements}}
    }
  }

  enum E {
    case foo((x: Int, y: Int)) // expected-note {{declared here}}
    case bar(x: Int, y: Int)   // expected-note {{declared here}}
  }

  func test_destructing(e: E) {
    if case .foo(let x, let y) = e { // Ok (destructring)
    // expected-warning@-1 {{enum case 'foo' has one associated value that is a tuple of 2 elements}}
      _ = x == y
    }
    if case .bar(let tuple) = e { // Ok (matching via tuple)
    // expected-warning@-1 {{enum case 'bar' has 2 associated values; matching them as a tuple is deprecated}}
      _ = tuple.0 == tuple.1
    }
  }
}

// rdar://problem/63510989 - valid pattern doesn't type-check
func rdar63510989() {
  enum Value : P {
    func p() {}
  }

  enum E {
    case single(P?)
    case double(P??)
    case triple(P???)
  }

  func test(e: E) {
    if case .single(_) = e {} // Ok
    if case .single(_ as Value) = e {} // Ok
    if case .single(let v as Value) = e {} // Ok
    // expected-warning@-1 {{immutable value 'v' was never used; consider replacing with '_' or removing it}}
    if case .double(_ as Value) = e {} // Ok
    if case .double(let v as Value) = e {} // Ok
    // expected-warning@-1 {{immutable value 'v' was never used; consider replacing with '_' or removing it}}
    if case .double(let v as Value?) = e {} // Ok
    // expected-warning@-1 {{immutable value 'v' was never used; consider replacing with '_' or removing it}}
    if case .triple(_ as Value) = e {} // Ok
    if case .triple(let v as Value) = e {} // Ok
    // expected-warning@-1 {{immutable value 'v' was never used; consider replacing with '_' or removing it}}
    if case .triple(let v as Value?) = e {} // Ok
    // expected-warning@-1 {{immutable value 'v' was never used; consider replacing with '_' or removing it}}
    if case .triple(let v as Value??) = e {} // Ok
    // expected-warning@-1 {{immutable value 'v' was never used; consider replacing with '_' or removing it}}
  }
}

// rdar://problem/64157451 - compiler crash when using undefined type in pattern
func rdar64157451() {
  enum E {
  case foo(Int)
  }

  func test(e: E) {
    if case .foo(let v as DoeNotExist) = e {} // expected-error {{cannot find type 'DoeNotExist' in scope}}
  }
}

// rdar://80797176 - circular reference incorrectly diagnosed while reaching for a type of a pattern.
func rdar80797176 () {
  for x: Int in [1, 2] where x.bitWidth == 32 { // Ok
  }
}

// https://github.com/apple/swift/issues/60029
for (key, values) in oldName { // expected-error{{cannot find 'oldName' in scope}}
  for (idx, value) in values.enumerated() {
    print(key, idx, value)
  }
}

// https://github.com/apple/swift/issues/60503
func f60503() {
  let (key, _) = settings.enumerate() // expected-error{{cannot find 'settings' in scope}}
  let (_, _) = settings.enumerate() // expected-error{{cannot find 'settings' in scope}}
}

// rdar://105089074
enum EWithIdent<Id> where Id: P {
case test(Id)
}

extension [EWithIdent<Int>] { // expected-error {{type 'Int' does not conform to protocol 'P'}}
  func test() {
    sorted { lhs, rhs in
      switch (rhs, rhs) {
      case let (.test(x), .test(y)): break
        // expected-error@-1 2 {{type 'Element' has no member 'test'}}
      case (_, _): break
      }
    }
  }
}

struct TestIUOMatchOp {
  static func ~= (lhs: TestIUOMatchOp, rhs: TestIUOMatchOp) -> Bool! { nil }
  func foo() {
    if case self = self {}
  }
}

struct TestRecursiveVarRef<T> {
  lazy var e: () -> Int = {e}()
}

func testMultiStmtClosureExprPattern(_ x: Int) {
  if case { (); return x }() = x {}
}

func testExprPatternIsolation() {
  // We type-check ExprPatterns separately, so these are illegal.
  if case 0 = nil {} // expected-error {{'nil' requires a contextual type}}
  let _ = {
    if case 0 = nil {} // expected-error {{'nil' requires a contextual type}}
  }
  for case 0 in nil {} // expected-error {{'nil' requires a contextual type}}
  for case 0 in [nil] {}
  // expected-error@-1 {{type 'Any' cannot conform to 'Equatable'}}
  // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
  // expected-note@-3 {{requirement from conditional conformance of 'Any?' to 'Equatable'}}

  // Though we will try Double for an integer literal...
  let d: Double = 0
  if case d = 0 {}
  let _ = {
    if case d = 0 {}
  }
  for case d in [0] {}

  // But not Float
  let f: Float = 0
  if case f = 0 {} // expected-error {{expression pattern of type 'Float' cannot match values of type 'Int'}}
  let _ = {
    if case f = 0 {} // expected-error {{expression pattern of type 'Float' cannot match values of type 'Int'}}
  }
  for case f in [0] {}  // expected-error {{expression pattern of type 'Float' cannot match values of type 'Int'}}

  enum MultiPayload<T: Equatable>: Equatable {
    case e(T, T)
    static func f(_ x: T, _ y: T) -> Self { .e(x, y) }
  }
  enum E: Equatable {
    case a, b
    static var c: E { .a }
    static var d: E { .b }
  }

  func produceMultiPayload<T>() -> MultiPayload<T> { fatalError() }

  // We type-check ExprPatterns left to right, so only one of these works.
  if case .e(0.0, 0) = produceMultiPayload() {}
  if case .e(0, 0.0) = produceMultiPayload() {} // expected-error {{expression pattern of type 'Double' cannot match values of type 'Int'}}

  for case .e(0.0, 0) in [produceMultiPayload()] {}
  for case .e(0, 0.0) in [produceMultiPayload()] {} // expected-error {{expression pattern of type 'Double' cannot match values of type 'Int'}}

  // Same, because although it's a top-level ExprPattern, we don't resolve
  // that until during solving.
  if case .f(0.0, 0) = produceMultiPayload() {}
  if case .f(0, 0.0) = produceMultiPayload() {} // expected-error {{expression pattern of type 'Double' cannot match values of type 'Int'}}

  if case .e(5, nil) = produceMultiPayload() {} // expected-warning {{type 'Int' is not optional, value can never be nil; this is an error in the Swift 6 language mode}}

  // FIXME: Bad error (https://github.com/apple/swift/issues/64279)
  if case .e(nil, 0) = produceMultiPayload() {}
  // expected-error@-1 {{expression pattern of type 'String' cannot match values of type 'Substring'}}
  // expected-note@-2 {{overloads for '~=' exist with these partially matching parameter lists}}

  if case .e(5, nil) = produceMultiPayload() as MultiPayload<Int?> {}
  if case .e(nil, 0) = produceMultiPayload() as MultiPayload<Int?> {}

  // Enum patterns are solved together.
  if case .e(E.a, .b) = produceMultiPayload() {}
  if case .e(.a, E.b) = produceMultiPayload() {}

  // These also work because they start life as EnumPatterns.
  if case .e(E.c, .d) = produceMultiPayload() {}
  if case .e(.c, E.d) = produceMultiPayload() {}
  for case .e(E.c, .d) in [produceMultiPayload()] {}
  for case .e(.c, E.d) in [produceMultiPayload()] {}

  // Silly, but allowed.
  if case 0: Int? = 0 {} // expected-warning {{non-optional expression of type 'Int' used in a check for optionals}}

  var opt: Int?
  if case opt = 0 {}
}

enum LotsOfOptional {
  case yup(Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?, Int?)
}
func testLotsOfNil(_ x: LotsOfOptional) {
  if case .yup(nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil, nil) = x {}
}

// https://github.com/apple/swift/issues/66752
// FIXME: We ought to improve the diagnostics here
func issue66752(_ x: Result<String, Error>) {
  let _ = {
    if case .failure() = x {}
    // expected-error@-1 {{type '()' cannot conform to 'Error}}
    // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
    // expected-note@-3 {{required by generic enum 'Result' where 'Failure' = '()'}}
  }
  let _ = {
    if case (.failure(), let y) = (x, 0) {}
    // expected-error@-1 {{type '()' cannot conform to 'Error}}
    // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
    // expected-note@-3 {{required by generic enum 'Result' where 'Failure' = '()'}}
  }
  if case .failure() = x {}
  // expected-error@-1 {{type '()' cannot conform to 'Error}}
  // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
  // expected-note@-3 {{required by generic enum 'Result' where 'Failure' = '()'}}
  
  if case (.failure(), let y) = (x, 0) {}
  // expected-error@-1 {{type '()' cannot conform to 'Error}}
  // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
  // expected-note@-3 {{required by generic enum 'Result' where 'Failure' = '()'}}
}

// https://github.com/apple/swift/issues/66750
// FIXME: We ought to improve the diagnostics here
func issue66750(_ x: Result<String, Error>) {
  let _ = {
    switch x {
    case .success:
      "a"
    case .failure():
      // expected-error@-1 {{type '()' cannot conform to 'Error}}
      // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
      // expected-note@-3 {{required by generic enum 'Result' where 'Failure' = '()'}}
      "b"
    }
  }
  let _ = {
    switch (x, 0) {
    case (.success, let y):
      "a"
    case (.failure(), let y):
      // expected-error@-1 {{type '()' cannot conform to 'Error}}
      // expected-note@-2 {{only concrete types such as structs, enums and classes can conform to protocols}}
      // expected-note@-3 {{required by generic enum 'Result' where 'Failure' = '()'}}
      "b"
    }
  }
  switch x {
  case .success:
    break
  case .failure(): // expected-error {{tuple pattern cannot match values of the non-tuple type 'any Error'}}
    break
  }
  switch (x, 0) {
  case (.success, let y):
    break
  case (.failure(), let y):
    // expected-error@-1 {{tuple pattern cannot match values of the non-tuple type 'any Error'}}
    break
  }
}

// rdar://123466496 - `type of expression is ambiguous without a type annotation` with extra elements
do {
  enum E {
  case test(a: Int, b: String)
  }

  func test(_: (E) -> Void) {
  }

  test {
    switch $0 {
    case .test(a: 42, b: "", c: 0.0): break
      // expected-error@-1 {{tuple pattern has the wrong length for tuple type '(Int, String)'}}
    }
  }
}

func testMatchingNonErrorConformingTypeInClosure(_ x: any Error) {
  enum E {
    case e
  }
  _ = {
    switch x {
    case E.e: // expected-error {{pattern of type 'E' does not conform to expected match type 'Error'}}
      break
    default:
      break
    }
  }
}

// rdar://131819800 - crash in `transformWithPosition` while trying to emit diagnostics for `AllowFunctionTypeMismatch` fix
do {
  enum E {
  case test(kind: Int, defaultsToEmpty: Bool = false)
  }

  func test(e: E) {
    if case .test(kind: _, // expected-error {{tuple pattern has the wrong length for tuple type '(Int, Bool)'}}
                  name: let name?,
                  defaultsToEmpty: _,
                  deprecateName: let deprecatedName?) = e {
    }
  }
}

// Make sure we diagnose 'Undefined' here.
func testUndefinedTypeInPattern(_ x: Int) {
  switch x {
  case Optional<Undefined>.alsoUndefined: // expected-error {{cannot find type 'Undefined' in scope}}
    break
  }
  _ = {
    switch x {
    case Optional<Undefined>.alsoUndefined: // expected-error {{cannot find type 'Undefined' in scope}}
      break
    }
  }
}

func testUndefinedInClosureVar() {
  // Make sure we don't produce "unable to infer closure type without a type annotation"
  _ = {
    var x: Undefined // expected-error {{cannot find type 'Undefined' in scope}}
  }
}