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

func myMap<T1, T2>(_ array: [T1], _ fn: (T1) -> T2) -> [T2] {}

var intArray : [Int]

_ = myMap(intArray, { String($0) })
_ = myMap(intArray, { x -> String in String(x) } )

// Closures with too few parameters.
func foo(_ x: (Int, Int) -> Int) {}
foo({$0}) // expected-error{{contextual closure type '(Int, Int) -> Int' expects 2 arguments, but 1 was used in closure body}}
foo({ [intArray] in $0}) // expected-error{{contextual closure type '(Int, Int) -> Int' expects 2 arguments, but 1 was used in closure body}}

struct X {}
func mySort(_ array: [String], _ predicate: (String, String) -> Bool) -> [String] {}
func mySort(_ array: [X], _ predicate: (X, X) -> Bool) -> [X] {}
var strings : [String]
_ = mySort(strings, { x, y in x < y })

// Closures with inout arguments.
func f0<T, U>(_ t: T, _ f: (inout T) -> U) -> U {
  var t2 = t
  return f(&t2)
}

struct X2 {
  func g() -> Float { return 0 }  
}

_ = f0(X2(), {$0.g()})

// Closures with inout arguments and '__shared' conversions.

func inoutToSharedConversions() {
  func fooOW<T, U>(_ f : (__owned T) -> U) {}
  fooOW({ (x : Int) in return Int(5) }) // defaut-to-'__owned' allowed
  fooOW({ (x : __owned Int) in return Int(5) }) // '__owned'-to-'__owned' allowed
  fooOW({ (x : __shared Int) in return Int(5) }) // '__shared'-to-'__owned' allowed
  fooOW({ (x : inout Int) in return Int(5) }) // expected-error {{cannot convert value of type '(inout Int) -> Int' to expected argument type '(__owned Int) -> Int'}}
  
  func fooIO<T, U>(_ f : (inout T) -> U) {}
  fooIO({ (x : inout Int) in return Int(5) }) // 'inout'-to-'inout' allowed
  fooIO({ (x : Int) in return Int(5) }) // expected-error {{cannot convert value of type '(Int) -> Int' to expected argument type '(inout Int) -> Int'}}
  fooIO({ (x : __shared Int) in return Int(5) }) // expected-error {{cannot convert value of type '(__shared Int) -> Int' to expected argument type '(inout Int) -> Int'}}
  fooIO({ (x : __owned Int) in return Int(5) }) // expected-error {{cannot convert value of type '(__owned Int) -> Int' to expected argument type '(inout Int) -> Int'}}

  func fooSH<T, U>(_ f : (__shared T) -> U) {}
  fooSH({ (x : __shared Int) in return Int(5) }) // '__shared'-to-'__shared' allowed
  fooSH({ (x : __owned Int) in return Int(5) }) // '__owned'-to-'__shared' allowed
  fooSH({ (x : inout Int) in return Int(5) }) // expected-error {{cannot convert value of type '(inout Int) -> Int' to expected argument type '(__shared Int) -> Int'}}
  fooSH({ (x : Int) in return Int(5) }) // default-to-'__shared' allowed
}

// Autoclosure
func f1(f: @autoclosure () -> Int) { }
func f2() -> Int { }
f1(f: f2) // expected-error{{add () to forward '@autoclosure' parameter}}{{9-9=()}}
f1(f: 5)

// Ternary in closure
var evenOrOdd : (Int) -> String = {$0 % 2 == 0 ? "even" : "odd"}

// <rdar://problem/15367882>
func foo() {
  not_declared({ $0 + 1 }) // expected-error{{cannot find 'not_declared' in scope}}
}

// <rdar://problem/15536725>
struct X3<T> {
  init(_: (T) -> ()) {}
}

func testX3(_ x: Int) {
  var x = x
  _ = X3({ x = $0 })
  _ = x
}

// <rdar://problem/13811882>
func test13811882() {
  var _ : (Int) -> (Int, Int) = {($0, $0)}
  var x = 1
  var _ : (Int) -> (Int, Int) = {($0, x)}
  x = 2
}


/// <rdar://problem/21544303>
/// https://github.com/apple/swift/issues/46256
/// QoI: "Unexpected trailing closure" should have a fixit to insert a `do`
/// statement
do {
  var inSubcall = true 
  {  // expected-error {{closure expression is unused}} expected-note {{did you mean to use a 'do' statement?}}
  }  
  inSubcall = false

  // These are a problems, but it's not clear what was intended.
  var somethingElse = true {
  // expected-error@-1 {{computed property must have an explicit type}}
  // expected-error@-2 {{variable with getter/setter cannot have an initial value}}
  }
  var somethingElseWithTypeAnno: Bool = true {} // expected-error {{variable with getter/setter cannot have an initial value}}
  inSubcall = false

  var v2 : Bool = false
  v2 = inSubcall // expected-error {{cannot call value of non-function type 'Bool'}}
  {
  }
}


// https://github.com/apple/swift/issues/46256
do {
  let n = 42
  func consume(_ x: Int) {}

  { consume($0) }(42)
  ;

  ({ $0(42) } { consume($0) }) // expected-error {{cannot call value of non-function type '()'}} expected-note {{callee is here}}

  { print(42) }  // expected-warning {{braces here form a trailing closure separated from its callee by multiple newlines}} expected-note {{did you mean to use a 'do' statement?}} {{3-3=do }}
  ;

  ({ $0(42) } { consume($0) }) // expected-error {{cannot call value of non-function type '()'}} expected-note {{callee is here}}

  { print($0) }  // expected-warning {{braces here form a trailing closure separated from its callee by multiple newlines}}
  ;

  ({ $0(42) } { consume($0) }) // expected-error {{cannot call value of non-function type '()'}} expected-note {{callee is here}}

  { [n] in print(42) }  // expected-warning {{braces here form a trailing closure separated from its callee by multiple newlines}}
  ;

  ({ $0(42) } { consume($0) }) // expected-error {{cannot call value of non-function type '()'}} expected-note {{callee is here}}

  { consume($0) }(42)  // expected-warning {{braces here form a trailing closure separated from its callee by multiple newlines}}
  ;

  ({ $0(42) } { consume($0) }) // expected-error {{cannot call value of non-function type '()'}} expected-note {{callee is here}}

  { (x: Int) in consume(x) }(42)  // expected-warning {{braces here form a trailing closure separated from its callee by multiple newlines}}
  ;

  // This is technically a valid call, so nothing goes wrong until (42)

  { $0(3) } // expected-error {{cannot call value of non-function type '()'}}
  { consume($0) }(42)
  ;
  ({ $0(42) }) // expected-error {{cannot call value of non-function type '()'}}
  { consume($0) }(42)
  ;
  { $0(3) } // expected-error {{cannot call value of non-function type '()'}}
  { [n] in consume($0) }(42)
  ;
  ({ $0(42) }) // expected-error {{cannot call value of non-function type '()'}}
  { [n] in consume($0) }(42)
  ;

  // Equivalent but more obviously unintended.

  { $0(3) }  // expected-error {{cannot call value of non-function type '()'}} expected-note {{callee is here}}

  { consume($0) }(42)
  // expected-warning@-1 {{braces here form a trailing closure separated from its callee by multiple newlines}}

  ({ $0(3) })  // expected-error {{cannot call value of non-function type '()'}} expected-note {{callee is here}}

  { consume($0) }(42)
  // expected-warning@-1 {{braces here form a trailing closure separated from its callee by multiple newlines}}
  ;

  // Also a valid call (!!)
  { $0 { $0 } } { $0 { 1 } }  // expected-error {{function is unused}}
  consume(111)
}


// <rdar://problem/22162441> Crash from failing to diagnose nonexistent method access inside closure
func r22162441(_ lines: [String]) {
  _ = lines.map { line in line.fooBar() }  // expected-error {{value of type 'String' has no member 'fooBar'}}
  _ = lines.map { $0.fooBar() }  // expected-error {{value of type 'String' has no member 'fooBar'}}
}


func testMap() {
  let a = 42
  [1,a].map { $0 + 1.0 } // expected-error {{cannot convert value of type 'Int' to expected element type 'Double'}}
}

// <rdar://problem/22414757> "UnresolvedDot" "in wrong phase" assertion from verifier
[].reduce { $0 + $1 }  // expected-error {{missing argument for parameter #1 in call}}




// <rdar://problem/22333281> QoI: improve diagnostic when contextual type of closure disagrees with arguments
var _: () -> Int = {0}

// expected-error @+1 {{contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored}} {{24-24=_ in }}
var _: (Int) -> Int = {0}

// expected-error @+1 {{contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored}} {{24-24= _ in}}
var _: (Int) -> Int = { 0 }

// expected-error @+1 {{contextual type for closure argument list expects 2 arguments, which cannot be implicitly ignored}} {{29-29=_,_ in }}
var _: (Int, Int) -> Int = {0}

// expected-error @+1 {{contextual closure type '(Int, Int) -> Int' expects 2 arguments, but 3 were used in closure body}}
var _: (Int,Int) -> Int = {$0+$1+$2}

// expected-error @+1 {{contextual closure type '(Int, Int, Int) -> Int' expects 3 arguments, but 2 were used in closure body}}
var _: (Int, Int, Int) -> Int = {$0+$1}


// expected-error @+1 {{contextual closure type '(Int) -> Int' expects 1 argument, but 2 were used in closure body}}
var _: (Int) -> Int = {a,b in 0}

// expected-error @+1 {{contextual closure type '(Int) -> Int' expects 1 argument, but 3 were used in closure body}}
var _: (Int) -> Int = {a,b,c in 0}

// expected-error @+1 {{contextual closure type '(Int, Int, Int) -> Int' expects 3 arguments, but 2 were used in closure body}}
var _: (Int, Int, Int) -> Int = {a, b in a+b}

// <rdar://problem/15998821> Fail to infer types for closure that takes an inout argument
func r15998821() {
  func take_closure(_ x : (inout Int) -> ()) { }

  func test1() {
    take_closure { (a : inout Int) in
      a = 42
    }
  }

  func test2() {
    take_closure { a in
      a = 42
    }
  }

  func withPtr(_ body: (inout Int) -> Int) {}
  func f() { withPtr { p in return p } }

  let g = { x in x = 3 }
  take_closure(g)
}

// <rdar://problem/22602657> better diagnostics for closures w/o "in" clause
var _: (Int,Int) -> Int = {$0+$1+$2}  // expected-error {{contextual closure type '(Int, Int) -> Int' expects 2 arguments, but 3 were used in closure body}}


// Crash when re-typechecking bodies of non-single expression closures

struct CC {}
func callCC<U>(_ f: (CC) -> U) -> () {}

func typeCheckMultiStmtClosureCrash() {
  callCC {
    _ = $0
    return 1
  }
}

// https://github.com/apple/swift/issues/43444

func someFunc(_ foo: ((String) -> String)?,
              bar: @escaping (String) -> String) {
    let _: (String) -> String = foo != nil ? foo! : bar
    let _: (String) -> String = foo ?? bar
}

func verify_NotAC_to_AC_failure(_ arg: () -> ()) {
  func takesAC(_ arg: @autoclosure () -> ()) {}
  takesAC(arg) // expected-error {{add () to forward '@autoclosure' parameter}} {{14-14=()}}
}

// https://github.com/apple/swift/issues/43681
// Error diagnostic refers to wrong argument
do {
  class C1<T> {
    func append<Key: AnyObject>(value: T, forKey key: Key) where Key: Hashable {}
  }
  class C2<T> {
    let c1: C1<(AnyObject, T) -> ()> = C1()
  }
  struct S<T> {
    let cs: [C2<T>] = []

    func subscribe<Object: AnyObject>(object: Object?, method: (Object, T) -> ()) where Object: Hashable {
      let wrappedMethod = { (object: AnyObject, value: T) in }
      cs.forEach { $0.c1.append(value: wrappedMethod, forKey: object) }
      // expected-error@-1 {{value of optional type 'Object?' must be unwrapped to a value of type 'Object'}}
      // expected-note@-2 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}
      // expected-note@-3 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
    }
  }
}

// Similar to https://github.com/apple/swift/issues/43681 but with multiple
// generic arguments.
do {
  class C {}
  struct S {
    func genericallyNonOptional<T: AnyObject>(_ a: T, _ b: T, _ c: T) { }
    // expected-note@-1 {{where 'T' = 'Optional<C>'}}

    func f(_ a: C?, _ b: C?, _ c: C) {
      genericallyNonOptional(a, b, c) // expected-error {{instance method 'genericallyNonOptional' requires that 'Optional<C>' be a class type}}
      // expected-note @-1 {{wrapped type 'C' satisfies this requirement}}
    }
  }
}

// Make sure we cannot infer an () argument from an empty parameter list.
func acceptNothingToInt (_: () -> Int) {}
func testAcceptNothingToInt(ac1: @autoclosure () -> Int) {
  acceptNothingToInt({ac1($0)}) // expected-error@:27 {{argument passed to call that takes no arguments}}
  // expected-error@-1{{contextual closure type '() -> Int' expects 0 arguments, but 1 was used in closure body}}
}

// <rdar://problem/23570873> QoI: Poor error calling map without being able to infer "U" (closure result inference)
struct Thing {
  init?() {}
}

let things = Thing().map { thing in
  _ = thing
  return thing
}


// <rdar://problem/21675896> QoI: [Closure return type inference] Swift cannot find members for the result of inlined lambdas with branches
func r21675896(file : String) {
  let x: String = {
    if true {
      return "foo"
    }
    else {
      return file
    }
  }().pathExtension // expected-error {{value of type 'String' has no member 'pathExtension'}}
}




// <rdar://problem/19870975> Incorrect diagnostic for failed member lookups within closures passed as arguments ("(_) -> _")
func ident<T>(_ t: T) -> T {}
var c = ident({1.DOESNT_EXIST}) // error: expected-error {{value of type 'Int' has no member 'DOESNT_EXIST'}}

// <rdar://problem/20712541> QoI: Int/UInt mismatch produces useless error inside a block
var afterMessageCount : Int?

func uintFunc() -> UInt {}
func takeVoidVoidFn(_ a : () -> ()) {}
takeVoidVoidFn { () -> Void in
  afterMessageCount = uintFunc()  // expected-error {{cannot assign value of type 'UInt' to type 'Int'}} {{23-23=Int(}} {{33-33=)}}
}

// <rdar://problem/19997471> Swift: Incorrect compile error when calling a function inside a closure
func f19997471(_ x: String) {} // expected-note {{candidate expects value of type 'String' for parameter #1 (got 'T')}}
func f19997471(_ x: Int) {}    // expected-note {{candidate expects value of type 'Int' for parameter #1 (got 'T')}}

func someGeneric19997471<T>(_ x: T) {
  takeVoidVoidFn {
    f19997471(x) // expected-error {{no exact matches in call to global function 'f19997471'}}
  }
}


// <rdar://problem/20921068> Swift fails to compile: [0].map() { _ in let r = (1,2).0; return r }
let _ = [0].map {
  _ in
  let r =  (1,2).0
  return r
}


// <rdar://problem/21078316> Less than useful error message when using map on optional dictionary type
func rdar21078316() {
  var foo : [String : String]?
  var bar : [(String, String)]?
  bar = foo.map { ($0, $1) }  // expected-error {{contextual closure type '([String : String]) -> [(String, String)]' expects 1 argument, but 2 were used in closure body}}
  // expected-error@-1{{cannot convert value of type '(Dictionary<String, String>, _)' to closure result type '[(String, String)]'}}
}


// <rdar://problem/20978044> QoI: Poor diagnostic when using an incorrect tuple element in a closure
var numbers = [1, 2, 3]
zip(numbers, numbers).filter { $0.2 > 1 }  // expected-error {{value of tuple type 'Zip2Sequence<[Int], [Int]>.Element' (aka '(Int, Int)') has no member '2'}}



// <rdar://problem/20868864> QoI: Cannot invoke 'function' with an argument list of type 'type'
func foo20868864(_ callback: ([String]) -> ()) { }
func rdar20868864(_ s: String) {
  var s = s
  foo20868864 { (strings: [String]) in
    s = strings   // expected-error {{cannot assign value of type '[String]' to type 'String'}}
  }
}

// <rdar://problem/22058555> crash in cs diags in withCString
func r22058555() {
  var firstChar: UInt8 = 0
  "abc".withCString { chars in
    firstChar = chars[0]  // expected-error {{cannot assign value of type 'Int8' to type 'UInt8'}} {{17-17=UInt8(}} {{25-25=)}}
  }
}

// <rdar://problem/20789423> Unclear diagnostic for multi-statement closure with no return type
func r20789423() {
  class C {
    func f(_ value: Int) { }
  }
  
  let p: C
  print(p.f(p)())  // expected-error {{cannot convert value of type 'C' to expected argument type 'Int'}}
  // expected-error@-1:11 {{cannot call value of non-function type '()'}}
  
  let _f = { (v: Int) in
    print("a")
    return "hi"
  }
  
}

/// In the example below, https://github.com/apple/swift/issues/45110 started
/// preferring `C_45110.test(_:)` over `P_45110.test(it:)`. Prior to Swift 5.1,
/// we emulated the old behavior. However, that behavior is inconsistent with
/// the typical approach of preferring overloads from the concrete type over one
/// from a protocol, so we removed the hack.
protocol Initable_45110 { init() }

protocol P_45110 {
  associatedtype T: Initable_45110
}
extension P_45110 {
  func test(it o: (T) -> Bool) -> Bool {
    return o(T.self())
  }
}

struct S_45110 : Initable_45110 {}
class C_45110 : P_45110 {
  typealias T = S_45110

  func test(_ o: Any) -> Bool {
    return false
  }

  func call(_ c: C_45110) -> Bool {
    // Note: the diagnostic about capturing 'self', indicates that we have
    // selected test(_) rather than test(it:)
    return c.test { o in test(o) } // expected-error{{call to method 'test' in closure requires explicit use of 'self' to make capture semantics explicit}} expected-note{{capture 'self' explicitly to enable implicit 'self' in this closure}} expected-note{{reference 'self.' explicitly}}
  }
}

let _ = C_45110().call(C_45110())

// <rdar://problem/28909024> Returning incorrect result type from method invocation can result in nonsense diagnostic
extension Collection {
  func r28909024(_ predicate: (Iterator.Element)->Bool) -> Index {
    return startIndex
  }
}
func fn_r28909024(n: Int) {
  return (0..<10).r28909024 { // expected-error {{unexpected non-void return value in void function}} // expected-note {{did you mean to add a return type?}}
    _ in true
  }
}

// https://github.com/apple/swift/issues/45584
// Unexpected ambiguous expression in closure with generics
do {
  struct S {
    var dataOffset: Int
  }
  class C<R> {
    init(arg: (R) -> Void) {}
  }
  func f(arg: String) {}
  func g(arg: Int) -> Double {
    return 2
  }

  C<S>(arg: { (r: S) in f(arg: g(arg: r.dataOffset)) }) // expected-error {{cannot convert value of type 'Double' to expected argument type 'String'}}

  let _ = { $0[$1] }(1, 1) // expected-error {{value of type 'Int' has no subscripts}}
  // FIXME: Better diagnostic here would be `assigning a variable to itself` but
  // binding ordering change exposed a bug in diagnostics.
  let _ = { $0 = ($0 = {}) } // expected-error {{function produces expected type '()'; did you mean to call it with '()'?}}
  let _ = { $0 = $0 = 42 } // expected-error {{assigning a variable to itself}}
}

// https://github.com/apple/swift/issues/43020
// The () -> T => () -> () implicit conversion was kicking in anywhere
// inside a closure result, not just at the top-level.
let mismatchInClosureResultType : (String) -> ((Int) -> Void) = {
  (String) -> ((Int) -> Void) in
    return { }
    // expected-error@-1 {{contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored}} {{13-13= _ in}}
}

// https://github.com/apple/swift/issues/46108
// Generic function taking closure with in-out parameter can result in a variety
// of compiler errors or EXC_BAD_ACCESS
do {
  func f<T>(_ g: (inout T) -> Int) {}
  f { $0 = 1 } // expected-error {{cannot convert value of type '()' to closure result type 'Int'}}

  // This test makes sure that having closure with in-out parameter doesn't
  // crash with member lookup.
  struct S {
    var number1: Int
  }
  func set_via_closure<T, U>(_ closure: (inout T, U) -> ()) {} // expected-note {{in call to function 'set_via_closure'}}
  set_via_closure({ $0.number1 = $1 })
  // expected-error@-1 {{generic parameter 'T' could not be inferred}}
  // expected-error@-2 {{cannot infer type of closure parameter '$1' without a type annotation}}

  func f2<T>(_ item: T, _ update: (inout T) -> Void) {
    var x = item
    update(&x)
  }
  var arg = 42
  f2(arg) { $0 += 3 } // ok
}

/// https://github.com/apple/swift/issues/44585
/// https://github.com/apple/swift/issues/45663
/// Inference of `inout`
do {
  func f<T>(_ closure: (inout T) -> Void) {}
  f({ $0 += 2 }) // ok
}

/// https://github.com/apple/swift/issues/45663
/// `UnresolvedDotExpr` in single expression closure
do {
  struct Lense<Whole, Part> {
    let set: (inout Whole, Part) -> ()
  }
  struct S {
    var number1: Int
    func lenses() {
      let _: Lense<S, Int> = Lense(
        set: { $0.number1 = $1 } // ok
      )
    }
  }
}

// https://github.com/apple/swift/issues/46067
// Segmentation fault and other error for closure with in-out parameter
do {
  func unfold<A, B>(_ a0: A, next: (inout A) -> B) {}
  unfold((0, 0)) { s in 0 } // ok
}

// https://github.com/apple/swift/issues/46343
// Swift 3.1 fails to compile 3.0 code involving closures and IUOs
let _: ((Any?) -> Void) = { (arg: Any!) in }
// This example was rejected in 3.0 as well, but accepting it is correct.
let _: ((Int?) -> Void) = { (arg: Int!) in }

// rdar://30429709 - We should not attempt an implicit conversion from
// () -> T to () -> Optional<()>.
func returnsArray() -> [Int] { return [] }

returnsArray().compactMap { $0 }.compactMap { }
// expected-warning@-1 {{expression of type 'Int' is unused}}
// expected-warning@-2 {{result of call to 'compactMap' is unused}}

// rdar://problem/30271695
_ = ["hi"].compactMap { $0.isEmpty ? nil : $0 }

// rdar://problem/32432145 - compiler should emit fixit to remove "_ in" in closures if 0 parameters is expected

func r32432145(_ a: () -> ()) {}

r32432145 { _ in let _ = 42 }
// expected-error@-1 {{contextual closure type '() -> ()' expects 0 arguments, but 1 was used in closure body}} {{13-17=}}

r32432145 { _ in
  // expected-error@-1 {{contextual closure type '() -> ()' expects 0 arguments, but 1 was used in closure body}} {{13-17=}}
  print("answer is 42")
}

r32432145 { _,_ in
  // expected-error@-1 {{contextual closure type '() -> ()' expects 0 arguments, but 2 were used in closure body}} {{13-19=}}
  print("answer is 42")
}

// rdar://problem/30106822 - Swift ignores type error in closure and presents a bogus error about the caller
[1, 2].first { $0.foo = 3 }
// expected-error@-1 {{value of type 'Int' has no member 'foo'}}

// rdar://problem/32433193
// https://github.com/apple/swift/issues/47606
// Higher-order function diagnostic mentions the wrong contextual type
// conversion problem

protocol P_47606 {
  associatedtype Value
  func map<U>(_ t : @escaping (Self.Value) -> U) -> S_47606<U>
}

struct S_47606<T> : P_47606 {
  typealias Value = T
  func map<U>(_ t : @escaping (T) -> U) -> S_47606<U> { fatalError() }
}

func exFalso_47606<T>() -> T {}

extension P_47606 {
  func foo() -> S_47606<Int> {
    let tt : S_47606<Int> = exFalso_47606()
    return tt.map { x in (idx: x) }
    // expected-error@-1 {{cannot convert value of type '(idx: Int)' to closure result type 'Int'}}
  }
}

// rdar://problem/33296619
let u = rdar33296619().element //expected-error {{cannot find 'rdar33296619' in scope}}

[1].forEach { _ in
  _ = "\(u)" // No diagnostic because `u` is already diagnosed and marked as invalid
}

[1].forEach { _ in
  _ = 1 + "hi" // expected-error {{binary operator '+' cannot be applied to operands of type 'Int' and 'String'}}
  // expected-note@-1 {{overloads for '+' exist with these partially matching parameter lists: (Int, Int), (String, String)}}
}

// https://github.com/apple/swift/issues/48236
do {
  class C {
    var property: String?
  }

  func test(cs: [C?]) -> [String?] {
    return cs.map({ c in
        let a = c.propertyWithTypo ?? "default"
        // expected-error@-1 {{value of type 'C?' has no member 'propertyWithTypo'}}
        let b = "\(a)"
        return b
      })
  }
}

// Ensure that we still do the appropriate pointer conversion here.
_ = "".withCString { UnsafeMutableRawPointer(mutating: $0) }

// rdar://problem/34077439 - Crash when pre-checking bails out and
// leaves us with unfolded SequenceExprs inside closure body.
_ = { (offset) -> T in // expected-error {{cannot find type 'T' in scope}}
  return offset ? 0 : 0
}

// https://github.com/apple/swift/issues/47778
do {
  struct S<T> {
    func map<R>(fn: (T) -> R) {}
  }

  S<()>().map{ return 0 }
  S<()>().map{ _ in return 0 }
  S<Void>().map{ return 0 }
  S<Void>().map{ _ in return 0 }
}

// rdar://problem/33429010

struct I_33429010 : IteratorProtocol {
    func next() -> Int? {
        fatalError()
    }
}

extension Sequence {
    public func rdar33429010<Result>(into initialResult: Result,
                                     _ nextPartialResult: (_ partialResult: inout Result, Iterator.Element) throws -> ()
        ) rethrows -> Result {
        return initialResult
    }
}

extension Int {
   public mutating func rdar33429010_incr(_ inc: Int) {
     self += inc
   }
}

func rdar33429010_2() {
  let iter = I_33429010()
  var acc: Int = 0 // expected-warning {{}}
  let _: Int = AnySequence { iter }.rdar33429010(into: acc, { $0 + $1 })
  // expected-warning@-1 {{result of operator '+' is unused}}
  let _: Int = AnySequence { iter }.rdar33429010(into: acc, { $0.rdar33429010_incr($1) })
}

class P_33429010 {
  var name: String = "foo"
}

class C_33429010 : P_33429010 {
}

func rdar33429010_3() {
 let arr = [C_33429010()]
 let _ = arr.map({ ($0.name, $0 as P_33429010) }) // Ok
}

func rdar36054961() {
  func bar(dict: [String: (inout String, Range<String.Index>, String) -> Void]) {}
  bar(dict: ["abc": { str, range, _ in
     str.replaceSubrange(range, with: str[range].reversed())
  }])
}

protocol P_37790062 {
  associatedtype T
  var elt: T { get }
}

func rdar37790062() {
  struct S<T> {
    init(_ a: () -> T, _ b: () -> T) {}
  }

  class C1 : P_37790062 {
    typealias T = Int
    var elt: T { return 42 }
  }

  class C2 : P_37790062 {
    typealias T = (String, Int, Void)
    var elt: T { return ("question", 42, ()) }
  }

  func foo() -> Int { return 42 }
  func bar() -> Void {}
  func baz() -> (String, Int) { return ("question", 42) }
  func bzz<T>(_ a: T) -> T { return a }
  func faz<T: P_37790062>(_ a: T) -> T.T { return a.elt }

  _ = S({ foo() }, { bar() }) // expected-warning {{result of call to 'foo()' is unused}}
  _ = S({ baz() }, { bar() }) // expected-warning {{result of call to 'baz()' is unused}}
  _ = S({ bzz(("question", 42)) }, { bar() }) // expected-warning {{result of call to 'bzz' is unused}}
  _ = S({ bzz(String.self) }, { bar() }) // expected-warning {{result of call to 'bzz' is unused}}
  _ = S({ bzz(((), (()))) }, { bar() }) // expected-warning {{result of call to 'bzz' is unused}}
  _ = S({ bzz(C1()) }, { bar() }) // expected-warning {{result of call to 'bzz' is unused}}
  _ = S({ faz(C2()) }, { bar() }) // expected-warning {{result of call to 'faz' is unused}}
}

// <rdar://problem/39489003>
typealias KeyedItem<K, T> = (key: K, value: T)

protocol Node {
  associatedtype T
  associatedtype E
  associatedtype K
  var item: E {get set}
  var children: [(key: K, value: T)] {get set}
}

extension Node {
  func getChild(for key:K)->(key: K, value: T) {
    return children.first(where: { (item:KeyedItem) -> Bool in
        return item.key == key
        // expected-error@-1 {{binary operator '==' cannot be applied to two 'Self.K' operands}}
      })!
  }
}

// Make sure we don't allow this anymore
func takesTwo(_: (Int, Int) -> ()) {}
func takesTwoInOut(_: (Int, inout Int) -> ()) {}

takesTwo { _ in } // expected-error {{contextual closure type '(Int, Int) -> ()' expects 2 arguments, but 1 was used in closure body}}
takesTwoInOut { _ in } // expected-error {{contextual closure type '(Int, inout Int) -> ()' expects 2 arguments, but 1 was used in closure body}}

// <rdar://problem/20371273> Type errors inside anonymous functions don't provide enough information
func f20371273() {
  let x: [Int] = [1, 2, 3, 4]
  let y: UInt = 4
  _ = x.filter { ($0 + y)  > 42 } // expected-error {{cannot convert value of type 'UInt' to expected argument type 'Int'}}
}

// rdar://problem/42337247

func overloaded(_ handler: () -> Int) {} // expected-note {{found this candidate}}
func overloaded(_ handler: () -> Void) {} // expected-note {{found this candidate}}

overloaded { } // empty body => inferred as returning ()

overloaded { print("hi") } // single-expression closure => typechecked with body

overloaded { print("hi"); print("bye") } // multiple expression closure without explicit returns; can default to any return type
// expected-error@-1 {{ambiguous use of 'overloaded'}}

func not_overloaded(_ handler: () -> Int) {}

not_overloaded { } // empty body
// expected-error@-1 {{cannot convert value of type '()' to closure result type 'Int'}}

not_overloaded { print("hi") } // single-expression closure
// expected-error@-1 {{cannot convert value of type '()' to closure result type 'Int'}}

// no error in -typecheck, but dataflow diagnostics will complain about missing return
not_overloaded { print("hi"); print("bye") } // multiple expression closure

func apply(_ fn: (Int) throws -> Int) rethrows -> Int {
  return try fn(0)
}

enum E : Error {
  case E
}

func test() -> Int? {
  return try? apply({ _ in throw E.E })
}

var fn: () -> [Int] = {}
// expected-error@-1 {{cannot convert value of type '[Int]' to closure result type '()'}}

fn = {}
// expected-error@-1 {{cannot assign value of type '() -> ()' to type '() -> [Int]'}}

func test<Instances : Collection>(
  _ instances: Instances,
  _ fn: (Instances.Index, Instances.Index) -> Bool
) { fatalError() }

test([1]) { _, _ in fatalError(); () }

// rdar://problem/40537960 - Misleading diagnostic when using closure with wrong type

protocol P_40537960 {}
func rdar_40537960() {
  struct S {
    var v: String
  }

  struct L : P_40537960 {
    init(_: String) {}
  }

  struct R<T : P_40537960> {
    init(_: P_40537960) {}
  }

  struct A<T: Collection, P: P_40537960> { // expected-note {{'P' declared as parameter to type 'A'}}
    typealias Data = T.Element
    init(_: T, fn: (Data) -> R<P>) {}
  }

  var arr: [S] = []
  _ = A(arr, fn: { L($0.v) })
  // expected-error@-1 {{generic parameter 'P' could not be inferred}}
  // expected-note@-2 {{explicitly specify the generic arguments to fix this issue}} {{8-8=<[S], <#P: P_40537960#>>}}
}

// rdar://problem/45659733
func rdar_45659733() {
  func foo<T : BinaryInteger>(_: AnyHashable, _: T) {}
  func bar(_ a: Int, _ b: Int) {
    _ = (a ..< b).map { i in foo(i, i) } // Ok
  }

  struct S<V> {
    func map<T>(
      get: @escaping (V) -> T,
      set: @escaping (inout V, T) -> Void
    ) -> S<T> {
      fatalError()
    }

    subscript<T>(
      keyPath: WritableKeyPath<V, T?>,
      default defaultValue: T
    ) -> S<T> {
      return map(
        get: { $0[keyPath: keyPath] ?? defaultValue },
        set: { $0[keyPath: keyPath] = $1 }
      ) // Ok, make sure that we deduce result to be S<T>
    }
  }
}

func rdar45771997() {
  struct S {
    mutating func foo() {}
  }

  let _: Int = { (s: inout S) in s.foo() }
  // expected-error@-1 {{cannot convert value of type '(inout S) -> ()' to specified type 'Int'}}
}

struct rdar30347997 {
  func withUnsafeMutableBufferPointer(body : (inout Int) -> ()) {}
  func foo() {
    withUnsafeMutableBufferPointer { // expected-error {{cannot convert value of type '(Int) -> ()' to expected argument type '(inout Int) -> ()'}}
      (b : Int) in
    }
  }
}

struct rdar43866352<Options> {
  func foo() {
    let callback: (inout Options) -> Void
    callback = { (options: Options) in } // expected-error {{cannot assign value of type '(Options) -> ()' to type '(inout Options) -> Void'}}
  }
}

extension Hashable {
  var self_: Self {
    return self
  }
}

do {
  struct S<
      C : Collection,
      I : Hashable,
      R : Numeric
  > {
    init(_ arr: C,
         id: KeyPath<C.Element, I>,
         content: @escaping (C.Element) -> R) {}
  }

  func foo(_ arr: [Int]) {
    _ = S(arr, id: \.self_) {
      // expected-error@-1 {{contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored}} {{30-30=_ in }}
      return 42
    }
  }
}

// Don't allow result type of a closure to end up as a noescape type

// The funny error is because we infer the type of badResult as () -> ()
// via the 'T -> U => T -> ()' implicit conversion.
let badResult = { (fn: () -> ()) in fn }
// expected-error@-1 {{function is unused}}

// rdar://problem/55102498 - closure's result type can't be inferred if the last parameter has a default value
func test_trailing_closure_with_defaulted_last() {
  func foo<T>(fn: () -> T, value: Int = 0) {}
  foo { 42 } // Ok
  foo(fn: { 42 }) // Ok
}

// Test that even in multi-statement closure case we still pick up `(Action) -> Void` over `Optional<(Action) -> Void>`.
// Such behavior used to rely on ranking of partial solutions but with delayed constraint generation of closure bodies
// it's no longer the case, so we need to make sure that even in case of complete solutions we still pick the right type.

protocol Action { }
protocol StateType { }

typealias Fn = (Action) -> Void
typealias Middleware<State> = (@escaping Fn, @escaping () -> State?) -> (@escaping Fn) -> Fn

class Foo<State: StateType> {
  var state: State!
  var fn: Fn!

  init(middleware: [Middleware<State>]) {
    self.fn = middleware
               .reversed()
               .reduce({ action in },
                       { (fun, middleware) in // Ok, to type-check result type has to be `(Action) -> Void`
                         let dispatch: (Action) -> Void = { _ in }
                         let getState = { [weak self] in self?.state }
                         return middleware(dispatch, getState)(fun)
                       })
  }
}

// Make sure that `String...` is translated into `[String]` in the body
func test_explicit_variadic_is_interpreted_correctly() {
  _ = { (T: String...) -> String in T[0] + "" } // Ok
}

// rdar://problem/59208419 - closure result type is incorrectly inferred to be a supertype
func test_correct_inference_of_closure_result_in_presence_of_optionals() {
  class A {}
  class B : A {}

  func foo(_: B) -> Int? { return 42 }

  func bar<T: A>(_: (A) -> T?) -> T? {
    return .none
  }

  guard let v = bar({ $0 as? B }),
        let _ = foo(v) // Ok, v is inferred as `B`
  else {
    return;
  }
}


// rdar://problem/59741308 - inference fails with tuple element has to joined to supertype
func rdar_59741308() {
  class Base {
    func foo(_: Int) {}
  }

  class A : Base {}
  class B : Base {}

  func test() {
    // Note that `0`, and `1` here are going to be type variables
    // which makes join impossible until it's already to late for
    // it to be useful.
    [(A(), 0), (B(), 1)].forEach { base, value in
      base.foo(value) // Ok
    }
  }
}

func r60074136() {
  func takesClosure(_ closure: ((Int) -> Void) -> Void) {}

  takesClosure { ((Int) -> Void) -> Void in // expected-warning {{unnamed parameters must be written with the empty name '_'; this is an error in the Swift 6 language mode}}
  }
}

func rdar52204414() {
  let _: () -> Void = { return 42 }
  // expected-error@-1 {{cannot convert value of type 'Int' to closure result type 'Void'}}
  let _ = { () -> Void in return 42 }
  // expected-error@-1 {{declared closure result 'Void' is incompatible with return type 'Int'}} {{19-23=Int}}
}

// https://github.com/apple/swift/issues/54719
// Trailing closure is used as an argument to the last (positionally) parameter.
//
// Note that this was accepted prior to Swift 5.3. SE-0286 changed the
// order of argument resolution and made it ambiguous.

func overloaded_with_default(a: () -> Int, b: Int = 0, c: Int = 0) {} // expected-note{{found this candidate}}
func overloaded_with_default(b: Int = 0, c: Int = 0, a: () -> Int) {} // expected-note{{found this candidate}}

overloaded_with_default { 0 } // expected-error{{ambiguous use of 'overloaded_with_default'}}

func overloaded_with_default_and_autoclosure<T>(_ a: @autoclosure () -> T, b: Int = 0) {}
func overloaded_with_default_and_autoclosure<T>(b: Int = 0, c: @escaping () -> T?) {}

overloaded_with_default_and_autoclosure { 42 } // Ok
overloaded_with_default_and_autoclosure(42) // Ok

/// https://github.com/apple/swift/issues/55261
/// "error: type of expression is ambiguous without a type annotation" in many cases
/// where methods are missing.
do {
  let _ = { a, b in }
  // expected-error@-1 {{cannot infer type of closure parameter 'a' without a type annotation}}
  // expected-error@-2 {{cannot infer type of closure parameter 'b' without a type annotation}}

  _ = .a { b in } // expected-error {{cannot infer contextual base in reference to member 'a'}}

  struct S {}

  func test(s: S) {
    S.doesntExist { b in } // expected-error {{type 'S' has no member 'doesntExist'}}
    s.doesntExist { b in } // expected-error {{value of type 'S' has no member 'doesntExist'}}
    s.doesntExist1 { v in } // expected-error {{value of type 'S' has no member 'doesntExist1'}}
     .doesntExist2() { $0 }
  }
}

// Make sure we can infer generic arguments in an explicit result type.
let explicitUnboundResult1 = { () -> Array in [0] }
let explicitUnboundResult2: (Array<Bool>) -> Array<Int> = {
  (arr: Array) -> Array in [0]
}
// FIXME: Should we prioritize the contextual result type and infer Array<Int>
// rather than using a type variable in these cases?
// expected-error@+1 {{unable to infer closure type without a type annotation}}
let explicitUnboundResult3: (Array<Bool>) -> Array<Int> = {
  (arr: Array) -> Array in [true]
}

// rdar://problem/71525503 - Assertion failed: (!shouldHaveDirectCalleeOverload(call) && "Should we have resolved a callee for this?")
func test_inout_with_invalid_member_ref() {
  struct S {
    static func createS(_ arg: inout Int) -> S { S() }
  }
  class C {
    static subscript(s: (Int) -> Void) -> Bool { get { return false } }
  }

  let _: Bool = C[{ .createS(&$0) }]
  // expected-error@-1 {{value of tuple type 'Void' has no member 'createS'}}
  // expected-error@-2 {{cannot pass immutable value as inout argument: '$0' is immutable}}
}

// rdar://problem/74435602 - failure to infer a type for @autoclosure parameter.
func rdar_74435602(error: Error?) {
  func accepts_autoclosure<T>(_ expression: @autoclosure () throws -> T) {}

  accepts_autoclosure({
    if let failure = error {
      throw failure
    }
  })
}

// https://github.com/apple/swift/issues/56639

let _: (@convention(block) () -> Void)? = Bool.random() ? nil : {} // OK
let _: (@convention(thin) () -> Void)? = Bool.random() ? nil : {} // OK
let _: (@convention(c) () -> Void)? = Bool.random() ? nil : {} // OK on type checking, diagnostics are deferred to SIL

let _: (@convention(block) () -> Void)? = Bool.random() ? {} : {} // OK
let _: (@convention(thin) () -> Void)? = Bool.random() ? {} : {} // OK
let _: (@convention(c) () -> Void)? = Bool.random() ? {} : {} // OK on type checking, diagnostics are deferred to SIL

// Make sure that diagnostic is attached to the closure even when body is empty (implicitly returns `Void`)
var emptyBodyMismatch: () -> Int {
  return { // expected-error {{cannot convert value of type '()' to closure result type 'Int'}}
    return
  }
}

// rdar://76250381 - crash when passing an argument to a closure that takes no arguments
struct R_76250381<Result, Failure: Error> {
  func test(operation: @escaping () -> Result) -> Bool {
    return try self.crash { group in // expected-error {{contextual closure type '() -> Result' expects 0 arguments, but 1 was used in closure body}}
      operation(&group) // expected-error {{argument passed to call that takes no arguments}}
    }
  }

  func crash(_: @escaping () -> Result) -> Bool {
    return false
  }
}

// https://github.com/apple/swift/issues/55926
(0..<10).map { x, y in } 
// expected-error@-1 {{contextual closure type '(Range<Int>.Element) -> ()' (aka '(Int) -> ()') expects 1 argument, but 2 were used in closure body}}
(0..<10).map { x, y, z in } 
// expected-error@-1 {{contextual closure type '(Range<Int>.Element) -> ()' (aka '(Int) -> ()') expects 1 argument, but 3 were used in closure body}}
(0..<10).map { x, y, z, w in } 
// expected-error@-1 {{contextual closure type '(Range<Int>.Element) -> ()' (aka '(Int) -> ()') expects 1 argument, but 4 were used in closure body}}

// rdar://77022842 - crash due to a missing argument to a ternary operator
func rdar77022842(argA: Bool? = nil, argB: Bool? = nil) {
  if let a = argA ?? false, if let b = argB ?? {
    // expected-error@-1 {{initializer for conditional binding must have Optional type, not 'Bool'}}
    // expected-error@-2 {{cannot convert value of type 'Bool?' to expected argument type '(() -> ())?'}}
    // expected-error@-3 {{cannot convert value of type 'Void' to expected condition type 'Bool'}}
    // expected-error@-4 {{'if' may only be used as expression in return, throw, or as the source of an assignment}}
    // expected-error@-5 {{'if' must have an unconditional 'else' to be used as expression}}
  } // expected-error {{expected '{' after 'if' condition}}
}

// rdar://76058892 - spurious ambiguity diagnostic
func rdar76058892() {
  struct S {
    var test: Int = 0
  }

  func test(_: Int) {}
  func test(_: () -> String) {}

  func experiment(arr: [S]?) {
    test { // expected-error {{contextual closure type '() -> String' expects 0 arguments, but 1 was used in closure body}}
      if let arr = arr {
        arr.map($0.test) // expected-note {{anonymous closure parameter '$0' is used here}} // expected-error {{generic parameter 'T' could not be inferred}}
        // expected-error@-1 {{generic parameter 'E' could not be inferred}}
      }
    }
  }
}

// rdar://78917861 - Invalid generic type parameter inference

func rdar78917861() {
  class Cell {}
  class MyCell : Cell {}

  class DataCollection<D, C: Cell> {
  }

  class MyCollection {
    typealias DataType = String
    typealias CellType = MyCell

    var data: DataCollection<DataType, CellType>

    init() {
      self.data = DataCollection<DataType, CellType>()
    }
  }

  class Test {
    let collection = MyCollection()

    lazy var prop: DataCollection = {
      collection.data // Ok
      // Since contextual type `DataCollection` doesn't specify generic parameters they have to be inferred
      // but that has to wait until the closure is resolved because types can flow both ways
    }()
  }
}

// rdar://81228501 - type-checker crash due to applied invalid solution
func test(arr: [[Int]]) {
  struct A {
    init(arg: [Int]) {}
  }

  arr.map { ($0 as? [Int]).map { A($0) } } // expected-error {{missing argument label 'arg:' in call}} {{36-36=arg: }}
}

func closureWithCaseArchetype<T>(_: T.Type) {
  let _ = { (any: Any) throws -> Any? in
    switch any {
    case let type as T:
      return type

    default:
      return any
    }
  }
}

// rdar://112426330 - invalid diagnostic when closure argument is omitted
do {
  func test<T>(_: T, _: (T) -> Void) {}

  test(42) { // expected-error {{contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored}} {{13-13= _ in}}
    print("")
  }

  func context(_: (Int) -> Void) {}
  func context(_: () -> Void) {}

  context {
    test(42) { // expected-error {{contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored}} {{15-15= _ in}}
      print("")
    }
  }


}

do {
  func test(_: Int, _: Int) {}
  // expected-note@-1 {{closure passed to parameter of type 'Int' that does not accept a closure}}
  func test(_: Int, _: String) {}
  // expected-note@-1 {{closure passed to parameter of type 'String' that does not accept a closure}}

  test(42) { // expected-error {{no exact matches in call to local function 'test'}}
    print($0)
  }
}

// Currently legal.
let _: () -> Int = { return fatalError() }

// Make sure that `Void` assigned to closure result doesn't get eagerly propagated into the body
do {
  class C {
    func f(_: Any) -> Int! { fatalError() }
    static func f(_: Any) -> Int! { fatalError() }
  }

  class G<T> {
    func g<U>(_ u: U, _: (U, T) -> ()) {}

    func g<U: C>(_ u: U) {
        g(u) { $0.f($1) } // expected-warning {{result of call to 'f' is unused}}
    }
  }
}

// Make sure that closure gets both Void? and Void attempted
// otherwise it won't be possible to type-check the second closure.
do {
  struct Semaphore {
    func signal() -> Int {}
  }

  func compute(_ completion: (Semaphore?) -> Void?) {}

  func test() {
    compute { $0?.signal() }
    // expected-warning@-1 {{result of call to 'signal()' is unused}}

    true
      ? compute({ $0?.signal() }) // expected-warning {{result of call to 'signal()' is unused}}
      : compute({
           let sem = $0!
           sem.signal() // expected-warning {{result of call to 'signal()' is unused}}
        })
  }
}

// rdar://143474313 - invalid error: member 'init(item:)' in 'Test.Item?' produces result of type 'Test.Item', but context expects 'Test.Item?'
do {
  struct List {
    struct Item {
    }

    var items: [Item] = []
  }

  struct Test {
    struct Item {
      init(item: List.Item) {
      }
    }

    let list: List

    var items: [Test.Item] { .init(list.items.compactMap { .init(item: $0) }) } // Ok
  }
}

// This should type check
func rdar143338891() {
  func takesAny(_: Any?) {}

  class Test {
    func test() {
      _ = { [weak self] in takesAny(self) }
    }
  }
}

do {
  struct V {
    init(value: @autoclosure @escaping () -> any Hashable) { }
    init(other: @autoclosure @escaping () -> String) { }
  }

  let _ = V(value: { [Int]() }) // expected-error {{add () to forward '@autoclosure' parameter}} {{31-31=()}}
  let _ = V(other: { [Int]() }) // expected-error {{cannot convert value of type '[Int]' to closure result type 'String'}}
}

// https://github.com/swiftlang/swift/issues/81770
do {
  func test(_: Int) {}
  func test(_: Int = 42, _: (Int) -> Void) {}

  test {
    if let _ = $0.missing { // expected-error {{value of type 'Int' has no member 'missing'}}
    }
  }

  test {
    if let _ = (($0.missing)) { // expected-error {{value of type 'Int' has no member 'missing'}}
    }
  }

  test { // expected-error {{invalid conversion from throwing function of type '(Int) throws -> Void' to non-throwing function type '(Int) -> Void'}}
    try $0.missing // expected-error {{value of type 'Int' has no member 'missing'}}
  }
}

// Generic requirement failures associated with closure parameters should be diagnosed.
protocol Input {
  associatedtype Value
  var value: Value { get }
}

protocol Idable {
  associatedtype ID
}

struct TestInput<ItemID: Hashable, Value: Collection<ItemID>> : Input { // expected-note {{where 'Value' = 'Item.ID'}}
  var value: Value
}

struct Container<I: Input> {
  var data: (I) -> Void
}

func test_generic_closure_parameter_requirement_failure<Item: Idable>(
  for itemType: Item.Type = Item.self,
  _ payload: @escaping (_ itemID: Item.ID) -> Void
) where Item.ID : Sendable {
  Container(data: { (input: TestInput) in payload(input.value) })
  // expected-error@-1 {{generic struct 'TestInput' requires that 'Item.ID' conform to 'Collection'}}
}

// Since implicit result implies `()` it should be allowed to be converted to e.g. `Void` and `Any`
func test_implicit_result_conversions() {
  func test_optional(_ x: Int) {
    let _: Any? = {
      switch x {
      case 0:
        return 1
      default:
        return
      }
    }()
  }

  func testAny(_: () -> Any) {}

  testAny { } // Ok
  testAny { return } // Ok
  testAny {
    _ = 42
    return // Ok
  }
}
