Merge pull request #21777 from hvitved/swift/type-inference-tests

Swift: Add type inference tests

swift/ql/test/library-tests/type-inference/basics.swift

@@ -0,0 +1,71 @@
+var topLevelDecl : Int = 0
+0
+topLevelDecl + 1 // $ type=topLevelDecl:Int
+
+class C {
+  var myInt : Int
+  // C.init
+  init(n: Int) {
+    myInt = n // $ type=n:Int
+  }
+
+  // C.getMyInt
+  func getMyInt() -> Int {
+    return myInt // $ type=.myInt:Int
+  }
+}
+
+class Derived : C {
+  // Derived.init
+  init() {
+    super.init(n: 0) // $ type=super:C target=C.init
+  }
+
+  // Derived.callGetMyInt
+  func callGetMyInt() -> Int {
+    let x = getMyInt(); // $ type=x:Int target=C.getMyInt
+    return x
+  }
+}
+
+class Generic<T> {
+  var value : T
+  // Generic.init
+  init(v: T) {
+    value = v // $ type=v:T
+  }
+
+  // Generic.getValue
+  func getValue() -> T {
+    return value // $ type=.value:T
+  }
+}
+
+class GenericDerived : Generic<Int> {
+  // GenericDerived.init
+  init() {
+    super.init(v: 0) // $ type=super@Generic<T>:Int target=Generic.init
+  }
+}
+
+func testGeneric() {
+  let g = Generic(v: 42) // $ type=g@Generic<T>:Int target=Generic.init
+  let x = g.getValue() // $ type=x:Int target=Generic.getValue
+
+  let gd = GenericDerived() // $ type=gd:GenericDerived target=GenericDerived.init
+  let y = gd.getValue() // $ type=y:Int target=Generic.getValue
+}
+
+// --- Extensions ---
+
+extension C {
+  // C.doubled
+  func doubled() -> Int {
+    return myInt * 2 // $ type=.myInt:Int
+  }
+}
+
+func testExtension() {
+  let obj = C(n: 10) // $ target=C.init
+  let d = obj.doubled() // $ type=d:Int target=C.doubled
+}

swift/ql/test/library-tests/type-inference/classes.swift

@@ -0,0 +1,231 @@
+// --- Static methods ---
+
+class MathUtils {
+  // MathUtils.square
+  static func square(x: Int) -> Int {
+    return x * x // $ type=x:Int
+  }
+
+  // MathUtils.cube
+  class func cube(x: Int) -> Int {
+    return x * x * x // $ type=x:Int
+  }
+}
+
+func testStaticMethods() {
+  let s = MathUtils.square(x: 4) // $ type=s:Int target=MathUtils.square
+  let cu = MathUtils.cube(x: 3) // $ type=cu:Int target=MathUtils.cube
+}
+
+// --- Simple overloading ---
+
+class Overloaded {
+  // Overloaded.process(_:Int)
+  func process(_ x: Int) -> Int {
+    return x + 1 // $ type=x:Int
+  }
+
+  // Overloaded.process(_:String)
+  func process(_ s: String) -> String {
+    return s // $ type=s:String
+  }
+}
+
+func testOverloading() {
+  let o = Overloaded() // $ target=init()
+  let r1 = o.process(42) // $ type=r1:Int target=Overloaded.process(_:Int)
+  let r2 = o.process("hello") // $ type=r2:String target=Overloaded.process(_:String)
+}
+
+// --- Structs and methods ---
+
+struct Matrix {
+  var data : [[Int]]
+
+  // Matrix.init
+  init(data: [[Int]]) {
+    self.data = data
+  }
+
+  // Matrix.rowCount
+  func rowCount() -> Int {
+    return data.count
+  }
+}
+
+func testSubscripts() {
+  let m = Matrix(data: [[1, 2], [3, 4]]) // $ target=Matrix.init
+  let rc = m.rowCount() // $ type=rc:Int target=Matrix.rowCount
+}
+
+// --- Nested types ---
+
+class Outer {
+  class Inner {
+    var value : Int
+
+    // Outer.Inner.init
+    init(value: Int) {
+      self.value = value // $ type=value:Int
+    }
+
+    // Outer.Inner.getValue
+    func getValue() -> Int {
+      return self.value // $ type=.value:Int
+    }
+  }
+}
+
+func testNestedTypes() {
+  let inner = Outer.Inner(value: 99) // $ type=inner:Inner target=Outer.Inner.init
+  let v = inner.getValue() // $ type=v:Int target=Outer.Inner.getValue
+}
+
+// --- Method chaining ---
+
+class Builder {
+  var value : Int = 0
+
+  // Builder.init
+  init() {}
+
+  // Builder.set
+  func set(_ v: Int) -> Builder {
+    value = v
+    return self
+  }
+
+  // Builder.add
+  func add(_ v: Int) -> Builder {
+    value += v
+    return self
+  }
+
+  // Builder.build
+  func build() -> Int {
+    return value // $ type=.value:Int
+  }
+}
+
+func testChaining() {
+  let b = Builder() // $ type=b:Builder target=Builder.init
+  let result = b.set(10).add(5).build() // $ type=result:Int target=Builder.set target=Builder.add target=Builder.build
+}
+
+// --- Default parameter values ---
+
+class Config {
+  // Config.init
+  init() {}
+
+  // Config.setup
+  func setup(retries: Int = 3, timeout: Double = 30.0) -> Int {
+    return retries // $ type=retries:Int
+  }
+}
+
+func testDefaultParams() {
+  let cfg = Config() // $ type=cfg:Config target=Config.init
+  let r1 = cfg.setup() // $ type=r1:Int target=Config.setup
+  let r2 = cfg.setup(retries: 5) // $ type=r2:Int target=Config.setup
+  let r3 = cfg.setup(retries: 2, timeout: 60.0) // $ type=r3:Int target=Config.setup
+}
+
+// --- Computed properties accessed via methods ---
+
+class Temperature {
+  var celsius : Double
+
+  // Temperature.init
+  init(celsius: Double) {
+    self.celsius = celsius // $ type=celsius:Double
+  }
+
+  // Temperature.toCelsius
+  func toCelsius() -> Double {
+    return celsius // $ type=.celsius:Double
+  }
+
+  // Temperature.toFahrenheit
+  func toFahrenheit() -> Double {
+    return celsius * 9.0 / 5.0 + 32.0 // $ type=.celsius:Double
+  }
+}
+
+func testTemperature() {
+  let t = Temperature(celsius: 100.0) // $ type=t:Temperature target=Temperature.init
+  let c = t.toCelsius() // $ type=c:Double target=Temperature.toCelsius
+  let f = t.toFahrenheit() // $ type=f:Double target=Temperature.toFahrenheit
+}
+
+// --- Inheritance with overriding ---
+
+class Animal {
+  // Animal.init
+  init() {}
+
+  // Animal.speak
+  func speak() -> String {
+    return "..."
+  }
+}
+
+class Dog : Animal {
+  // Dog.init
+  override init() {
+    super.init() // $ target=Animal.init
+  }
+
+  // Dog.speak
+  override func speak() -> String {
+    return "Woof"
+  }
+
+  // Dog.fetch
+  func fetch() -> String {
+    return "ball"
+  }
+}
+
+class Cat : Animal {
+  // Cat.init
+  override init() {
+    super.init() // $ target=Animal.init
+  }
+
+  // Cat.speak
+  override func speak() -> String {
+    return "Meow"
+  }
+}
+
+func testOverriding() {
+  let d = Dog() // $ type=d:Dog target=Dog.init
+  let ds = d.speak() // $ type=ds:String target=Dog.speak
+  let df = d.fetch() // $ type=df:String target=Dog.fetch
+
+  let ct = Cat() // $ type=ct:Cat target=Cat.init
+  let cs = ct.speak() // $ type=cs:String target=Cat.speak
+}
+
+// --- Mutating methods on structs ---
+
+struct Counter {
+  var count : Int = 0
+
+  // Counter.increment
+  mutating func increment() {
+    count += 1
+  }
+
+  // Counter.getCount
+  func getCount() -> Int {
+    return count // $ type=.count:Int
+  }
+}
+
+func testMutating() {
+  var ctr = Counter() // $ type=ctr:Counter target=init()
+  ctr.increment() // $ target=Counter.increment
+  let val = ctr.getCount() // $ type=val:Int target=Counter.getCount
+}

swift/ql/test/library-tests/type-inference/generics.swift

@@ -0,0 +1,143 @@
+// --- Generic functions ---
+
+// identity
+func identity<T>(_ x: T) -> T {
+  return x // $ type=x:T
+}
+
+// makePair
+func makePair<A, B>(_ a: A, _ b: B) -> (A, B) {
+  return (a, b) // $ type=a:A
+}
+
+func testGenericFunctions() {
+  let i = identity(42) // $ type=i:Int target=identity
+  let s = identity("hello") // $ type=s:String target=identity
+  let p = makePair(1, "two") // $ target=makePair
+}
+
+// --- Generic structs ---
+
+struct Pair<A, B> {
+  var first : A
+  var second : B
+
+  // Pair.init
+  init(first: A, second: B) {
+    self.first = first // $ type=first:A
+    self.second = second // $ type=second:B
+  }
+
+  // Pair.getFirst
+  func getFirst() -> A {
+    return first // $ type=.first:A
+  }
+
+  // Pair.getSecond
+  func getSecond() -> B {
+    return second // $ type=.second:B
+  }
+}
+
+func testGenericStruct() {
+  let p = Pair(first: 1, second: "x") // $ target=Pair.init type=p@Pair<A>:Int type=p@Pair<B>:String
+  let f = p.getFirst() // $ type=f:Int target=Pair.getFirst
+  let sc = p.getSecond() // $ type=sc:String target=Pair.getSecond
+}
+
+// --- Enums with associated values ---
+
+enum Result<T> {
+  // Result.success
+  case success(T)
+  // Result.failure
+  case failure(String)
+
+  // Result.getValue
+  func getValue() -> T? {
+    switch self {
+    case .success(let v): // $ target=Result.success
+      return v // $ type=v:T
+    case .failure: // $ target=Result.failure
+      return nil
+    }
+  }
+}
+
+func testEnum() {
+  let r = Result.success(42) // $ type=r@Result<T>:Int target=Result.success
+  let v = r.getValue() // $ target=Result.getValue
+
+  let r2 : Result<Int> = .success(42) // $ type=r2@Result<T>:Int target=Result.success
+  let v2 = r2.getValue() // $ target=Result.getValue
+}
+
+// --- Closures and type inference ---
+
+// applyTransform
+func applyTransform<T, U>(_ value: T, _ transform: (T) -> U) -> U {
+  return transform(value)
+}
+
+func testClosures() {
+  let result = applyTransform(5, { x in x * 2 }) // $ target=applyTransform type=result:Int
+  let strings = applyTransform(10, { x in String(x) }) // $ target=applyTransform type=strings:String
+}
+
+// --- Generic class with constraints ---
+
+protocol MyProtocol {
+  associatedtype MyType
+
+  // MyProtocol.foo
+  func foo() -> Self
+
+  // MyProtocol.bar
+  func bar() -> MyType
+}
+
+class Wrapper<T: MyProtocol> {
+  var inner : T
+
+  // Wrapper.init
+  init(_ inner: T) {
+    self.inner = inner // $ type=inner:T
+  }
+
+  // Wrapper.get
+  func get() -> T {
+    return inner // $ type=.inner:T
+  }
+
+  // Wrapper.callFoo
+  func callFoo() -> T {
+    let x = inner.foo(); // $ type=x:T target=MyProtocol.foo
+    return x
+  }
+
+  // Wrapper.callBar
+  func callBar() -> T.MyType {
+    let x = inner.bar(); // $ type=x:MyType target=MyProtocol.bar
+    return x
+  }
+}
+
+extension Int : MyProtocol {
+  typealias MyType = String
+  
+  // Int.foo
+  func foo() -> Int {
+    return self * 2 // $ type=self:Int
+  }
+
+  // Int.bar
+  func bar() -> String {
+    return "number"
+  }
+}
+
+func testConstrainedGeneric() {
+  let w = Wrapper(42) // $ type=w@Wrapper<T>:Int target=Wrapper.init
+  let v = w.get() // $ type=v:Int target=Wrapper.get
+  let z = w.callFoo() // $ type=z:Int target=Wrapper.callFoo
+}

swift/ql/test/library-tests/type-inference/key_paths.swift

@@ -0,0 +1,220 @@
+// --- Key-path expressions: basic property access ---
+
+struct Point {
+  var x : Double
+  var y : Double
+
+  // Point.init
+  init(x: Double, y: Double) {
+    self.x = x // $ type=x:Double
+    self.y = y // $ type=y:Double
+  }
+
+  // Point.distanceFromOrigin
+  func distanceFromOrigin() -> Double {
+    return (x * x + y * y).squareRoot()
+  }
+}
+
+struct Line {
+  var start : Point
+  var end : Point
+
+  // Line.init
+  init(start: Point, end: Point) {
+    self.start = start
+    self.end = end
+  }
+}
+
+func testBasicKeyPaths() {
+  let kpX = \Point.x
+  let kpY = \Point.y
+
+  let p = Point(x: 3.0, y: 4.0) // $ type=p:Point target=Point.init
+  let xVal = p[keyPath: kpX] // $ type=xVal:Double
+  let yVal = p[keyPath: kpY] // $ type=yVal:Double
+}
+
+// --- Key-path expressions: nested property access ---
+
+func testNestedKeyPaths() {
+  let kpStartX = \Line.start.x
+  let kpEndY = \Line.end.y
+
+  let s = Point(x: 0.0, y: 0.0) // $ target=Point.init
+  let e = Point(x: 1.0, y: 1.0) // $ target=Point.init
+  let line = Line(start: s, end: e) // $ target=Line.init
+  let startX = line[keyPath: kpStartX] // $ type=startX:Double
+  let endY = line[keyPath: kpEndY] // $ type=endY:Double
+}
+
+// --- Key-path expressions: identity (\.self) ---
+
+func testSelfKeyPath() {
+  let kpSelf = \Int.self
+  let val = 42[keyPath: kpSelf] // $ type=val:Int
+}
+
+// --- Key-path expressions: optional chaining ---
+
+struct Person {
+  var name : String
+  var address : Address?
+
+  // Person.init
+  init(name: String, address: Address?) {
+    self.name = name // $ type=name:String
+    self.address = address
+  }
+}
+
+struct Address {
+  var city : String
+  var zip : String
+
+  // Address.init
+  init(city: String, zip: String) {
+    self.city = city // $ type=city:String
+    self.zip = zip // $ type=zip:String
+  }
+}
+
+func testOptionalChainingKeyPaths() {
+  let kpCity = \Person.address?.city
+  let addr = Address(city: "NYC", zip: "10001") // $ target=Address.init
+  let person = Person(name: "Alice", address: addr) // $ target=Person.init
+
+  let city = person[keyPath: kpCity] // $ type=city:String?
+}
+
+// --- Key-path expressions: used as function arguments ---
+
+struct Employee {
+  var name : String
+  var salary : Int
+
+  // Employee.init
+  init(name: String, salary: Int) {
+    self.name = name // $ type=name:String
+    self.salary = salary // $ type=salary:Int
+  }
+}
+
+// extractField(_:keyPath:)
+func extractField<T, V>(_ items: [T], keyPath: KeyPath<T, V>) -> [V] {
+  return items.map { $0[keyPath: keyPath] }
+}
+
+func testKeyPathAsArgument() {
+  let e1 = Employee(name: "Alice", salary: 100) // $ target=Employee.init
+  let e2 = Employee(name: "Bob", salary: 200) // $ target=Employee.init
+  let employees = [e1, e2]
+  let names = extractField(employees, keyPath: \.name) // $ target=extractField(_:keyPath:)
+  let name = names[0] // $ type=name:String
+  let salaries = extractField(employees, keyPath: \.salary) // $ target=extractField(_:keyPath:)
+  let salary = salaries[0] // $ type=salary:Int
+}
+
+// --- Key-path expressions: with generics ---
+
+class KPContainer<T> {
+  var item : T
+
+  // KPContainer.init
+  init(item: T) {
+    self.item = item // $ type=item:T
+  }
+}
+
+func testGenericKeyPaths() {
+  let kp = \KPContainer<Int>.item
+  let c = KPContainer(item: 42) // $ target=KPContainer.init
+  let v = c[keyPath: kp] // $ type=v:Int
+}
+
+// --- Key-path expressions: writable key paths and mutation ---
+
+func testWritableKeyPaths() {
+  var p = Point(x: 1.0, y: 2.0) // $ type=p:Point target=Point.init
+  let kpX = \Point.x
+  p[keyPath: kpX] = 10.0
+  let newX = p[keyPath: kpX] // $ type=newX:Double
+}
+
+// --- Key-path expressions: appending key paths ---
+
+func testKeyPathAppending() {
+  let kpStart = \Line.start
+  let kpX = \Point.x
+  let kpStartX = kpStart.appending(path: kpX)
+
+  let s = Point(x: 5.0, y: 6.0) // $ target=Point.init
+  let e = Point(x: 7.0, y: 8.0) // $ target=Point.init
+  let line = Line(start: s, end: e) // $ target=Line.init
+  let val = line[keyPath: kpStartX] // $ type=val:Double
+}
+
+// --- Key-path expressions: shorthand in higher-order functions ---
+
+func testKeyPathInMap() {
+  let e1 = Employee(name: "Alice", salary: 100) // $ target=Employee.init
+  let e2 = Employee(name: "Bob", salary: 200) // $ target=Employee.init
+  let employees = [e1, e2]
+  let names = employees.map(\.name)
+  let name = names[0] // $ type=name:String
+  let salaries = employees.map(\.salary)
+  let salary = salaries[0] // $ type=salary:Int
+}
+
+// --- Key-path expressions: class hierarchy ---
+
+class Shape2 {
+  var color : String
+
+  // Shape2.init
+  init(color: String) {
+    self.color = color // $ type=color:String
+  }
+}
+
+class Circle2 : Shape2 {
+  var radius : Double
+
+  // Circle2.init
+  init(color: String, radius: Double) {
+    self.radius = radius // $ type=radius:Double
+    super.init(color: color) // $ target=Shape2.init
+  }
+}
+
+func testInheritedKeyPaths() {
+  let kpColor = \Circle2.color
+  let kpRadius = \Circle2.radius
+
+  let c = Circle2(color: "red", radius: 5.0) // $ type=c:Circle2 target=Circle2.init
+  let col = c[keyPath: kpColor] // $ type=col:String
+  let rad = c[keyPath: kpRadius] // $ type=rad:Double
+}
+
+// --- Key-path expressions: tuple element access ---
+
+func testTupleKeyPath() {
+  let kp0 = \(Int, String).0
+  let kp1 = \(Int, String).1
+  let tuple = (42, "hello")
+  let first = tuple[keyPath: kp0] // $ type=first:Int
+  let second = tuple[keyPath: kp1] // $ type=second:String
+}
+
+// --- Key-path expressions: array/dictionary subscript ---
+
+func testSubscriptKeyPaths() {
+  let kpFirst = \[Int][0]
+  let arr = [10, 20, 30]
+  let first = arr[keyPath: kpFirst] // $ type=first:Int
+
+  let kpKey = \[String: Int]["x"]
+  let dict = ["x": 1, "y": 2]
+  let val = dict[keyPath: kpKey] // $ type=val:Int?
+}

swift/ql/test/library-tests/type-inference/overload_resolution.swift

@@ -0,0 +1,495 @@
+// --- Overload by parameter type ---
+
+class OverloadByType {
+  // OverloadByType.handle(_:Int)
+  func handle(_ x: Int) -> String {
+    return "int"
+  }
+
+  // OverloadByType.handle(_:Double)
+  func handle(_ x: Double) -> String {
+    return "double"
+  }
+
+  // OverloadByType.handle(_:String)
+  func handle(_ x: String) -> String {
+    return "string"
+  }
+
+  // OverloadByType.handle(_:Bool)
+  func handle(_ x: Bool) -> String {
+    return "bool"
+  }
+}
+
+func testOverloadByType() {
+  let o = OverloadByType() // $ target=init()
+  let r1 = o.handle(42) // $ type=r1:String target=OverloadByType.handle(_:Int)
+  let r2 = o.handle(3.14) // $ type=r2:String target=OverloadByType.handle(_:Double)
+  let r3 = o.handle("hi") // $ type=r3:String target=OverloadByType.handle(_:String)
+  let r4 = o.handle(true) // $ type=r4:String target=OverloadByType.handle(_:Bool)
+}
+
+// --- Overload by argument label ---
+
+class OverloadByLabel {
+  // OverloadByLabel.configure(width:)
+  func configure(width: Int) -> String {
+    return "width"
+  }
+
+  // OverloadByLabel.configure(height:)
+  func configure(height: Int) -> String {
+    return "height"
+  }
+
+  // OverloadByLabel.configure(width:height:)
+  func configure(width: Int, height: Int) -> String {
+    return "both"
+  }
+
+  // OverloadByLabel.configure(size:)
+  func configure(size: Int) -> String {
+    return "size"
+  }
+}
+
+func testOverloadByLabel() {
+  let o = OverloadByLabel() // $ target=init()
+  let r1 = o.configure(width: 10) // $ type=r1:String target=OverloadByLabel.configure(width:)
+  let r2 = o.configure(height: 20) // $ type=r2:String target=OverloadByLabel.configure(height:)
+  let r3 = o.configure(width: 10, height: 20) // $ type=r3:String target=OverloadByLabel.configure(width:height:)
+  let r4 = o.configure(size: 30) // $ type=r4:String target=OverloadByLabel.configure(size:)
+}
+
+// --- Overload by arity (number of parameters) ---
+
+class OverloadByArity {
+  // OverloadByArity.compute()
+  func compute() -> Int {
+    return 0
+  }
+
+  // OverloadByArity.compute(_:Int)
+  func compute(_ x: Int) -> Int {
+    return x
+  }
+
+  // OverloadByArity.compute(_:Int,_:Int)
+  func compute(_ x: Int, _ y: Int) -> Int {
+    return x + y
+  }
+
+  // OverloadByArity.compute(_:Int,_:Int,_:Int)
+  func compute(_ x: Int, _ y: Int, _ z: Int) -> Int {
+    return x + y + z
+  }
+}
+
+func testOverloadByArity() {
+  let o = OverloadByArity() // $ target=init()
+  let r0 = o.compute() // $ type=r0:Int target=OverloadByArity.compute()
+  let r1 = o.compute(1) // $ type=r1:Int target=OverloadByArity.compute(_:Int)
+  let r2 = o.compute(1, 2) // $ type=r2:Int target=OverloadByArity.compute(_:Int,_:Int)
+  let r3 = o.compute(1, 2, 3) // $ type=r3:Int target=OverloadByArity.compute(_:Int,_:Int,_:Int)
+}
+
+// --- Overload by return type (contextual type) ---
+
+class OverloadByReturn {
+  // OverloadByReturn.create()->Int
+  func create() -> Int {
+    return 0
+  }
+
+  // OverloadByReturn.create()->String
+  func create() -> String {
+    return ""
+  }
+
+  // OverloadByReturn.create()->Double
+  func create() -> Double {
+    return 0.0
+  }
+}
+
+func testOverloadByReturn() {
+  let o = OverloadByReturn() // $ target=init()
+  let r1 : Int = o.create() // $ type=r1:Int target=OverloadByReturn.create()->Int
+  let r2 : String = o.create() // $ type=r2:String target=OverloadByReturn.create()->String
+  let r3 : Double = o.create() // $ type=r3:Double target=OverloadByReturn.create()->Double
+}
+
+// --- Overload: generic vs non-generic (non-generic preferred) ---
+
+class OverloadGenericVsConcrete {
+  // OverloadGenericVsConcrete.process(_:Int)
+  func process(_ x: Int) -> String {
+    return "concrete"
+  }
+
+  // OverloadGenericVsConcrete.process<T>(_:)
+  func process<T>(_ x: T) -> String {
+    return "generic"
+  }
+}
+
+func testOverloadGenericVsConcrete() {
+  let o = OverloadGenericVsConcrete() // $ target=init()
+  let r1 = o.process(42) // $ type=r1:String target=OverloadGenericVsConcrete.process(_:Int)
+  let r2 = o.process("hello") // $ type=r2:String target=OverloadGenericVsConcrete.process<T>(_:)
+  let r3 = o.process(true) // $ type=r3:String target=OverloadGenericVsConcrete.process<T>(_:)
+}
+
+// --- Overload: free functions by parameter type ---
+
+// freeOverload(_:Int)
+func freeOverload(_ x: Int) -> String {
+  return "int"
+}
+
+// freeOverload(_:String)
+func freeOverload(_ x: String) -> String {
+  return "string"
+}
+
+// freeOverload(_:Double)
+func freeOverload(_ x: Double) -> String {
+  return "double"
+}
+
+func testFreeOverload() {
+  let r1 = freeOverload(42) // $ type=r1:String target=freeOverload(_:Int)
+  let r2 = freeOverload("hi") // $ type=r2:String target=freeOverload(_:String)
+  let r3 = freeOverload(1.5) // $ type=r3:String target=freeOverload(_:Double)
+}
+
+// --- Overload: init overloading ---
+
+class MultiInit {
+  var value : String
+
+  // MultiInit.init()
+  init() {
+    value = "default"
+  }
+
+  // MultiInit.init(int:)
+  init(int: Int) {
+    value = "int"
+  }
+
+  // MultiInit.init(str:)
+  init(str: String) {
+    value = str // $ type=str:String
+  }
+
+  // MultiInit.init(x:y:)
+  init(x: Int, y: Int) {
+    value = "pair"
+  }
+
+  // MultiInit.getValue
+  func getValue() -> String {
+    return value // $ type=.value:String
+  }
+}
+
+func testInitOverloading() {
+  let m1 = MultiInit() // $ type=m1:MultiInit target=MultiInit.init()
+  let m2 = MultiInit(int: 5) // $ type=m2:MultiInit target=MultiInit.init(int:)
+  let m3 = MultiInit(str: "x") // $ type=m3:MultiInit target=MultiInit.init(str:)
+  let m4 = MultiInit(x: 1, y: 2) // $ type=m4:MultiInit target=MultiInit.init(x:y:)
+  let v = m1.getValue() // $ type=v:String target=MultiInit.getValue
+}
+
+// --- Overload: static vs instance method ---
+
+class StaticVsInstance {
+  // StaticVsInstance.action()->instance
+  func action() -> String {
+    return "instance"
+  }
+
+  // StaticVsInstance.action()->static
+  static func action() -> String {
+    return "static"
+  }
+
+  // StaticVsInstance.init
+  init() {}
+}
+
+func testStaticVsInstance() {
+  let o = StaticVsInstance() // $ target=StaticVsInstance.init
+  let r1 = o.action() // $ type=r1:String target=StaticVsInstance.action()->instance
+  let r2 = StaticVsInstance.action() // $ type=r2:String target=StaticVsInstance.action()->static
+}
+
+// --- Overload: protocol extension default vs concrete implementation ---
+
+protocol Describable {
+  // Describable.describe
+  func describe() -> String
+}
+
+extension Describable {
+  // Describable.describe(default)
+  func describe() -> String {
+    return "default"
+  }
+
+  // Describable.extra
+  func extra() -> String {
+    return "extra"
+  }
+}
+
+class DescribableImpl : Describable {
+  // DescribableImpl.init
+  init() {}
+
+  // DescribableImpl.describe
+  func describe() -> String {
+    return "concrete"
+  }
+}
+
+func testProtocolExtensionOverload() {
+  let d = DescribableImpl() // $ target=DescribableImpl.init
+  let r1 = d.describe() // $ type=r1:String target=DescribableImpl.describe
+  let r2 = d.extra() // $ type=r2:String target=Describable.extra
+}
+
+// --- Overload: subclass override resolution ---
+
+class Base {
+  // Base.init
+  init() {}
+
+  // Base.action
+  func action() -> String {
+    return "base"
+  }
+
+  // Base.baseOnly
+  func baseOnly() -> String {
+    return "baseOnly"
+  }
+}
+
+class Sub : Base {
+  // Sub.init
+  override init() {
+    super.init() // $ target=Base.init
+  }
+
+  // Sub.action
+  override func action() -> String {
+    return "sub"
+  }
+
+  // Sub.subOnly
+  func subOnly() -> String {
+    return "subOnly"
+  }
+}
+
+class SubSub : Sub {
+  // SubSub.init
+  override init() {
+    super.init() // $ target=Sub.init
+  }
+
+  // SubSub.action
+  override func action() -> String {
+    return "subsub"
+  }
+}
+
+func testOverrideResolution() {
+  let b = Base() // $ target=Base.init
+  let rb = b.action() // $ type=rb:String target=Base.action
+
+  let s = Sub() // $ target=Sub.init
+  let rs = s.action() // $ type=rs:String target=Sub.action
+  let rbo = s.baseOnly() // $ type=rbo:String target=Base.baseOnly
+  let rso = s.subOnly() // $ type=rso:String target=Sub.subOnly
+
+  let ss = SubSub() // $ target=SubSub.init
+  let rss = ss.action() // $ type=rss:String target=SubSub.action
+  let rbo2 = ss.baseOnly() // $ type=rbo2:String target=Base.baseOnly
+  let rso2 = ss.subOnly() // $ type=rso2:String target=Sub.subOnly
+}
+
+// --- Overload: by external vs internal parameter names ---
+
+class LabelVariants {
+  // LabelVariants.send(to:)
+  func send(to target: String) -> String {
+    return target // $ type=target:String
+  }
+
+  // LabelVariants.send(from:)
+  func send(from source: String) -> String {
+    return source // $ type=source:String
+  }
+
+  // LabelVariants.send(to:from:)
+  func send(to target: String, from source: String) -> String {
+    return target + source
+  }
+}
+
+func testLabelVariants() {
+  let o = LabelVariants() // $ target=init()
+  let r1 = o.send(to: "x") // $ type=r1:String target=LabelVariants.send(to:)
+  let r2 = o.send(from: "y") // $ type=r2:String target=LabelVariants.send(from:)
+  let r3 = o.send(to: "x", from: "y") // $ type=r3:String target=LabelVariants.send(to:from:)
+}
+
+// --- Overload: generic function with different constraint satisfaction ---
+
+protocol Numeric2 : Equatable {
+  // Numeric2.zero
+  static func zero() -> Self
+}
+
+extension Int : Numeric2 {
+  // Int.zero
+  static func zero() -> Int { return 0 }
+}
+
+extension Double : Numeric2 {
+  // Double.zero
+  static func zero() -> Double { return 0.0 }
+}
+
+// constrainedId(_:Numeric2)
+func constrainedId<T: Numeric2>(_ x: T) -> T {
+  return x
+}
+
+// constrainedId(_:Equatable)
+func constrainedId<T: Equatable>(_ x: T) -> T {
+  return x
+}
+
+func testConstrainedOverload() {
+  let r1 = constrainedId(42) // $ type=r1:Int target=constrainedId(_:Numeric2)
+  let r2 = constrainedId("hello") // $ type=r2:String target=constrainedId(_:Equatable)
+}
+
+// --- Overload: methods on generic type specialized differently ---
+
+class Box<T> {
+  var item : T
+
+  // Box.init
+  init(_ item: T) {
+    self.item = item // $ type=item:T
+  }
+
+  // Box.get
+  func get() -> T {
+    return item // $ type=.item:T
+  }
+
+  // Box.replace
+  func replace(_ newItem: T) {
+    item = newItem // $ type=newItem:T
+  }
+}
+
+func testGenericMethodResolution() {
+  let intBox = Box(10) // $ type=intBox@Box<T>:Int target=Box.init
+  let strBox = Box("hi") // $ type=strBox@Box<T>:String target=Box.init
+  let v1 = intBox.get() // $ type=v1:Int target=Box.get
+  let v2 = strBox.get() // $ type=v2:String target=Box.get
+  intBox.replace(20) // $ target=Box.replace
+  strBox.replace("bye") // $ target=Box.replace
+}
+
+// --- Overload: convenience init vs designated init ---
+
+class Widget {
+  var name : String
+  var size : Int
+
+  // Widget.init(name:size:)
+  init(name: String, size: Int) {
+    self.name = name // $ type=name:String
+    self.size = size // $ type=size:Int
+  }
+
+  // Widget.init(name:)
+  convenience init(name: String) {
+    self.init(name: name, size: 1) // $ target=Widget.init(name:size:)
+  }
+
+  // Widget.init(size:)
+  convenience init(size: Int) {
+    self.init(name: "default", size: size) // $ target=Widget.init(name:size:)
+  }
+}
+
+func testConvenienceInit() {
+  let w1 = Widget(name: "a", size: 5) // $ type=w1:Widget target=Widget.init(name:size:)
+  let w2 = Widget(name: "b") // $ type=w2:Widget target=Widget.init(name:)
+  let w3 = Widget(size: 10) // $ type=w3:Widget target=Widget.init(size:)
+}
+
+// --- Overload: methods with closure parameters of different signatures ---
+
+class Processor {
+  // Processor.init
+  init() {}
+
+  // Processor.apply(_:(Int)->Int)
+  func apply(_ f: (Int) -> Int) -> Int {
+    return f(0)
+  }
+
+  // Processor.apply(_:(String)->String)
+  func apply(_ f: (String) -> String) -> String {
+    return f("")
+  }
+
+  // Processor.apply(_:(Int,Int)->Int)
+  func apply(_ f: (Int, Int) -> Int) -> Int {
+    return f(0, 0)
+  }
+}
+
+func testClosureOverload() {
+  let p = Processor() // $ target=Processor.init
+  let r1 = p.apply({ x in x + 1 }) // $ type=r1:Int target=Processor.apply(_:(Int)->Int)
+  let r2 = p.apply({ s in s + "!" }) // $ type=r2:String target=Processor.apply(_:(String)->String)
+  let r3 = p.apply({ x, y in x + y }) // $ type=r3:Int target=Processor.apply(_:(Int,Int)->Int)
+}
+
+// --- Overload: subscript-like method overloading ---
+
+class MultiSubscript {
+  var data : [Int] = [1, 2, 3]
+  var dict : [String: Int] = ["a": 1]
+
+  // MultiSubscript.init
+  init() {}
+
+  // MultiSubscript.get(_:)
+  func get(_ index: Int) -> Int {
+    return data[index]
+  }
+
+  // MultiSubscript.get(_:String)
+  func get(_ key: String) -> Int {
+    return dict[key] ?? 0
+  }
+}
+
+func testMethodSubscriptLike() {
+  let ms = MultiSubscript() // $ target=MultiSubscript.init
+  let r1 = ms.get(0) // $ type=r1:Int target=MultiSubscript.get(_:)
+  let r2 = ms.get("a") // $ type=r2:Int target=MultiSubscript.get(_:String)
+}

swift/ql/test/library-tests/type-inference/protocols.swift

@@ -0,0 +1,119 @@
+// --- Protocols and protocol conformance ---
+
+protocol Shape {
+  // Shape.area
+  func area() -> Double
+}
+
+struct Circle : Shape {
+  var radius : Double
+
+  // Circle.init
+  init(radius: Double) {
+    self.radius = radius // $ type=radius:Double
+  }
+
+  // Circle.area
+  func area() -> Double {
+    return 3.14159 * radius * radius // $ type=.radius:Double
+  }
+}
+
+struct Rectangle : Shape {
+  var width : Double
+  var height : Double
+
+  // Rectangle.init
+  init(width: Double, height: Double) {
+    self.width = width // $ type=width:Double
+    self.height = height // $ type=height:Double
+  }
+
+  // Rectangle.area
+  func area() -> Double {
+    return width * height // $ type=.width:Double
+  }
+}
+
+func testProtocol() {
+  let c = Circle(radius: 5.0) // $ type=c:Circle target=Circle.init
+  let a1 = c.area() // $ type=a1:Double target=Circle.area
+
+  let r = Rectangle(width: 3.0, height: 4.0) // $ type=r:Rectangle target=Rectangle.init
+  let a2 = r.area() // $ type=a2:Double target=Rectangle.area
+}
+
+// --- Protocol with associated types ---
+
+protocol Container {
+  associatedtype Item
+  // Container.getItem
+  func getItem() -> Item
+  // Container.count
+  func count() -> Int
+}
+
+struct IntContainer : Container {
+  typealias Item = Int
+  var items : [Int]
+
+  // IntContainer.init
+  init(items: [Int]) {
+    self.items = items
+  }
+
+  // IntContainer.getItem
+  func getItem() -> Int {
+    return items[0]
+  }
+
+  // IntContainer.count
+  func count() -> Int {
+    return items.count
+  }
+}
+
+func testAssociatedTypes() {
+  let ic = IntContainer(items: [1, 2, 3]) // $ type=ic:IntContainer target=IntContainer.init
+  let item = ic.getItem() // $ type=item:Int target=IntContainer.getItem
+  let cnt = ic.count() // $ type=cnt:Int target=IntContainer.count
+}
+
+// --- Multiple protocol conformance ---
+
+protocol Printable {
+  // Printable.display
+  func display() -> String
+}
+
+protocol Identifiable {
+  // Identifiable.id
+  func id() -> Int
+}
+
+class Entity : Printable, Identifiable {
+  var name : String
+  var entityId : Int
+
+  // Entity.init
+  init(name: String, entityId: Int) {
+    self.name = name // $ type=name:String
+    self.entityId = entityId // $ type=entityId:Int
+  }
+
+  // Entity.display
+  func display() -> String {
+    return name // $ type=.name:String
+  }
+
+  // Entity.id
+  func id() -> Int {
+    return entityId // $ type=.entityId:Int
+  }
+}
+
+func testMultipleProtocols() {
+  let e = Entity(name: "test", entityId: 42) // $ type=e:Entity target=Entity.init
+  let d = e.display() // $ type=d:String target=Entity.display
+  let eid = e.id() // $ type=eid:Int target=Entity.id
+}

swift/ql/test/library-tests/type-inference/type-inference.ql

@@ -0,0 +1,89 @@
+import swift
+import TestUtils
+import utils.test.InlineExpectationsTest
+
+pragma[nomagic]
+private predicate declHasPotentialCommentAt(Decl d, string path, int line) {
+  d.getLocation().hasLocationInfo(path, line + 1, _, _, _)
+}
+
+pragma[nomagic]
+private SingleLineComment getPrecedingComment(Decl d) {
+  exists(string path, int line |
+    declHasPotentialCommentAt(d, path, line) and
+    result.getLocation().hasLocationInfo(path, line, _, _, _)
+  )
+}
+
+module ResolveTest implements TestSig {
+  string getARelevantTag() { result = "target" }
+
+  private predicate declHasName(Decl c, string value) {
+    exists(string s |
+      s = getPrecedingComment(c).getText() and
+      value = s.substring(3, s.length() - 1)
+    )
+    or
+    not exists(getPrecedingComment(c)) and
+    value = [c.(EnumElementDecl).getName(), c.(Function).getName()]
+  }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(AstNode source, Decl target |
+      location = source.getLocation() and
+      element = source.toString() and
+      target =
+        [
+          source.(CallExpr).getStaticTarget().(Decl), source.(MethodLookupExpr).getMember(),
+          source.(EnumElementPattern).getElement()
+        ] and
+      declHasName(target, value) and
+      tag = "target" and
+      toBeTested(source) and
+      toBeTested(target)
+    )
+  }
+}
+
+private Type getTypeAt(Type t, string path) {
+  path = "" and
+  result = t.getUnderlyingType()
+  or
+  exists(BoundGenericType b, GenericTypeDecl decl |
+    b = t and
+    decl = b.getDeclaration()
+  |
+    exists(string prefix, string suffix, int i |
+      result = getTypeAt(b.getArgType(i).getUnderlyingType(), suffix) and
+      prefix = decl.getName() + "<" + decl.getGenericTypeParam(i).getName() + ">" and
+      if suffix = "" then path = prefix else path = prefix + "." + suffix
+    )
+  )
+}
+
+module TypeTest implements TestSig {
+  string getARelevantTag() { result = "type" }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) { none() }
+
+  predicate hasOptionalResult(Location location, string element, string tag, string value) {
+    exists(Locatable e, string path, Type t, Type t0 |
+      t = [e.(Expr).getType(), e.(VarDecl).getType()] and
+      tag = "type" and
+      location = e.getLocation() and
+      t0 = getTypeAt(t, path) and
+      exists(string name, string at |
+        name = t0.(AnyGenericType).getDeclaration().getName()
+        or
+        not t0 instanceof AnyGenericType and
+        name = t0.getName()
+      |
+        (if path = "" then at = "" else at = "@" + path) and
+        value = element + at + ":" + name and
+        element = e.toString()
+      )
+    )
+  }
+}
+
+import MakeTest<MergeTests<ResolveTest, TypeTest>>

swift/ql/test/library-tests/type-inference/type_constraints.swift

@@ -0,0 +1,300 @@
+// --- where clause on generic function ---
+
+// minOf(_:_:)
+func minOf<T: Comparable>(_ a: T, _ b: T) -> T {
+  if a < b { return a } else { return b }
+}
+
+// maxOf(_:_:)
+func maxOf<T>(_ a: T, _ b: T) -> T where T : Comparable {
+  if a > b { return a } else { return b }
+}
+
+func testWhereClause() {
+  let m1 = minOf(3, 7) // $ type=m1:Int target=minOf(_:_:)
+  let m2 = minOf("a", "z") // $ type=m2:String target=minOf(_:_:)
+  let m3 = maxOf(3, 7) // $ type=m3:Int target=maxOf(_:_:)
+  let m4 = maxOf("a", "z") // $ type=m4:String target=maxOf(_:_:)
+}
+
+// --- Multiple constraints on a single type parameter ---
+
+protocol Displayable2 {
+  // Displayable2.display
+  func display() -> String
+}
+
+protocol Sortable {
+  // Sortable.sortKey
+  func sortKey() -> Int
+}
+
+struct TaggedItem : Displayable2, Sortable, Equatable {
+  var tag : String
+  var priority : Int
+
+  // TaggedItem.init
+  init(tag: String, priority: Int) {
+    self.tag = tag // $ type=tag:String
+    self.priority = priority // $ type=priority:Int
+  }
+
+  // TaggedItem.display
+  func display() -> String {
+    return tag // $ type=.tag:String
+  }
+
+  // TaggedItem.sortKey
+  func sortKey() -> Int {
+    return priority // $ type=.priority:Int
+  }
+}
+
+// showAndSort(_:)
+func showAndSort<T: Displayable2 & Sortable>(_ item: T) -> String {
+  return item.display() // $ target=Displayable2.display
+}
+
+// showSortAndCompare(_:_:)
+func showSortAndCompare<T>(_ a: T, _ b: T) -> Bool where T : Displayable2, T : Sortable, T : Equatable {
+  return a == b
+}
+
+func testMultipleConstraints() {
+  let item = TaggedItem(tag: "x", priority: 1) // $ target=TaggedItem.init
+  let s = showAndSort(item) // $ type=s:String target=showAndSort(_:)
+  let eq = showSortAndCompare(item, item) // $ type=eq:Bool target=showSortAndCompare(_:_:)
+}
+
+// --- Generic class with multiple constrained type parameters ---
+
+class SortedPair<T: Comparable, U: Comparable> {
+  var first : T
+  var second : U
+
+  // SortedPair.init
+  init(first: T, second: U) {
+    self.first = first // $ type=first:T
+    self.second = second // $ type=second:U
+  }
+
+  // SortedPair.isFirstSmaller
+  func isFirstSmaller(than other: T) -> Bool {
+    return first < other // $ type=other:T
+  }
+
+  // SortedPair.isSecondSmaller
+  func isSecondSmaller(than other: U) -> Bool {
+    return second < other // $ type=other:U
+  }
+}
+
+func testMultiConstrainedParams() {
+  let sp = SortedPair(first: 3, second: "b") // $ target=SortedPair.init
+  let r1 = sp.isFirstSmaller(than: 5) // $ type=r1:Bool target=SortedPair.isFirstSmaller
+  let r2 = sp.isSecondSmaller(than: "z") // $ type=r2:Bool target=SortedPair.isSecondSmaller
+}
+
+// --- Associated type constraints (same-type constraint) ---
+
+protocol ElementContainer {
+  associatedtype Element
+  // ElementContainer.first
+  func first() -> Element
+}
+
+struct IntArray : ElementContainer {
+  typealias Element = Int
+  var items : [Int]
+
+  // IntArray.init
+  init(items: [Int]) {
+    self.items = items
+  }
+
+  // IntArray.first
+  func first() -> Int {
+    return items[0]
+  }
+}
+
+struct StringArray : ElementContainer {
+  typealias Element = String
+  var items : [String]
+
+  // StringArray.init
+  init(items: [String]) {
+    self.items = items
+  }
+
+  // StringArray.first
+  func first() -> String {
+    return items[0]
+  }
+}
+
+// extractFirst(from:Int)
+func extractFirst<C: ElementContainer>(from container: C) -> C.Element where C.Element == Int {
+  return container.first() // $ target=ElementContainer.first
+}
+
+// extractFirst(from:String)
+func extractFirst<C: ElementContainer>(from container: C) -> C.Element where C.Element == String {
+  return container.first() // $ target=ElementContainer.first
+}
+
+func testSameTypeConstraint() {
+  let ia = IntArray(items: [10, 20]) // $ target=IntArray.init
+  let sa = StringArray(items: ["hi", "there"]) // $ target=StringArray.init
+  let r1 = extractFirst(from: ia) // $ type=r1:Int target=extractFirst(from:Int)
+  let r2 = extractFirst(from: sa) // $ type=r2:String target=extractFirst(from:String)
+}
+
+// --- Superclass constraint on type parameter ---
+
+class Vehicle {
+  var speed : Int
+
+  // Vehicle.init
+  init(speed: Int) {
+    self.speed = speed // $ type=speed:Int
+  }
+
+  // Vehicle.describe
+  func describe() -> String {
+    return "vehicle"
+  }
+}
+
+class Car : Vehicle {
+  // Car.init
+  override init(speed: Int) {
+    super.init(speed: speed) // $ target=Vehicle.init
+  }
+
+  // Car.describe
+  override func describe() -> String {
+    return "car"
+  }
+
+  // Car.honk
+  func honk() -> String {
+    return "beep"
+  }
+}
+
+class Truck : Vehicle {
+  // Truck.init
+  override init(speed: Int) {
+    super.init(speed: speed) // $ target=Vehicle.init
+  }
+
+  // Truck.describe
+  override func describe() -> String {
+    return "truck"
+  }
+
+  // Truck.haul
+  func haul() -> String {
+    return "hauling"
+  }
+}
+
+// describeVehicle(_:)
+func describeVehicle<T: Vehicle>(_ v: T) -> String {
+  return v.describe() // $ target=Vehicle.describe
+}
+
+func testSuperclassConstraint() {
+  let car = Car(speed: 100) // $ type=car:Car target=Car.init
+  let truck = Truck(speed: 60) // $ type=truck:Truck target=Truck.init
+  let d1 = describeVehicle(car) // $ type=d1:String target=describeVehicle(_:)
+  let d2 = describeVehicle(truck) // $ type=d2:String target=describeVehicle(_:)
+  let h = car.honk() // $ type=h:String target=Car.honk
+  let hl = truck.haul() // $ type=hl:String target=Truck.haul
+}
+
+// --- Constrained extension methods ---
+
+protocol Summable {
+  // Summable.+
+  static func +(lhs: Self, rhs: Self) -> Self
+}
+
+extension Int : Summable {}
+extension Double : Summable {}
+extension String : Summable {}
+
+struct Accumulator<T> {
+  var values : [T]
+
+  // Accumulator.init
+  init(values: [T]) {
+    self.values = values
+  }
+
+  // Accumulator.count
+  func count() -> Int {
+    return values.count
+  }
+}
+
+extension Accumulator where T : Summable {
+  // Accumulator.total
+  func total() -> T {
+    return values[0] + values[1] // $ target=Summable.+
+  }
+}
+
+extension Accumulator where T : Equatable {
+  // Accumulator.contains
+  func contains(_ item: T) -> Bool {
+    return values.contains(where: { $0 == item })
+  }
+}
+
+func testConstrainedExtensions() {
+  let intAcc = Accumulator(values: [1, 2, 3]) // $ target=Accumulator.init
+  let cnt = intAcc.count() // $ type=cnt:Int target=Accumulator.count
+  let tot = intAcc.total() // $ type=tot:Int target=Accumulator.total
+  let has = intAcc.contains(2) // $ type=has:Bool target=Accumulator.contains
+}
+
+// --- Generic method with its own constrained type parameter ---
+
+class Transformer {
+  // Transformer.init
+  init() {}
+
+  // Transformer.transform
+  func transform<T: Summable>(_ items: [T]) -> T {
+    return items[0] + items[1] // $ target=Summable.+
+  }
+
+  // Transformer.merge
+  func merge<A: Equatable, B: Equatable>(_ a: A, _ b: B) -> Bool {
+    return true
+  }
+}
+
+func testMethodTypeParams() {
+  let t = Transformer() // $ target=Transformer.init
+  let r1 = t.transform([3, 1, 2]) // $ type=r1:Int target=Transformer.transform
+  let r2 = t.transform(["c", "a", "b"]) // $ type=r2:String target=Transformer.transform
+  let r3 = t.merge(1, "x") // $ type=r3:Bool target=Transformer.merge
+}
+
+// --- Recursive constraint (Comparable requiring Equatable) ---
+
+// clamp(_:min:max:)
+func clamp<T: Comparable>(_ value: T, min lower: T, max upper: T) -> T {
+  if value < lower { return lower }
+  if value > upper { return upper }
+  return value
+}
+
+func testRecursiveConstraint() {
+  let r1 = clamp(5, min: 0, max: 10) // $ type=r1:Int target=clamp(_:min:max:)
+  let r2 = clamp(3.5, min: 1.0, max: 2.0) // $ type=r2:Double target=clamp(_:min:max:)
+  let r3 = clamp("m", min: "a", max: "z") // $ type=r3:String target=clamp(_:min:max:)
+}