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f44064cbbc
Introduce callables: values of types that declare `func callAsFunction`
methods can be called like functions. The call syntax is shorthand for
applying `func callAsFunction` methods.
```swift
struct Adder {
var base: Int
func callAsFunction(_ x: Int) -> Int {
return x + base
}
}
var adder = Adder(base: 3)
adder(10) // desugars to `adder.callAsFunction(10)`
```
`func callAsFunction` argument labels are required at call sites.
Multiple `func callAsFunction` methods on a single type are supported.
`mutating func callAsFunction` is supported.
SR-11378 tracks improving `callAsFunction` diagnostics.
62 lines
1.3 KiB
Swift
62 lines
1.3 KiB
Swift
// RUN: %target-typecheck-verify-swift
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protocol P0 {
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// expected-note @+1 {{protocol requires function 'callAsFunction()' with type '() -> Missing'; do you want to add a stub?}}
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func callAsFunction() -> Self
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}
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func testProtocol(_ x: P0) {
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_ = x()
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}
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func testGeneric<T : P0>(_ x: T) {
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_ = x()
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}
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protocol P1 {
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func callAsFunction() -> Self
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}
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extension P1 {
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// expected-note @+1 {{found this candidate}}
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func callAsFunction() -> Self {
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return self
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}
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}
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protocol P2 {}
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extension P2 {
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// expected-note @+1 {{found this candidate}}
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func callAsFunction(x: Int, y: Int) -> Int {
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return x + y
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}
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}
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// expected-error @+1 {{type 'Missing' does not conform to protocol 'P0'}}
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struct Missing : P0 {}
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struct S0 : P0 {
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@discardableResult
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func callAsFunction() -> S0 { return self }
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}
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let s0 = S0()
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s0()
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struct S1 : P1 {
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func callAsFunction() -> S1 { return self }
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}
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let s1 = S1()
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_ = s1()()
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struct Conforming : P0 & P1 & P2 {}
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let conforming = Conforming()
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_ = conforming(x: 1, y: 2)
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_ = conforming().callAsFunction(x:y:)(1, 2)
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_ = conforming.callAsFunction(x:y:)
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_ = conforming.callAsFunction // expected-error {{ambiguous use of 'callAsFunction'}}
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protocol P3 {}
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extension P3 {
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func callAsFunction() -> Self { return self }
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}
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struct S3 : P3 {}
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let s3 = S3()
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_ = s3()()
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