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When a generic function has potentially Escapable outputs, those outputs declare lifetime dependencies, which have no effect when substitution leads to those types becoming `Escapable` in a concrete context. This means that type substitution should canonically eliminate lifetime dependencies targeting Escapable parameters or returns, and that type checking should allow a function value with potentially-Escapable lifetime dependencies to bind to a function type without those dependencies when the target of the dependencies is Escapable. Fixes rdar://147533059.
53 lines
1.6 KiB
Swift
53 lines
1.6 KiB
Swift
// RUN: %target-swift-frontend -enable-experimental-feature LifetimeDependence -emit-sil -verify %s
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// REQUIRES: swift_feature_LifetimeDependence
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@lifetime(copy x)
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func id<T: ~Escapable>(_ x: T) -> T {
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return x
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}
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func double<T>(_ f: @escaping (T) -> T) -> (T) -> T {
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return { f(f($0)) }
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}
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func doubleid() -> (Int) -> Int {
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// Substituting `id` with `T = Int` renders its return type Escapable,
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// eliminating the lifetime dependency and allowing the function to be
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// used as a `(T) -> T` value.
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return double(id)
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}
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func doubleidGeneric<U>(_: U.Type) -> (U) -> U {
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// Substituting `id` with `T = U` renders its return type Escapable,
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// eliminating the lifetime dependency and allowing the function to be
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// used as a `(T) -> T` value.
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return double(id)
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}
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@lifetime(x: copy y)
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func overwrite<T: ~Escapable>(_ x: inout T, _ y: T) {
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x = y
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}
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func doubleInout<T>(_ f: @escaping (inout T, T) -> Void) -> (inout T, T) -> Void {
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return {
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f(&$0, $1)
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f(&$0, $1)
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}
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}
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func doubleOverwrite() -> (inout Int, Int) -> Void {
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// Substituting `id` with `T = Int` renders the `inout` parameter Escapable,
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// eliminating the lifetime dependency and allowing the function to be
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// used as a `(inout T, T) -> T` value.
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return doubleInout(overwrite)
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}
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func doubleOverwriteGeneric<U>(_: U.Type) -> (inout U, U) -> Void {
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// Substituting `id` with `T = U` renders the `inout` parameter Escapable,
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// eliminating the lifetime dependency and allowing the function to be
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// used as a `(inout T, T) -> T` value.
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return doubleInout(overwrite)
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}
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