Allow using non-escapable types as suites.

This PR enables using non-escapable types as suites. For example:

```swift
@suite struct NumberOfBeesTests: ~Escapable {
  @test borrowing func countBees() { ... }
}
```

Non-escapable types have a number of constraints in Swift, and those constraints
aren't lifted in a test target, but generally speaking a non-escapable type
should be able to do all the things any other type can do _as a test suite_.

Author: grynspan

Package.swift

@@ -171,6 +171,7 @@ extension Array where Element == PackageDescription.SwiftSetting {
       .unsafeFlags(["-require-explicit-sendable"]),
       .enableUpcomingFeature("ExistentialAny"),
       .enableExperimentalFeature("SuppressedAssociatedTypes"),
+      .enableExperimentalFeature("LifetimeDependence"),
 
       .enableExperimentalFeature("AccessLevelOnImport"),
       .enableUpcomingFeature("InternalImportsByDefault"),

Sources/Testing/Parameterization/TypeInfo.swift

@@ -18,7 +18,7 @@ public struct TypeInfo: Sendable {
     ///
     /// - Parameters:
     ///   - type: The concrete metatype.
-    case type(_ type: any ~Copyable.Type)
+    case type(_ type: any (~Copyable & ~Escapable).Type)
 
     /// The type info represents a metatype, but a reference to that metatype is
     /// not available at runtime.
@@ -38,7 +38,7 @@ public struct TypeInfo: Sendable {
   ///
   /// If this instance was created from a type name, or if it was previously
   /// encoded and decoded, the value of this property is `nil`.
-  public var type: (any ~Copyable.Type)? {
+  public var type: (any (~Copyable & ~Escapable).Type)? {
     if case let .type(type) = _kind {
       return type
     }
@@ -79,7 +79,7 @@ public struct TypeInfo: Sendable {
   ///
   /// - Parameters:
   ///   - type: The type which this instance should describe.
-  init(describing type: any ~Copyable.Type) {
+  init(describing type: any (~Copyable & ~Escapable).Type) {
     _kind = .type(type)
   }
 
@@ -265,11 +265,9 @@ extension TypeInfo {
     }
     switch _kind {
     case let .type(type):
-#if compiler(>=6.1)
-      return _mangledTypeName(type)
-#else
+      // _mangledTypeName() works with non-escaping types, but its signature has
+      // not been updated yet. SEE: rdar://145945680
       return _mangledTypeName(unsafeBitCast(type, to: Any.Type.self))
-#endif
     case let .nameOnly(_, _, mangledName):
       return mangledName
     }
@@ -379,7 +377,7 @@ extension ObjectIdentifier {
   ///
   /// - Bug: The standard library should support this conversion.
   ///   ([134276458](rdar://134276458), [134415960](rdar://134415960))
-  fileprivate init(_ type: any ~Copyable.Type) {
+  fileprivate init(_ type: any (~Copyable & ~Escapable).Type) {
     self.init(unsafeBitCast(type, to: Any.Type.self))
   }
 }

Sources/Testing/Test+Macro.swift

@@ -53,9 +53,8 @@ public typealias __XCTestCompatibleSelector = Never
 /// - Parameters:
 ///   - traits: Zero or more traits to apply to this test suite.
 ///
-/// A test suite is a type that contains one or more test functions. Any
-/// copyable type (that is, any type that is not marked `~Copyable`) may be a
-/// test suite.
+/// A test suite is a type that contains one or more test functions. Any type
+/// may be a test suite.
 ///
 /// The use of the `@Suite` attribute is optional; types are recognized as test
 /// suites even if they do not have the `@Suite` attribute applied to them.
@@ -81,9 +80,8 @@ public macro Suite(
 ///     from the associated type's name.
 ///   - traits: Zero or more traits to apply to this test suite.
 ///
-/// A test suite is a type that contains one or more test functions. Any
-/// copyable type (that is, any type that is not marked `~Copyable`) may be a
-/// test suite.
+/// A test suite is a type that contains one or more test functions. Any type
+/// may be a test suite.
 ///
 /// The use of the `@Suite` attribute is optional; types are recognized as test
 /// suites even if they do not have the `@Suite` attribute applied to them.
@@ -106,7 +104,7 @@ extension Test {
   /// - Warning: This function is used to implement the `@Suite` macro. Do not
   ///   call it directly.
   public static func __type(
-    _ containingType: any ~Copyable.Type,
+    _ containingType: any (~Copyable & ~Escapable).Type,
     displayName: String? = nil,
     traits: [any SuiteTrait],
     sourceLocation: SourceLocation
@@ -159,7 +157,7 @@ extension Test {
   ///   call it directly.
   public static func __function(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: (any (~Copyable & ~Escapable).Type)?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
@@ -241,7 +239,7 @@ extension Test {
   ///   call it directly.
   public static func __function<C>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: (any (~Copyable & ~Escapable).Type)?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
@@ -376,7 +374,7 @@ extension Test {
   ///   call it directly.
   public static func __function<C1, C2>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: (any (~Copyable & ~Escapable).Type)?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
@@ -404,7 +402,7 @@ extension Test {
   ///   call it directly.
   public static func __function<C, E1, E2>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: (any (~Copyable & ~Escapable).Type)?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
@@ -435,7 +433,7 @@ extension Test {
   ///   call it directly.
   public static func __function<Key, Value>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: (any (~Copyable & ~Escapable).Type)?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
@@ -460,7 +458,7 @@ extension Test {
   ///   call it directly.
   public static func __function<C1, C2>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: (any (~Copyable & ~Escapable).Type)?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
@@ -524,7 +522,7 @@ extension Test {
 ///
 /// - Warning: This function is used to implement the `@Test` macro. Do not use
 ///   it directly.
-@inlinable public func __requiringTry<T>(_ value: consuming T) throws -> T where T: ~Copyable {
+@inlinable public func __requiringTry<T>(_ value: consuming T) throws -> T where T: ~Copyable & ~Escapable {
   value
 }
 
@@ -533,7 +531,7 @@ extension Test {
 ///
 /// - Warning: This function is used to implement the `@Test` macro. Do not use
 ///   it directly.
-@inlinable public func __requiringAwait<T>(_ value: consuming T, isolation: isolated (any Actor)? = #isolation) async -> T where T: ~Copyable {
+@inlinable public func __requiringAwait<T>(_ value: consuming T, isolation: isolated (any Actor)? = #isolation) async -> T where T: ~Copyable & ~Escapable {
   value
 }
 
@@ -556,7 +554,7 @@ public var __defaultSynchronousIsolationContext: (any Actor)? {
   _ selector: __XCTestCompatibleSelector?,
   onInstanceOf type: T.Type,
   sourceLocation: SourceLocation
-) async throws -> Bool where T: ~Copyable {
+) async throws -> Bool where T: ~Copyable & ~Escapable {
   false
 }
 

Tests/TestingTests/CustomTestStringConvertibleTests.swift

@@ -54,7 +54,7 @@ struct CustomTestStringConvertibleTests {
 
 // MARK: - Fixtures
 
-private struct NonCopyableType: ~Copyable {}
+private struct NonCopyableType: ~Copyable, ~Escapable {}
 
 private struct CustomStringConvertibleType: CustomStringConvertible {
   var description: String {

Tests/TestingTests/NonCopyableSuiteTests.swift

@@ -11,7 +11,7 @@
 @testable @_spi(ForToolsIntegrationOnly) import Testing
 
 @Suite("Non-Copyable Tests")
-struct NonCopyableTests: ~Copyable {
+struct NonCopyableTests: ~Copyable, ~Escapable {
   @Test static func staticMe() {}
   @Test borrowing func borrowMe() {}
   @Test consuming func consumeMe() {}

cmake/modules/shared/CompilerSettings.cmake

@@ -14,7 +14,8 @@ add_compile_options(
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -require-explicit-sendable>")
 add_compile_options(
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend AccessLevelOnImport>"
-  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend SuppressedAssociatedTypes>")
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend SuppressedAssociatedTypes>"
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend LifetimeDependence>")
 add_compile_options(
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-upcoming-feature -Xfrontend ExistentialAny>"
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-upcoming-feature -Xfrontend InternalImportsByDefault>")