Allow non-escapable types as suites. (#1468)

This PR enables `@Suite` on non-escapable types and `@Test` on functions
within them. We need to use the experimental `@_lifetime` attribute on
some helper functions to ensure this works. Developers who want to write
tests on `~Escapable` types will also need to enable the experimental
"Lifetimes" feature.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: grynspan

Package.swift

@@ -384,6 +384,9 @@ extension Array where Element == PackageDescription.SwiftSetting {
       // proposal via Swift Evolution.
       .enableExperimentalFeature("SymbolLinkageMarkers"),
 
+      // Enabled to allow tests to be added to ~Escapable suites.
+      .enableExperimentalFeature("Lifetimes"),
+
       .enableUpcomingFeature("InferIsolatedConformances"),
 
       // When building as a package, the macro plugin always builds as an

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: (some ~Copyable).Type) {
+  init<T>(describing type: T.Type) where T: ~Copyable & ~Escapable {
     _kind = .type(type)
   }
 
@@ -101,7 +101,7 @@ public struct TypeInfo: Sendable {
   ///
   /// - Parameters:
   ///   - value: The value whose type this instance should describe.
-  init<T>(describingTypeOf value: borrowing T) where T: ~Copyable {
+  init<T>(describingTypeOf value: borrowing T) where T: ~Copyable & ~Escapable {
     self.init(describing: T.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
-/// escapable type (that is, any type that is not marked `~Escapable`) 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
-/// escapable type (that is, any type that is not marked `~Escapable`) 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.
@@ -105,12 +103,12 @@ 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,
+  public static func __type<S>(
+    _ containingType: S.Type,
     displayName: String? = nil,
     traits: [any SuiteTrait],
     sourceLocation: SourceLocation
-  ) -> Self {
+  ) -> Self where S: ~Copyable & ~Escapable {
     let containingTypeInfo = TypeInfo(describing: containingType)
     return Self(displayName: displayName, traits: traits, sourceLocation: sourceLocation, containingTypeInfo: containingTypeInfo)
   }
@@ -166,7 +164,7 @@ extension Test {
     sourceLocation: SourceLocation,
     parameters: [__Parameter] = [],
     testFunction: @escaping @Sendable () async throws -> Void
-  ) -> Self where S: ~Copyable {
+  ) -> Self where S: ~Copyable & ~Escapable {
     // Don't use Optional.map here due to a miscompile/crash. Expand out to an
     // if expression instead. SEE: rdar://134280902
     let containingTypeInfo: TypeInfo? = if let containingType {
@@ -251,7 +249,7 @@ extension Test {
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable (C.Element) async throws -> Void
-  ) -> Self where S: ~Copyable, C: Collection & Sendable, C.Element: Sendable {
+  ) -> Self where S: ~Copyable & ~Escapable, C: Collection & Sendable, C.Element: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -398,7 +396,7 @@ extension Test {
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable (C1.Element, C2.Element) async throws -> Void
-  ) -> Self where S: ~Copyable, C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
+  ) -> Self where S: ~Copyable & ~Escapable, C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -426,7 +424,7 @@ extension Test {
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable ((E1, E2)) async throws -> Void
-  ) -> Self where S: ~Copyable, C: Collection & Sendable, C.Element == (E1, E2), E1: Sendable, E2: Sendable {
+  ) -> Self where S: ~Copyable & ~Escapable, C: Collection & Sendable, C.Element == (E1, E2), E1: Sendable, E2: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -457,7 +455,7 @@ extension Test {
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable ((Key, Value)) async throws -> Void
-  ) -> Self where S: ~Copyable, Key: Sendable, Value: Sendable {
+  ) -> Self where S: ~Copyable & ~Escapable, Key: Sendable, Value: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -482,7 +480,7 @@ extension Test {
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable (C1.Element, C2.Element) async throws -> Void
-  ) -> Self where S: ~Copyable, C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
+  ) -> Self where S: ~Copyable & ~Escapable, C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -538,7 +536,8 @@ 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 {
+@_lifetime(copy value)
+@inlinable public func __requiringTry<T>(_ value: consuming T) throws -> T where T: ~Copyable & ~Escapable {
   value
 }
 
@@ -547,7 +546,8 @@ 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 {
+@_lifetime(copy value)
+@inlinable public func __requiringAwait<T>(_ value: consuming T, isolation: isolated (any Actor)? = #isolation) async -> T where T: ~Copyable & ~Escapable {
   value
 }
 
@@ -556,7 +556,8 @@ extension Test {
 ///
 /// - Warning: This function is used to implement the `@Test` macro. Do not use
 ///   it directly.
-@unsafe @inlinable public func __requiringUnsafe<T>(_ value: consuming T) -> T where T: ~Copyable {
+@_lifetime(copy value)
+@unsafe @inlinable public func __requiringUnsafe<T>(_ value: consuming T) -> T where T: ~Copyable & ~Escapable {
   value
 }
 
@@ -579,7 +580,7 @@ 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
 }
 

Sources/TestingMacros/Support/DiagnosticMessage.swift

@@ -327,19 +327,14 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
   ///     generic.
   ///   - attribute: The `@Test` or `@Suite` attribute.
   ///   - decl: The declaration in question (contained in `node`.)
-  ///   - escapableNonConformance: The suppressed conformance to `Escapable` for
-  ///     `decl`, if present.
   ///
   /// - Returns: A diagnostic message.
-  static func containingNodeUnsupported(_ node: some SyntaxProtocol, genericBecauseOf genericClause: Syntax? = nil, whenUsing attribute: AttributeSyntax, on decl: some SyntaxProtocol, withSuppressedConformanceToEscapable escapableNonConformance: SuppressedTypeSyntax? = nil) -> Self {
+  static func containingNodeUnsupported(_ node: some SyntaxProtocol, genericBecauseOf genericClause: Syntax? = nil, whenUsing attribute: AttributeSyntax, on decl: some SyntaxProtocol) -> Self {
     // Avoid using a syntax node from a lexical context (it won't have source
     // location information.)
     let syntax: Syntax = if let genericClause, attribute.root == genericClause.root {
       // Prefer the generic clause if available as the root cause.
       genericClause
-    } else if let escapableNonConformance, attribute.root == escapableNonConformance.root {
-      // Then the ~Escapable conformance if present.
-      Syntax(escapableNonConformance)
     } else if attribute.root == node.root {
       // Next best choice is the unsupported containing node.
       Syntax(node)
@@ -373,9 +368,7 @@ struct DiagnosticMessage: SwiftDiagnostics.DiagnosticMessage {
         message += " within \(_kindString(for: node, includeA: true))"
       }
     }
-    if escapableNonConformance != nil {
-      message += " because its conformance to 'Escapable' has been suppressed"
-    } else if let decl = node.as(DeclSyntax.self), declarationInheritsFromXCTestClass(decl) == true {
+    if let decl = node.as(DeclSyntax.self), declarationInheritsFromXCTestClass(decl) == true {
       message += " because it is a subclass of 'XCTest', 'XCTestCase', or 'XCTestSuite'"
     }
 

Sources/TestingMacros/TestDeclarationMacro.swift

@@ -134,21 +134,6 @@ public struct TestDeclarationMacro: PeerMacro, Sendable {
       }
     }
 
-    // Disallow non-escapable types as suites. In order to support them, the
-    // compiler team needs to finish implementing the lifetime dependency
-    // feature so that `init()`, ``__requiringTry()`, and `__requiringAwait()`
-    // can be correctly expressed.
-    if let containingType = lexicalContext.first?.asProtocol((any DeclGroupSyntax).self),
-       let inheritedTypes = containingType.inheritanceClause?.inheritedTypes {
-      let escapableNonConformances = inheritedTypes
-        .map(\.type)
-        .compactMap { $0.as(SuppressedTypeSyntax.self) }
-        .filter { $0.type.isNamed("Escapable", inModuleNamed: "Swift") }
-      for escapableNonConformance in escapableNonConformances {
-        diagnostics.append(.containingNodeUnsupported(containingType, whenUsing: testAttribute, on: function, withSuppressedConformanceToEscapable: escapableNonConformance))
-      }
-    }
-
     return !diagnostics.lazy.map(\.severity).contains(.error)
   }
 

Tests/TestingMacrosTests/TestDeclarationMacroTests.swift

@@ -159,12 +159,6 @@ struct TestDeclarationMacroTests {
         "Attribute 'Test' cannot be applied to a function within a generic extension to type 'T!'",
       "extension T! { @Suite struct S {} }":
         "Attribute 'Suite' cannot be applied to a structure within a generic extension to type 'T!'",
-      "struct S: ~Escapable { @Test func f() {} }":
-        "Attribute 'Test' cannot be applied to a function within structure 'S' because its conformance to 'Escapable' has been suppressed",
-      "struct S: ~Swift.Escapable { @Test func f() {} }":
-        "Attribute 'Test' cannot be applied to a function within structure 'S' because its conformance to 'Escapable' has been suppressed",
-      "struct S: ~(Escapable) { @Test func f() {} }":
-        "Attribute 'Test' cannot be applied to a function within structure 'S' because its conformance to 'Escapable' has been suppressed",
     ]
   )
   func apiMisuseErrors(input: String, expectedMessage: String) throws {

Tests/TestingTests/NonCopyableSuiteTests.swift

@@ -10,8 +10,8 @@
 
 @testable @_spi(ForToolsIntegrationOnly) import Testing
 
-@Suite("Non-Copyable Tests")
-struct NonCopyableTests: ~Copyable {
+@Suite("Non-Copyable/Non-Escapable Tests")
+struct NonCopyableTests: ~Copyable & ~Escapable {
   @Test static func staticMe() {}
   @Test borrowing func borrowMe() {}
   @Test consuming func consumeMe() {}

cmake/modules/shared/CompilerSettings.cmake

@@ -15,7 +15,8 @@ add_compile_options(
 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 AccessLevelOnImport>"
+  "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-experimental-feature -Xfrontend Lifetimes>")
 add_compile_options(
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-upcoming-feature -Xfrontend ExistentialAny>"
   "SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xfrontend -enable-upcoming-feature -Xfrontend InternalImportsByDefault>"