Use generics to declare suite types in macro expansions. (#1338)

This PR adopts generics instead of existentials when declaring suite
types in the expansions of `@Suite` and `@Test` and in the interface of
the internal `TypeInfo` helper type.

### 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

Sources/Testing/Parameterization/TypeInfo.swift

@@ -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: (some ~Copyable).Type) {
     _kind = .type(type)
   }
 
@@ -88,8 +88,21 @@ public struct TypeInfo: Sendable {
   ///
   /// - Parameters:
   ///   - value: The value whose type this instance should describe.
-  init(describingTypeOf value: Any) {
-    self.init(describing: Swift.type(of: value))
+  init(describingTypeOf value: some Any) {
+#if !hasFeature(Embedded)
+    let value = value as Any
+#endif
+    let type = Swift.type(of: value)
+    self.init(describing: type)
+  }
+
+  /// Initialize an instance of this type describing the type of the specified
+  /// value.
+  ///
+  /// - Parameters:
+  ///   - value: The value whose type this instance should describe.
+  init<T>(describingTypeOf value: borrowing T) where T: ~Copyable {
+    self.init(describing: T.self)
   }
 }
 

Sources/Testing/Test+Macro.swift

@@ -157,16 +157,16 @@ extension Test {
   ///
   /// - Warning: This function is used to implement the `@Test` macro. Do not
   ///   call it directly.
-  public static func __function(
+  public static func __function<S>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: S.Type?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
     sourceLocation: SourceLocation,
     parameters: [__Parameter] = [],
     testFunction: @escaping @Sendable () async throws -> Void
-  ) -> Self {
+  ) -> Self where S: ~Copyable {
     // 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 {
@@ -241,17 +241,17 @@ extension Test {
   ///
   /// - Warning: This function is used to implement the `@Test` macro. Do not
   ///   call it directly.
-  public static func __function<C>(
+  public static func __function<S, C>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: S.Type?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
     arguments collection: @escaping @Sendable () async throws -> C,
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable (C.Element) async throws -> Void
-  ) -> Self where C: Collection & Sendable, C.Element: Sendable {
+  ) -> Self where S: ~Copyable, C: Collection & Sendable, C.Element: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -388,17 +388,17 @@ extension Test {
   ///
   /// - Warning: This function is used to implement the `@Test` macro. Do not
   ///   call it directly.
-  public static func __function<C1, C2>(
+  public static func __function<S, C1, C2>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: S.Type?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
     arguments collection1: @escaping @Sendable () async throws -> C1, _ collection2: @escaping @Sendable () async throws -> C2,
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable (C1.Element, C2.Element) async throws -> Void
-  ) -> Self where C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
+  ) -> Self where S: ~Copyable, C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -416,17 +416,17 @@ extension Test {
   ///
   /// - Warning: This function is used to implement the `@Test` macro. Do not
   ///   call it directly.
-  public static func __function<C, E1, E2>(
+  public static func __function<S, C, E1, E2>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: S.Type?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
     arguments collection: @escaping @Sendable () async throws -> C,
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable ((E1, E2)) async throws -> Void
-  ) -> Self where C: Collection & Sendable, C.Element == (E1, E2), E1: Sendable, E2: Sendable {
+  ) -> Self where S: ~Copyable, C: Collection & Sendable, C.Element == (E1, E2), E1: Sendable, E2: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -447,17 +447,17 @@ extension Test {
   ///
   /// - Warning: This function is used to implement the `@Test` macro. Do not
   ///   call it directly.
-  public static func __function<Key, Value>(
+  public static func __function<S, Key, Value>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: S.Type?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
     arguments dictionary: @escaping @Sendable () async throws -> Dictionary<Key, Value>,
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable ((Key, Value)) async throws -> Void
-  ) -> Self where Key: Sendable, Value: Sendable {
+  ) -> Self where S: ~Copyable, Key: Sendable, Value: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {
@@ -472,17 +472,17 @@ extension Test {
   ///
   /// - Warning: This function is used to implement the `@Test` macro. Do not
   ///   call it directly.
-  public static func __function<C1, C2>(
+  public static func __function<S, C1, C2>(
     named testFunctionName: String,
-    in containingType: (any ~Copyable.Type)?,
+    in containingType: S.Type?,
     xcTestCompatibleSelector: __XCTestCompatibleSelector?,
     displayName: String? = nil,
     traits: [any TestTrait],
     arguments zippedCollections: @escaping @Sendable () async throws -> Zip2Sequence<C1, C2>,
     sourceLocation: SourceLocation,
     parameters paramTuples: [__Parameter],
     testFunction: @escaping @Sendable (C1.Element, C2.Element) async throws -> Void
-  ) -> Self where C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
+  ) -> Self where S: ~Copyable, C1: Collection & Sendable, C1.Element: Sendable, C2: Collection & Sendable, C2.Element: Sendable {
     let containingTypeInfo: TypeInfo? = if let containingType {
       TypeInfo(describing: containingType)
     } else {

Sources/TestingMacros/TestDeclarationMacro.swift

@@ -382,7 +382,7 @@ public struct TestDeclarationMacro: PeerMacro, Sendable {
 
     // Get the name of the type containing the function for passing to the test
     // factory function later.
-    let typeNameExpr: ExprSyntax = typeName.map { "\($0).self" } ?? "nil"
+    let typeNameExpr: ExprSyntax = typeName.map { "\($0).self" } ?? "nil as Swift.Never.Type?"
 
     if typeName != nil, let genericGuardDecl = makeGenericGuardDecl(guardingAgainst: functionDecl, in: context) {
       result.append(genericGuardDecl)

Tests/TestingTests/MiscellaneousTests.swift

@@ -560,7 +560,7 @@ struct MiscellaneousTests {
     let line = 12345
     let column = 67890
     let sourceLocation = SourceLocation(fileID: fileID, filePath: filePath, line: line, column: column)
-    let testFunction = Test.__function(named: "myTestFunction()", in: nil, xcTestCompatibleSelector: nil, displayName: nil, traits: [], sourceLocation: sourceLocation) {}
+    let testFunction = Test.__function(named: "myTestFunction()", in: nil as Never.Type?, xcTestCompatibleSelector: nil, displayName: nil, traits: [], sourceLocation: sourceLocation) {}
     #expect(String(describing: testFunction.id) == "Module.myTestFunction()/Y.swift:12345:67890")
   }
 

Tests/TestingTests/SwiftPMTests.swift

@@ -285,7 +285,7 @@ struct SwiftPMTests {
   @Test("Unsupported ABI version")
   func unsupportedABIVersion() async throws {
     let versionNumber = VersionNumber(-100, 0)
-    let versionTypeInfo = ABI.version(forVersionNumber: versionNumber).map(TypeInfo.init(describing:))
+    let versionTypeInfo = ABI.version(forVersionNumber: versionNumber).map {TypeInfo(describing: $0) }
     #expect(versionTypeInfo == nil)
   }
 
@@ -294,7 +294,7 @@ struct SwiftPMTests {
     #expect(swiftCompilerVersion >= VersionNumber(6, 0))
     #expect(swiftCompilerVersion < VersionNumber(8, 0), "Swift 8.0 is here! Please update this test.")
     let versionNumber = VersionNumber(8, 0)
-    let versionTypeInfo = ABI.version(forVersionNumber: versionNumber).map(TypeInfo.init(describing:))
+    let versionTypeInfo = ABI.version(forVersionNumber: versionNumber).map {TypeInfo(describing: $0) }
     #expect(versionTypeInfo == nil)
   }
 

Tests/TestingTests/TypeInfoTests.swift

@@ -122,6 +122,11 @@ struct TypeInfoTests {
     #expect(!TypeInfo(describing: String.self).isSwiftEnumeration)
     #expect(TypeInfo(describing: SomeEnum.self).isSwiftEnumeration)
   }
+
+  @Test func typeOfMoveOnlyValueIsInferred() {
+    let value = MoveOnlyType()
+    #expect(TypeInfo(describingTypeOf: value).unqualifiedName == "MoveOnlyType")
+  }
 }
 
 // MARK: - Fixtures
@@ -131,3 +136,5 @@ extension String {
 }
 
 private enum SomeEnum {}
+
+private struct MoveOnlyType: ~Copyable {}