Use generics to declare suite types in macro expansions.

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.

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 +88,9 @@ 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: borrowing some ~Copyable) {
+    let type = Swift.type(of: value)
+    self.init(describing: type)
   }
 }
 

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")
   }