Add Swift Reflection Package (swiftlang#62819)

Author: Azoy

stdlib/public/Reflection/Package.swift

@@ -0,0 +1,62 @@
+// swift-tools-version: 5.7
+
+import PackageDescription
+
+let package = Package(
+  name: "Reflection",
+  platforms: [
+    .macOS(.v13)
+  ],
+  products: [
+    .library(
+      name: "Runtime",
+      type: .dynamic,
+      targets: ["Runtime"]
+    ),
+    .library(
+      name: "Reflection",
+      type: .dynamic,
+      targets: ["Reflection"]
+    ),
+  ],
+  targets: [
+    .target(
+      name: "CRuntime"
+    ),
+    .target(
+      name: "Runtime",
+      dependencies: ["CRuntime"],
+      swiftSettings: [
+        .unsafeFlags([
+          "-parse-stdlib",
+          "-enable-library-evolution",
+          "-Xfrontend", "-disable-implicit-concurrency-module-import",
+          "-Xfrontend", "-disable-implicit-string-processing-module-import",
+          "-assert-config", "Release"
+        ])
+      ]
+    ),
+    .target(
+      name: "Reflection",
+      dependencies: ["Runtime"],
+      swiftSettings: [
+        .unsafeFlags([
+          "-parse-stdlib",
+          "-enable-library-evolution",
+          "-Xfrontend", "-disable-implicit-concurrency-module-import",
+          "-Xfrontend", "-disable-implicit-string-processing-module-import",
+          "-assert-config", "Release"
+        ])
+      ]
+    ),
+    
+    .testTarget(
+      name: "RuntimeTests",
+      dependencies: ["Runtime"]
+    ),
+    .testTarget(
+      name: "ReflectionTests",
+      dependencies: ["Runtime", "Reflection"]
+    ),
+  ]
+)

stdlib/public/Reflection/README.md

@@ -0,0 +1,3 @@
+# Reflection
+
+A description of this package.

stdlib/public/Reflection/Sources/CRuntime/Functions.c

@@ -0,0 +1,12 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#include "include/Functions.h"

stdlib/public/Reflection/Sources/CRuntime/include/Functions.h

@@ -0,0 +1,22 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FUNCTIONS_H
+#define FUNCTIONS_H
+
+// OpaqueValue *swift_projectBox(HeapObject *object);
+extern void *swift_projectBox(void *object);
+
+// WitnessTable *swift_conformsToProtocol(Metadata *type,
+//                                        ProtocolDescriptor *protocol);
+extern void *swift_conformsToProtocol(const void *type, const void *protocol);
+
+#endif /* FUNCTIONS_H */

stdlib/public/Reflection/Sources/Reflection/Case.swift

@@ -0,0 +1,146 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import Swift
+import Runtime
+
+@frozen
+public struct Case {
+  @usableFromInline
+  let parent: EnumMetadata
+  
+  @usableFromInline
+  let tag: Int
+  
+  @inlinable
+  init(parent: EnumMetadata, tag: Int) {
+    self.parent = parent
+    self.tag = tag
+  }
+  
+  @inlinable
+  public init?(from instance: Any) {
+    guard Type(instance).isEnum else {
+      return nil
+    }
+    
+    var container = unsafeBitCast(instance, to: AnyExistentialContainer.self)
+    
+    let tag = container.projectValue {
+      Metadata(type(of: instance)).enum.enumVWT.getEnumTag($0)
+    }
+    
+    self.parent = Metadata(type(of: instance)).enum
+    self.tag = Int(truncatingIfNeeded: tag)
+  }
+}
+
+extension Case {
+  @inlinable
+  public var hasPayload: Bool {
+    tag < parent.descriptor.numberOfPayloadCases
+  }
+  
+  @inlinable
+  public var isIndirect: Bool {
+    parent.descriptor.type.fields[tag].flags.isIndirectCase
+  }
+  
+  @inlinable
+  public var name: String {
+    parent.descriptor.type.fields[tag].name
+  }
+  
+  @inlinable
+  public var payloadType: Type? {
+    guard tag < parent.descriptor.numberOfPayloadCases else {
+      return nil
+    }
+    
+    let typeRef = parent.descriptor.type.fields[tag].typeRef
+    
+    guard let resolved = parent.type.resolve(typeRef) else {
+      return nil
+    }
+    
+    return Type(resolved)
+  }
+}
+
+extension Case: CustomStringConvertible {
+  @inlinable
+  public var description: String {
+    var result = "\(unsafeBitCast(parent, to: Any.Type.self)).\(name)"
+    
+    if hasPayload {
+      let ty = payloadType!
+      
+      if ty.isTuple {
+        result += "\(ty)"
+      } else {
+        result += "(\(ty))"
+      }
+    }
+    
+    return result
+  }
+}
+
+@frozen
+public struct Cases {
+  @usableFromInline
+  let metadata: Metadata
+  
+  @inlinable
+  init(_ metadata: Metadata) {
+    self.metadata = metadata
+  }
+}
+
+extension Cases: RandomAccessCollection {
+  @inlinable
+  public var startIndex: Int {
+    0
+  }
+  
+  @inlinable
+  public var endIndex: Int {
+    guard Type(metadata).isEnum else {
+      return 0
+    }
+    
+    return metadata.enum.descriptor.numberOfCases
+  }
+  
+  @inlinable
+  public func index(after i: Int) -> Int {
+    i + 1
+  }
+  
+  @inlinable
+  public func index(before i: Int) -> Int {
+    i - 1
+  }
+  
+  @inlinable
+  public subscript(_ position: Int) -> Case {
+    precondition(position < endIndex)
+    
+    return Case(parent: metadata.enum, tag: position)
+  }
+}
+
+extension Type {
+  @inlinable
+  public var cases: Cases {
+    Cases(metadata)
+  }
+}