Introduce SWIFT_ENABLE_REFLECTION to turn on/off the support for Mirrors and reflection

stdlib/CMakeLists.txt

@@ -102,6 +102,10 @@ set(SWIFT_STDLIB_ENABLE_LTO OFF CACHE STRING "Build Swift stdlib with LTO. One
     must specify the form of LTO by setting this to one of: 'full', 'thin'. This
     option only affects the standard library and runtime, not tools.")
 
+option(SWIFT_ENABLE_REFLECTION
+  "Build stdlib with support for runtime reflection and mirrors."
+  TRUE)
+
 #
 # End of user-configurable options.
 #

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -315,6 +315,10 @@ function(_add_target_variant_c_compile_flags)
     list(APPEND result "-DSWIFT_RUNTIME_NO_COMPATIBILITY_OVERRIDES")
   endif()
 
+  if(SWIFT_ENABLE_REFLECTION)
+    list(APPEND result "-DSWIFT_ENABLE_REFLECTION")
+  endif()
+
   if(SWIFT_RUNTIME_MACHO_NO_DYLD)
     list(APPEND result "-DSWIFT_RUNTIME_MACHO_NO_DYLD")
   endif()

stdlib/cmake/modules/SwiftSource.cmake

@@ -432,6 +432,12 @@ function(_compile_swift_files
     list(APPEND swift_flags "-Xfrontend" "-emit-sorted-sil")
   endif()
 
+  if(NOT SWIFT_ENABLE_REFLECTION)
+    list(APPEND swift_flags "-Xfrontend" "-disable-reflection-metadata")
+  else()
+    list(APPEND swift_flags "-D" "SWIFT_ENABLE_REFLECTION")
+  endif()
+
   # FIXME: Cleaner way to do this?
   if(SWIFTFILE_IS_STDLIB_CORE)
     list(APPEND swift_flags

stdlib/public/core/AnyHashable.swift

@@ -252,13 +252,15 @@ extension AnyHashable: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension AnyHashable: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(
       self,
       children: ["value": base])
   }
 }
+#endif
 
 @available(macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0, *)
 extension AnyHashable: _HasCustomAnyHashableRepresentation {

stdlib/public/core/Array.swift

@@ -1414,6 +1414,7 @@ extension Array {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Array: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1423,6 +1424,7 @@ extension Array: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension Array: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.

stdlib/public/core/ArraySlice.swift

@@ -1118,6 +1118,7 @@ extension ArraySlice: RangeReplaceableCollection {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ArraySlice: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1127,6 +1128,7 @@ extension ArraySlice: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension ArraySlice: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.

stdlib/public/core/ClosedRange.swift

@@ -396,12 +396,14 @@ extension ClosedRange: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ClosedRange: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(
       self, children: ["lowerBound": lowerBound, "upperBound": upperBound])
   }
 }
+#endif
 
 extension ClosedRange {
   /// Returns a copy of this range clamped to the given limiting range.

stdlib/public/core/CollectionOfOne.swift

@@ -165,11 +165,13 @@ extension CollectionOfOne: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension CollectionOfOne: CustomReflectable {
   public var customMirror: Mirror {
     return Mirror(self, children: ["element": _element])
   }
 }
+#endif
 
 extension CollectionOfOne: Sendable where Element: Sendable { }
 extension CollectionOfOne.Iterator: Sendable where Element: Sendable { }

stdlib/public/core/ContiguousArray.swift

@@ -1019,6 +1019,7 @@ extension ContiguousArray: RangeReplaceableCollection {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension ContiguousArray: CustomReflectable {
   /// A mirror that reflects the array.
   public var customMirror: Mirror {
@@ -1028,6 +1029,7 @@ extension ContiguousArray: CustomReflectable {
       displayStyle: .collection)
   }
 }
+#endif
 
 extension ContiguousArray: CustomStringConvertible, CustomDebugStringConvertible {
   /// A textual representation of the array and its elements.

stdlib/public/core/DebuggerSupport.swift

@@ -12,6 +12,8 @@
 
 import SwiftShims
 
+#if SWIFT_ENABLE_REFLECTION
+
 @frozen // namespace
 public enum _DebuggerSupport {
   private enum CollectionStatus {
@@ -262,6 +264,8 @@ public func _stringForPrintObject(_ value: Any) -> String {
   return _DebuggerSupport.stringForPrintObject(value)
 }
 
+#endif // SWIFT_ENABLE_REFLECTION
+
 public func _debuggerTestingCheckExpect(_: String, _: String) { }
 
 // Utilities to get refcount(s) of class objects.

stdlib/public/core/Dictionary.swift

@@ -2033,6 +2033,7 @@ extension Dictionary.Iterator: IteratorProtocol {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Dictionary.Iterator: CustomReflectable {
   /// A mirror that reflects the iterator.
   public var customMirror: Mirror {
@@ -2049,6 +2050,7 @@ extension Dictionary: CustomReflectable {
     return Mirror(self, unlabeledChildren: self, displayStyle: style)
   }
 }
+#endif
 
 extension Dictionary {
   /// Removes and returns the first key-value pair of the dictionary if the

stdlib/public/core/Dump.swift

@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if SWIFT_ENABLE_REFLECTION
+
 /// Dumps the given object's contents using its mirror to the specified output
 /// stream.
 ///
@@ -247,3 +249,4 @@ internal func _dumpSuperclass_unlocked<TargetStream: TextOutputStream>(
   }
 }
 
+#endif // SWIFT_ENABLE_REFLECTION

stdlib/public/core/MigrationSupport.swift

@@ -309,12 +309,14 @@ extension Substring {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Substring: _CustomPlaygroundQuickLookable {
   @available(swift, deprecated: 4.2/*, obsoleted: 5.0*/, message: "Substring.customPlaygroundQuickLook will be removed in a future Swift version")
   public var customPlaygroundQuickLook: _PlaygroundQuickLook {
     return String(self).customPlaygroundQuickLook
   }
 }
+#endif
 
 extension Collection {
   // FIXME: <rdar://problem/34142121>
@@ -630,6 +632,7 @@ public enum _PlaygroundQuickLook {
   case _raw([UInt8], String)
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension _PlaygroundQuickLook {
   /// Creates a new Quick Look for the given instance.
   ///
@@ -663,6 +666,7 @@ extension _PlaygroundQuickLook {
     }
   }
 }
+#endif
 
 /// A type that explicitly supplies its own playground Quick Look.
 ///

stdlib/public/core/Mirror.swift

@@ -12,6 +12,8 @@
 // FIXME: ExistentialCollection needs to be supported before this will work
 // without the ObjC Runtime.
 
+#if SWIFT_ENABLE_REFLECTION
+
 /// A representation of the substructure and display style of an instance of
 /// any type.
 ///
@@ -456,6 +458,70 @@ extension Mirror {
   }
 }
 
+#else  // SWIFT_ENABLE_REFLECTION
+
+@available(*, unavailable)
+public struct Mirror {
+  public enum AncestorRepresentation {
+    case generated
+    case customized(() -> Mirror)
+    case suppressed
+  }
+  public init(reflecting subject: Any) { Builtin.unreachable() }
+  public typealias Child = (label: String?, value: Any)
+  public typealias Children = AnyCollection<Child>
+  public enum DisplayStyle: Sendable {
+    case `struct`, `class`, `enum`, tuple, optional, collection
+    case dictionary, `set`
+  }
+  public init<Subject, C: Collection>(
+    _ subject: Subject,
+    children: C,
+    displayStyle: DisplayStyle? = nil,
+    ancestorRepresentation: AncestorRepresentation = .generated
+  ) where C.Element == Child { Builtin.unreachable() }
+  public init<Subject, C: Collection>(
+    _ subject: Subject,
+    unlabeledChildren: C,
+    displayStyle: DisplayStyle? = nil,
+    ancestorRepresentation: AncestorRepresentation = .generated
+  ) { Builtin.unreachable() }
+  public init<Subject>(
+    _ subject: Subject,
+    children: KeyValuePairs<String, Any>,
+    displayStyle: DisplayStyle? = nil,
+    ancestorRepresentation: AncestorRepresentation = .generated
+  ) { Builtin.unreachable() }
+  public let subjectType: Any.Type
+  public let children: Children
+  public let displayStyle: DisplayStyle?
+  public var superclassMirror: Mirror? { Builtin.unreachable() }
+}
+
+@available(*, unavailable)
+public protocol CustomReflectable {
+  var customMirror: Mirror { get }
+}
+
+@available(*, unavailable)
+public protocol CustomLeafReflectable: CustomReflectable {}
+
+@available(*, unavailable)
+public protocol MirrorPath {}
+@available(*, unavailable)
+extension Int: MirrorPath {}
+@available(*, unavailable)
+extension String: MirrorPath {}
+
+@available(*, unavailable)
+extension Mirror {
+  public func descendant(_ first: MirrorPath, _ rest: MirrorPath...) -> Any? {
+    Builtin.unreachable()
+  }
+}
+
+#endif  // SWIFT_ENABLE_REFLECTION
+
 //===--- General Utilities ------------------------------------------------===//
 
 extension String {
@@ -693,6 +759,8 @@ extension String {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
+
 /// Reflection for `Mirror` itself.
 extension Mirror: CustomStringConvertible {
   public var description: String {
@@ -705,3 +773,5 @@ extension Mirror: CustomReflectable {
     return Mirror(self, children: [:])
   }
 }
+
+#endif  // SWIFT_ENABLE_REFLECTION

stdlib/public/core/Mirrors.swift

@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if SWIFT_ENABLE_REFLECTION
+
 extension Float: CustomReflectable {
   /// A mirror that reflects the `Float` instance.
   public var customMirror: Mirror {
@@ -258,3 +260,5 @@ extension Float80: CustomReflectable {
   }
 }
 #endif
+
+#endif

stdlib/public/core/Optional.swift

@@ -279,6 +279,7 @@ extension Optional: CustomDebugStringConvertible {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 extension Optional: CustomReflectable {
   public var customMirror: Mirror {
     switch self {
@@ -292,6 +293,7 @@ extension Optional: CustomReflectable {
     }
   }
 }
+#endif
 
 @_transparent
 public // COMPILER_INTRINSIC

stdlib/public/core/OutputStream.swift

@@ -296,6 +296,7 @@ internal func _fallbackEnumRawValue<T>(_ value: T) -> Int64? {
   }
 }
 
+#if SWIFT_ENABLE_REFLECTION
 /// Do our best to print a value that cannot be printed directly.
 @_semantics("optimize.sil.specialize.generic.never")
 internal func _adHocPrint_unlocked<T, TargetStream: TextOutputStream>(
@@ -396,6 +397,7 @@ internal func _adHocPrint_unlocked<T, TargetStream: TextOutputStream>(
     }
   }
 }
+#endif
 
 @usableFromInline
 @_semantics("optimize.sil.specialize.generic.never")
@@ -435,8 +437,12 @@ internal func _print_unlocked<T, TargetStream: TextOutputStream>(
     return
   }
 
+#if SWIFT_ENABLE_REFLECTION
   let mirror = Mirror(reflecting: value)
   _adHocPrint_unlocked(value, mirror, &target, isDebugPrint: false)
+#else
+  target.write("(value cannot be printed without reflection)")
+#endif
 }
 
 //===----------------------------------------------------------------------===//
@@ -463,10 +469,15 @@ public func _debugPrint_unlocked<T, TargetStream: TextOutputStream>(
     return
   }
 
+#if SWIFT_ENABLE_REFLECTION
   let mirror = Mirror(reflecting: value)
   _adHocPrint_unlocked(value, mirror, &target, isDebugPrint: true)
+#else
+  target.write("(value cannot be printed without reflection)")
+#endif
 }
 
+#if SWIFT_ENABLE_REFLECTION
 @_semantics("optimize.sil.specialize.generic.never")
 internal func _dumpPrint_unlocked<T, TargetStream: TextOutputStream>(
     _ value: T, _ mirror: Mirror, _ target: inout TargetStream
@@ -533,6 +544,7 @@ internal func _dumpPrint_unlocked<T, TargetStream: TextOutputStream>(
 
   _adHocPrint_unlocked(value, mirror, &target, isDebugPrint: true)
 }
+#endif
 
 //===----------------------------------------------------------------------===//
 // OutputStreams