stdlib: Rewrite _getClassPlaygroundQuickLook() in Swift

The C++ code was very fragile in terms of ABI dependencies and broke
when the standard library was built with -enable-resilience.

The actual reason it broke is that case numbering changes when
resilience is enabled, but instead of messing with that, it seemed
more logical to rewrite this routine in Swift instead, to avoid
ABI dependencies altogether.

This requires using the "shadow protocol" trick to call NSNumber
methods, since we cannot import NSNumber from the stdlib.

Author: slavapestov

stdlib/public/core/Mirror.swift

@@ -573,15 +573,6 @@ internal extension Mirror {
 
 /// The sum of types that can be used as a quick look representation.
 public enum PlaygroundQuickLook {
-  //
-  // This type must be binary-compatible with the 'PlaygroundQuickLook' struct
-  // in stdlib/public/runtime/Reflection.mm, and 'PlaygroundQuickLook?' must be
-  // binary compatible with 'OptionalPlaygroundQuickLook' from the same.
-  //
-  // NB: This type is somewhat carefully laid out to *suppress* enum layout
-  // optimization so that it is easier to manufacture in the C++ runtime
-  // implementation.
-
   /// Plain text.
   case text(String)
 

stdlib/public/core/ObjCMirrors.swift

@@ -42,9 +42,8 @@ struct _ObjCMirror : _Mirror {
     return _getObjCSummary(data)
   }
   public var quickLookObject: PlaygroundQuickLook? {
-    var result: PlaygroundQuickLook? = nil
-    _getClassPlaygroundQuickLook(&result, data)
-    return result
+    let object = _swift_ClassMirror_quickLookObject(data)
+    return _getClassPlaygroundQuickLook(object)
   }
   public var disposition: _MirrorDisposition { return .objCObject }
 }
@@ -70,9 +69,8 @@ struct _ObjCSuperMirror : _Mirror {
     return _getObjCSummary(data)
   }
   public var quickLookObject: PlaygroundQuickLook? {
-    var result: PlaygroundQuickLook? = nil
-    _getClassPlaygroundQuickLook(&result, data)
-    return result
+    let object = _swift_ClassMirror_quickLookObject(data)
+    return _getClassPlaygroundQuickLook(object)
   }
   public var disposition: _MirrorDisposition { return .objCObject }
 }

stdlib/public/core/Reflection.swift

@@ -520,10 +520,50 @@ func _getClassChild<T>(_: Int, _: _MagicMirrorData) -> (T, _Mirror)
 
 #if _runtime(_ObjC)
 @_silgen_name("swift_ClassMirror_quickLookObject")
-public func _getClassPlaygroundQuickLook(
-  _: inout PlaygroundQuickLook?,
-  _: _MagicMirrorData
-)
+public func _swift_ClassMirror_quickLookObject(_: _MagicMirrorData) -> AnyObject
+
+@_silgen_name("swift_isKind")
+func _swift_isKind(object: AnyObject, of: AnyObject) -> Bool
+
+func _isKind(object: AnyObject, of: String) -> Bool {
+  return _swift_isKind(object, of: _bridgeToObjectiveC(of)!)
+}
+
+func _getClassPlaygroundQuickLook(object: AnyObject) -> PlaygroundQuickLook? {
+  if _isKind(object, of: "NSNumber") {
+    let number: _NSNumber = unsafeBitCast(object, to: _NSNumber.self)
+    switch UInt8(number.objCType[0]) {
+    case UInt8(ascii: "d"):
+      return .double(number.doubleValue)
+    case UInt8(ascii: "f"):
+      return .float(number.floatValue)
+    case UInt8(ascii: "Q"):
+      return .uInt(number.unsignedLongLongValue)
+    default:
+      return .int(number.longLongValue)
+    }
+  } else if _isKind(object, of: "NSAttributedString") {
+    return .attributedString(object)
+  } else if _isKind(object, of: "NSImage") ||
+            _isKind(object, of: "UIImage") ||
+            _isKind(object, of: "NSImageView") ||
+            _isKind(object, of: "UIImageView") ||
+            _isKind(object, of: "CIImage") ||
+            _isKind(object, of: "NSBitmapImageRep") {
+    return .image(object)
+  } else if _isKind(object, of: "NSColor") ||
+            _isKind(object, of: "UIColor") {
+    return .color(object)
+  } else if _isKind(object, of: "NSBezierPath") ||
+            _isKind(object, of: "UIBezierPath") {
+    return .bezierPath(object)
+  } else if _isKind(object, of: "NSString") {
+    return .text(_forceBridgeFromObjectiveC(object, String.self))
+  }
+
+  return .none
+}
+
 #endif
 
 struct _ClassMirror : _Mirror {
@@ -545,9 +585,8 @@ struct _ClassMirror : _Mirror {
   }
   var quickLookObject: PlaygroundQuickLook? {
 #if _runtime(_ObjC)
-    var result: PlaygroundQuickLook? = nil
-    _getClassPlaygroundQuickLook(&result, data)
-    return result
+    let object = _swift_ClassMirror_quickLookObject(data)
+    return _getClassPlaygroundQuickLook(object)
 #else
     return nil
 #endif

stdlib/public/core/ShadowProtocols.swift

@@ -171,6 +171,17 @@ public protocol _NSSetCore :
 public protocol _NSSet : _NSSetCore {
 }
 
+/// A shadow for the API of NSNumber we will use in the core
+/// stdlib.
+@objc
+public protocol _NSNumber {
+  var doubleValue: Double { get }
+  var floatValue: Float { get }
+  var unsignedLongLongValue: UInt64 { get }
+  var longLongValue: Int64 { get }
+  var objCType: UnsafePointer<Int8> { get }
+}
+
 #else
 
 public protocol _NSArrayCore {}

stdlib/public/runtime/Reflection.mm

@@ -112,86 +112,7 @@ explicit String(NSString *s)
   {}
 #endif
 };
-  
-struct Array {
-  // Keep the details of Array's implementation opaque to the runtime.
-  const void *x;
-};
-  
-struct PlaygroundQuickLook {
-  struct RawData {
-    Array Data;
-    String Type;
-  };
-  struct Rectangle {
-    double x, y, w, h;
-  };
-  struct Point {
-    double x, y;
-  };
-  struct Interval {
-    int64_t loc,len;
-  };
-  
-  union {
-    String TextOrURL;
-    int64_t Int;
-    uint64_t UInt;
-    float Float;
-    double Double;
-    Any Any;
-    RawData Raw;
-    Rectangle Rect;
-    Point PointOrSize;
-    bool Logical;
-    Interval Range;
-  };
-  enum class Tag : uint8_t {
-    Text,
-    Int,
-    UInt,
-    Float,
-    Double,
-    Image,
-    Sound,
-    Color,
-    BezierPath,
-    AttributedString,
-    Rectangle,
-    Point,
-    Size,
-    Logical,
-    Range,
-    View,
-    Sprite,
-    URL,
-    Raw,
-  } Kind;
-};
-  
-struct OptionalPlaygroundQuickLook {
-  union {
-    struct {
-      union {
-        String TextOrURL;
-        int64_t Int;
-        uint64_t UInt;
-        float Float;
-        double Double;
-        Any Any;
-        PlaygroundQuickLook::RawData Raw;
-        PlaygroundQuickLook::Rectangle Rect;
-        PlaygroundQuickLook::Point PointOrSize;
-        bool Logical;
-        PlaygroundQuickLook::Interval Range;
-      };
-      PlaygroundQuickLook::Tag Kind;
-      bool isNone;
-    } optional;
-    PlaygroundQuickLook payload;
-  };
-};
-  
+
 /// A Mirror witness table for use by MagicMirror.
 struct MirrorWitnessTable;
 
@@ -980,99 +901,30 @@ void swift_ObjCMirror_subscript(String *outString,
 }
 
 SWIFT_RUNTIME_STDLIB_INTERFACE
-extern "C" void
-swift_ClassMirror_quickLookObject(OptionalPlaygroundQuickLook &result,
-                                  HeapObject *owner, const OpaqueValue *value,
+extern "C" id
+swift_ClassMirror_quickLookObject(HeapObject *owner, const OpaqueValue *value,
                                   const Metadata *type) {
-  memset(&result, 0, sizeof(result));
-  
   id object = [*reinterpret_cast<const id *>(value) retain];
   swift_release(owner);
   if ([object respondsToSelector:@selector(debugQuickLookObject)]) {
     id quickLookObject = [object debugQuickLookObject];
     [quickLookObject retain];
     [object release];
-    object = quickLookObject;
+    return quickLookObject;
   }
-  
-  // NSNumbers quick-look as integers or doubles, depending on type.
-  if ([object isKindOfClass:[NSNumber class]]) {
-    NSNumber *n = object;
-    
-    switch ([n objCType][0]) {
-    case 'd': // double
-      result.payload.Double = [n doubleValue];
-      result.payload.Kind = PlaygroundQuickLook::Tag::Double;
-      break;
-    case 'f': // float
-      result.payload.Float = [n floatValue];
-      result.payload.Kind = PlaygroundQuickLook::Tag::Float;
-      break;
-        
-    case 'Q': // unsigned long long
-      result.payload.UInt = [n unsignedLongLongValue];
-      result.payload.Kind = PlaygroundQuickLook::Tag::UInt;
-      break;
 
-    // FIXME: decimals?
-    default:
-      result.payload.Int = [n longLongValue];
-      result.payload.Kind = PlaygroundQuickLook::Tag::Int;
-      break;
-    }
-    
-    [object release];
-    result.optional.isNone = false;
-    return;
-  }
-  
-  // Various other framework types are used for rich representations.
-  
-  /// Store an ObjC reference into an Any.
-  auto initializeAnyWithTakeOfObject = [](Any &any, id obj) {
-    any.Type = swift_getObjCClassMetadata(_swift_getClass((const void*) obj));
-    *reinterpret_cast<id *>(&any.Buffer) = obj;
-  };
-  
-  if ([object isKindOfClass:NSClassFromString(@"NSAttributedString")]) {
-    initializeAnyWithTakeOfObject(result.payload.Any, object);
-    result.payload.Kind = PlaygroundQuickLook::Tag::AttributedString;
-    result.optional.isNone = false;
-    return;
-  } else if ([object isKindOfClass:NSClassFromString(@"NSImage")]
-      || [object isKindOfClass:NSClassFromString(@"UIImage")]
-      || [object isKindOfClass:NSClassFromString(@"NSImageView")]
-      || [object isKindOfClass:NSClassFromString(@"UIImageView")]
-      || [object isKindOfClass:NSClassFromString(@"CIImage")]
-      || [object isKindOfClass:NSClassFromString(@"NSBitmapImageRep")]) {
-    initializeAnyWithTakeOfObject(result.payload.Any, object);
-    result.payload.Kind = PlaygroundQuickLook::Tag::Image;
-    result.optional.isNone = false;
-    return;
-  } else if ([object isKindOfClass:NSClassFromString(@"NSColor")]
-             || [object isKindOfClass:NSClassFromString(@"UIColor")]) {
-    initializeAnyWithTakeOfObject(result.payload.Any, object);
-    result.payload.Kind = PlaygroundQuickLook::Tag::Color;
-    result.optional.isNone = false;
-    return;
-  } else if ([object isKindOfClass:NSClassFromString(@"NSBezierPath")]
-             || [object isKindOfClass:NSClassFromString(@"UIBezierPath")]) {
-    initializeAnyWithTakeOfObject(result.payload.Any, object);
-    result.payload.Kind = PlaygroundQuickLook::Tag::BezierPath;
-    result.optional.isNone = false;
-    return;
-  } else if ([object isKindOfClass:[NSString class]]) {
-    result.payload.TextOrURL = String((NSString*)object);
-    [object release];
-    result.payload.Kind = PlaygroundQuickLook::Tag::Text;
-    result.optional.isNone = false;
-    return;
-  }
-  
-  // Return none if we didn't get a suitable object.
+  return object;
+}
+
+SWIFT_RUNTIME_STDLIB_INTERFACE
+extern "C" bool swift_isKind(id object, NSString *className) {
+  bool result = [object isKindOfClass:NSClassFromString(className)];
   [object release];
-  result.optional.isNone = true;
+  [className release];
+
+  return result;
 }
+
 #endif
 
 // -- MagicMirror implementation.