Merge remote-tracking branch 'origin/master' into master-rebranch

Author: swift-ci

include/swift/ABI/MetadataValues.h

@@ -672,7 +672,7 @@ class ExistentialTypeFlags {
 private:
   enum : int_type {
     NumWitnessTablesMask  = 0x00FFFFFFU,
-    ClassConstraintMask   = 0x80000000U,
+    ClassConstraintMask   = 0x80000000U, // Warning: Set if NOT class-constrained!
     HasSuperclassMask     = 0x40000000U,
     SpecialProtocolMask   = 0x3F000000U,
     SpecialProtocolShift  = 24U,

stdlib/public/runtime/Casting.cpp

@@ -1878,18 +1878,44 @@ static bool tryDynamicCastBoxedSwiftValue(OpaqueValue *dest,
   assert(!(flags & DynamicCastFlags::Unconditional));
   assert(!(flags & DynamicCastFlags::DestroyOnFailure));
 
+  auto originalSrc = src;
+  auto originalSrcType = srcType;
+
   // Swift type should be AnyObject or a class type.
-  if (!srcType->isAnyClass()) {
-    auto existential = dyn_cast<ExistentialTypeMetadata>(srcType);
-    if (!existential || !isAnyObjectExistentialType(existential))
+  while (true) {
+    if (srcType->isAnyClass()) {
+      break;
+    }
+    auto existentialType = dyn_cast<ExistentialTypeMetadata>(srcType);
+    if (!existentialType)
+      return false;
+    switch (existentialType->getRepresentation()) {
+    case ExistentialTypeRepresentation::Class: {
+      // If it's a Class object, it must be `AnyObject`
+      if (isAnyObjectExistentialType(existentialType)) {
+        goto validated;
+      }
+      return false;
+    }
+    case ExistentialTypeRepresentation::Opaque: {
+      // If it's an opaque existential, unwrap it and check again
+      auto opaqueContainer = reinterpret_cast<OpaqueExistentialContainer*>(src);
+      srcType = opaqueContainer->Type;
+      src = existentialType->projectValue(src);
+      break;
+    }
+    default: {
       return false;
+    }
+    }
   }
+  validated:
 
 #if !SWIFT_OBJC_INTEROP // __SwiftValue is a native class:
   if (swift_unboxFromSwiftValueWithType(src, dest, targetType)) {
     // Release the source if we need to.
     if (flags & DynamicCastFlags::TakeOnSuccess)
-      srcType->vw_destroy(src);
+      originalSrcType->vw_destroy(originalSrc);
     return true;
   }
 #endif
@@ -1919,7 +1945,7 @@ static bool tryDynamicCastBoxedSwiftValue(OpaqueValue *dest,
                                       const_cast<OpaqueValue*>(boxedValue));
     // Release the box if we need to.
     if (flags & DynamicCastFlags::TakeOnSuccess)
-      objc_release((id)srcSwiftValue);
+      originalSrcType->vw_destroy(originalSrc);
     return true;
   }
 
@@ -1931,7 +1957,7 @@ static bool tryDynamicCastBoxedSwiftValue(OpaqueValue *dest,
                         boxedType, targetType, innerFlags)) {
     // Release the box if we need to.
     if (flags & DynamicCastFlags::TakeOnSuccess)
-      objc_release((id)srcSwiftValue);
+      originalSrcType->vw_destroy(originalSrc);
     return true;
   }
 #endif

test/stdlib/Casts.swift

@@ -80,6 +80,46 @@ CastsTests.test("Optional<T>.none can be casted to Optional<U>.none in generic c
   expectEqual(type(of: test(Bool?.self)), Bool??.self)
 }
 
+// Test for SR-3871: Cannot cast from ObjC existential without going through AnyObject
+#if _runtime(_ObjC)
+protocol P2 {}
+CastsTests.test("Cast from ObjC existential to Protocol (SR-3871)") {
+  struct S: P2 {}
+
+  class ObjCWrapper {
+    @objc dynamic let any: Any = S()
+    init() {}
+  }
+  let a = ObjCWrapper().any
+  expectTrue(a is P2)
+  // In SR-3871, the following cast failed (everything else here succeeded)
+  expectNotNil(a as? P2)
+  expectNotNil(a as? S)
+  let b = a as AnyObject
+  expectTrue(a is P2)
+  expectNotNil(b as? P2)
+  expectNotNil(b as? S)
+}
+#endif
+
+protocol P3 {}
+CastsTests.test("Cast from Swift existential to Protocol") {
+  struct S: P3 {}
+  class SwiftWrapper {
+    let any: Any = S()
+    init() {}
+  }
+  let a = SwiftWrapper().any
+  expectTrue(a is P3)
+  expectNotNil(a as? P3)
+  expectNotNil(a as? S)
+  let b = a as AnyObject
+  expectTrue(b is P3)
+  expectNotNil(b as? P3)
+  expectNotNil(b as? S)
+}
+
+
 #if _runtime(_ObjC)
 extension CFBitVector : P {
   static func makeImmutable(from values: Array<UInt8>) -> CFBitVector {