SR-7732: Dynamic casting CFError to Error results in a memory leak (#28686)

* SR-7732: Dynamic casting CFError to Error results in a memory leak

The special handling for casting CFError/NSError to Swift Error
type was using cleanup code that didn't correctly handle this case.
This replaces the cleanup code with a more targeted version.

Fixes: SR-7732
Fixes: rdar://problem/40423061

* Whitespace fixes

* Don't rely on localizable strings to verify test behavior.

I've verified this simplified test still leaks with
the original code and does not leak with the fixed code.

* Don't test against old runtimes that predate this fix

* Explicitly test both NSError and CFError

Author: tbkka

stdlib/public/runtime/Casting.cpp

@@ -911,7 +911,9 @@ static bool _dynamicCastToExistential(OpaqueValue *dest,
                                                         srcDynamicType,
                                                         errorWitness)) {
       *destBoxAddr = reinterpret_cast<SwiftError*>(embedded);
-      maybeDeallocateSource(true);
+      if (shouldDeallocateSource(true, flags)) {
+        srcType->vw_destroy(src);
+      }
       return true;
     }
 #endif

test/stdlib/ErrorBridged.swift

@@ -684,9 +684,9 @@ ErrorBridgingTests.test("Wrapped NSError identity") {
 }
 
 extension Error {
-	func asNSError() -> NSError {
-		return self as NSError
-	}
+  func asNSError() -> NSError {
+    return self as NSError
+  }
 }
 
 func unconditionalCast<T>(_ x: Any, to: T.Type) -> T {
@@ -788,4 +788,31 @@ ErrorBridgingTests.test("error-to-NSObject casts") {
   }
 }
 
+// SR-7732: Casting CFError or NSError to Error results in a memory leak
+ErrorBridgingTests.test("NSError-to-Error casts") {
+  func should_not_leak_nserror() {
+    let something: Any? = NSError(domain: "Foo", code: 1)
+    expectTrue(something is Error)
+  }
+
+  if #available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *) {
+    // TODO: Wrap some leak checking around this
+    // Until then, this is a helpful debug tool
+		should_not_leak_nserror()
+  }
+}
+
+ErrorBridgingTests.test("CFError-to-Error casts") {
+  func should_not_leak_cferror() {
+    let something: Any? = CFErrorCreate(kCFAllocatorDefault, kCFErrorDomainCocoa, 1, [:] as CFDictionary)
+    expectTrue(something is Error)
+  }
+
+  if #available(macOS 9999, iOS 9999, tvOS 9999, watchOS 9999, *) {
+    // TODO: Wrap some leak checking around this
+    // Until then, this is a helpful debug tool
+		should_not_leak_cferror()
+  }
+}
+
 runAllTests()