Merge pull request #42077 from DougGregor/implicit-opening-cleanups

Author: DougGregor

lib/Sema/CSSimplify.cpp

@@ -1421,6 +1421,18 @@ namespace {
     OptionSet<OpenedExistentialAdjustmentFlags>;
 }
 
+/// Determine if this function is part of the _isUnique family of functions in
+/// the standard library.
+static bool isStdlibUniqueFunction(ValueDecl *callee) {
+  if (!callee->isStdlibDecl())
+    return false;
+
+  auto baseName = callee->getName().getBaseName().userFacingName();
+  return baseName ==  "_isUnique" || baseName == "_isUnique_native" ||
+         baseName == "_COWBufferForReading" ||
+         baseName == "_unsafeDowncastToAnyObject";
+}
+
 /// Determine whether we should open up the existential argument to the
 /// given parameters.
 ///
@@ -1457,6 +1469,14 @@ shouldOpenExistentialCallArgument(
     return None;
 
   case DeclTypeCheckingSemantics::Normal:
+    // _isUnique and friends are special because opening an existential when
+    // calling them would make them non-unique.
+    // FIXME: Borrowing properly from the existential box would probably
+    // eliminate this.
+    if (isStdlibUniqueFunction(callee))
+      return None;
+    break;
+
   case DeclTypeCheckingSemantics::WithoutActuallyEscaping:
     break;
   }
@@ -1501,15 +1521,22 @@ shouldOpenExistentialCallArgument(
   if (!argTy->isAnyExistentialType())
     return None;
 
-  if (argTy->isExistentialType()) {
-    // If the existential argument type conforms to all of its protocol
-    // requirements, don't open the existential.
-    auto layout = argTy->getExistentialLayout();
+
+  // If the existential argument type conforms to all of its protocol
+  // requirements, don't open the existential.
+  {
+    Type existentialObjectType;
+    if (auto existentialMetaTy = argTy->getAs<ExistentialMetatypeType>())
+      existentialObjectType = existentialMetaTy->getInstanceType();
+    else
+      existentialObjectType = argTy;
+    auto layout = existentialObjectType->getExistentialLayout();
     auto module = cs.DC->getParentModule();
     bool containsNonSelfConformance = false;
     for (auto proto : layout.getProtocols()) {
       auto protoDecl = proto->getDecl();
-      auto conformance = module->lookupExistentialConformance(argTy, protoDecl);
+      auto conformance = module->lookupExistentialConformance(
+          existentialObjectType, protoDecl);
       if (conformance.isInvalid()) {
         containsNonSelfConformance = true;
         break;

test/Constraints/opened_existentials_suppression.swift

@@ -4,6 +4,7 @@ protocol P { }
 extension Optional: P where Wrapped: P { }
 
 func acceptsBox<T>(_ value: T) { }
+func acceptsBoxType<T>(_ value: T.Type) { }
 
 // CHECK: passBox
 // CHECK-NOT: open_existential_expr
@@ -13,4 +14,6 @@ func passBox(p: P, obj: AnyObject, err: Error) {
   acceptsBox(p as? P)
   acceptsBox(obj)
   acceptsBox(err)
+  acceptsBoxType(Any.self)
+  acceptsBoxType(AnyObject.self)
 }