Merge pull request swiftlang#33445 from slavapestov/objc-protocols-have-a-layout-constraint

GSB: Add an inferred AnyObject constraint to @objc protocol requirement signatures

Author: slavapestov

lib/AST/ASTPrinter.cpp

@@ -1297,9 +1297,9 @@ bestRequirementPrintLocation(ProtocolDecl *proto, const Requirement &req) {
   bool inWhereClause;
 
   switch (req.getKind()) {
+  case RequirementKind::Layout:
   case RequirementKind::Conformance:
-  case RequirementKind::Superclass:
-  case RequirementKind::Layout: {
+  case RequirementKind::Superclass: {
     auto subject = req.getFirstType();
     auto result = findRelevantDeclAndDirectUse(subject);
 
@@ -1351,6 +1351,15 @@ void PrintAST::printInheritedFromRequirementSignature(ProtocolDecl *proto,
                             proto->getRequirementSignature()),
       PrintInherited,
       [&](const Requirement &req) {
+        // Skip the inferred 'Self : AnyObject' constraint if this is an
+        // @objc protocol.
+        if (req.getKind() == RequirementKind::Layout &&
+            req.getFirstType()->isEqual(proto->getProtocolSelfType()) &&
+            req.getLayoutConstraint()->getKind() == LayoutConstraintKind::Class &&
+            proto->isObjC()) {
+          return false;
+        }
+
         auto location = bestRequirementPrintLocation(proto, req);
         return location.AttachedTo == attachingTo && !location.InWhereClause;
       });

lib/AST/GenericSignature.cpp

@@ -404,16 +404,6 @@ bool GenericSignatureImpl::requiresClass(Type type) const {
   // If there is a layout constraint, it might be a class.
   if (equivClass->layout && equivClass->layout->isClass()) return true;
 
-  // If there is a superclass bound, then obviously it must be a class.
-  // FIXME: We shouldn't need this?
-  if (equivClass->superclass) return true;
-
-  // If any of the protocols are class-bound, then it must be a class.
-  // FIXME: We shouldn't need this?
-  for (const auto &conforms : equivClass->conformsTo) {
-    if (conforms.first->requiresClass()) return true;
-  }
-
   return false;
 }
 

lib/AST/GenericSignatureBuilder.cpp

@@ -3871,9 +3871,21 @@ ConstraintResult GenericSignatureBuilder::expandConformanceRequirement(
         return false;
       });
 
-  // Remaining logic is not relevant in ObjC protocol cases.
-  if (proto->isObjC())
+  if (proto->isObjC()) {
+    // @objc implies an inferred AnyObject constraint.
+    auto innerSource =
+      FloatingRequirementSource::viaProtocolRequirement(source, proto,
+                                                        /*inferred=*/true);
+    addLayoutRequirementDirect(selfType,
+                         LayoutConstraint::getLayoutConstraint(
+                             LayoutConstraintKind::Class,
+                             getASTContext()),
+                         innerSource);
+
     return ConstraintResult::Resolved;
+  }
+
+  // Remaining logic is not relevant in ObjC protocol cases.
 
   // Collect all of the inherited associated types and typealiases in the
   // inherited protocols (recursively).

lib/SIL/IR/SILFunctionType.cpp

@@ -1214,8 +1214,6 @@ class SubstFunctionTypeCollector {
         substRequirements.push_back(
                       Requirement(RequirementKind::Layout, param, layout));
       }
-    } else {
-      (void)0;
     }
 
     for (unsigned i : indices(upperBoundConformances)) {
@@ -1313,12 +1311,7 @@ class SubstFunctionTypeCollector {
             CanType binding,
             ArchetypeType *upperBound,
             ArrayRef<ProtocolConformanceRef> bindingConformances) -> CanType {
-          // TODO: ArchetypeType::getLayoutConstraint sometimes misses out on
-          // implied layout constraints. For now AnyObject is the only one we
-          // care about.
-          return addSubstitution(archetype->requiresClass()
-                                   ? LayoutConstraint::getLayoutConstraint(LayoutConstraintKind::Class)
-                                   : LayoutConstraint(),
+          return addSubstitution(archetype->getLayoutConstraint(),
                                  binding,
                                  upperBound,
                                  bindingConformances);

lib/Serialization/ModuleFormat.h

@@ -55,7 +55,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 570; // isUserAccessible
+const uint16_t SWIFTMODULE_VERSION_MINOR = 571; // @objc protocols get AnyObject constraint
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///

test/api-digester/Outputs/clang-module-dump.txt

@@ -43,6 +43,7 @@
       "declKind": "Protocol",
       "usr": "c:objc(pl)AnotherObjcProt",
       "moduleName": "Foo",
+      "genericSig": "<Self : AnyObject>",
       "objc_name": "AnotherObjcProt",
       "declAttributes": [
         "ObjC",
@@ -196,6 +197,7 @@
       "declKind": "Protocol",
       "usr": "c:objc(pl)ObjcProt",
       "moduleName": "Foo",
+      "genericSig": "<Self : AnyObject>",
       "objc_name": "ObjcProt",
       "declAttributes": [
         "ObjC",