Merge pull request #17851 from slavapestov/protocol-superclass-part-4

Protocol superclass constraints part 4

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -1833,6 +1833,10 @@ WARNING(protocol_composition_with_postfix,none,
         "protocol-constrained type with postfix '%0' is ambiguous "
         "and will be rejected in future version of Swift", (StringRef))
 
+ERROR(protocol_where_clause_self_requirement,none,
+      "constraint with subject type of 'Self' is not supported; "
+      "consider adding requirement to protocol inheritance clause instead", ())
+
 ERROR(invalid_protocol_composition_member,none,
       "non-protocol, non-class type %0 cannot be used within a "
       "protocol-constrained type", (Type))
@@ -2128,6 +2132,8 @@ ERROR(duplicate_inheritance,none,
   "duplicate inheritance from %0", (Type))
 WARNING(duplicate_anyobject_class_inheritance,none,
   "redundant inheritance from 'AnyObject' and Swift 3 'class' keyword", ())
+ERROR(objc_protocol_with_superclass,none,
+  "protocol %0 is '@objc' and cannot have a superclass constraint", (Identifier))
 ERROR(multiple_inheritance,none,
   "multiple inheritance from classes %0 and %1", (Type, Type))
 ERROR(non_class_inheritance,none,

lib/IRGen/ClassMetadataVisitor.h

@@ -61,7 +61,7 @@ template <class Impl> class ClassMetadataVisitor
     // isn't necessary.
     // FIXME: Figure out what can be removed altogether in non-objc-interop
     // mode and remove it. rdar://problem/18801263
-    asImpl().addSuperClass();
+    asImpl().addSuperclass();
     asImpl().addClassCacheData();
     asImpl().addClassDataPointer();
 
@@ -171,7 +171,7 @@ class ClassMetadataScanner : public ClassMetadataVisitor<Impl> {
   void addIVarDestroyer() { addPointer(); }
   void addValueWitnessTable() { addPointer(); }
   void addDestructorFunction() { addPointer(); }
-  void addSuperClass() { addPointer(); }
+  void addSuperclass() { addPointer(); }
   void addClassFlags() { addInt32(); }
   void addInstanceAddressPoint() { addInt32(); }
   void addInstanceSize() { addInt32(); }

lib/IRGen/ForeignClassMetadataVisitor.h

@@ -38,7 +38,7 @@ class ForeignClassMetadataVisitor
     super::layout();
     asImpl().addNominalTypeDescriptor();
     asImpl().noteStartOfSuperClass();
-    asImpl().addSuperClass();
+    asImpl().addSuperclass();
     asImpl().addReservedWord();
     asImpl().addReservedWord();
     asImpl().addReservedWord();
@@ -70,7 +70,7 @@ class ForeignClassMetadataScanner : public ForeignClassMetadataVisitor<Impl> {
   void addMetadataFlags() { addPointer(); }
   void addValueWitnessTable() { addPointer(); }
   void addNominalTypeDescriptor() { addPointer(); }
-  void addSuperClass() { addPointer(); }
+  void addSuperclass() { addPointer(); }
   void addReservedWord() { addPointer(); }
 
 private:

lib/IRGen/GenCast.cpp

@@ -522,7 +522,7 @@ void irgen::emitScalarExistentialDowncast(IRGenFunction &IGF,
   bool hasClassConstraint = layout.requiresClass();
   bool hasClassConstraintByProtocol = false;
 
-  bool hasSuperclassConstraint = bool(layout.getSuperclass());
+  bool hasSuperclassConstraint = bool(layout.explicitSuperclass);
 
   for (auto protoTy : layout.getProtocols()) {
     auto *protoDecl = protoTy->getDecl();
@@ -581,9 +581,17 @@ void irgen::emitScalarExistentialDowncast(IRGenFunction &IGF,
   // Note that destInstanceType is always an existential type, so calling
   // getSuperclass() returns the superclass constraint of the existential,
   // not the superclass of some concrete class.
-  bool checkSuperclassConstraint =
-    hasSuperclassConstraint &&
-    !destInstanceType->getSuperclass()->isExactSuperclassOf(srcInstanceType);
+  bool checkSuperclassConstraint = false;
+  if (hasSuperclassConstraint) {
+    Type srcSuperclassType = srcInstanceType;
+    if (srcSuperclassType->isExistentialType())
+      srcSuperclassType = srcSuperclassType->getSuperclass();
+    if (srcSuperclassType) {
+      checkSuperclassConstraint =
+        !destInstanceType->getSuperclass()->isExactSuperclassOf(
+          srcSuperclassType);
+    }
+  }
 
   if (checkSuperclassConstraint)
     checkClassConstraint = true;
@@ -739,7 +747,7 @@ void irgen::emitScalarExistentialDowncast(IRGenFunction &IGF,
   args.push_back(metadataValue);
 
   if (checkSuperclassConstraint)
-    args.push_back(IGF.emitTypeMetadataRef(CanType(layout.getSuperclass())));
+    args.push_back(IGF.emitTypeMetadataRef(CanType(layout.explicitSuperclass)));
 
   for (auto proto : witnessTableProtos)
     args.push_back(proto);

lib/IRGen/GenMeta.cpp

@@ -2041,7 +2041,7 @@ namespace {
       AddressPoint = B.getNextOffsetFromGlobal();
     }
 
-    void addSuperClass() {
+    void addSuperclass() {
       // If this is a root class, use SwiftObject as our formal parent.
       if (!Target->hasSuperclass()) {
         // This is only required for ObjC interoperation.
@@ -3246,7 +3246,7 @@ namespace {
 
     void noteStartOfSuperClass() { }
 
-    void addSuperClass() {
+    void addSuperclass() {
       auto superclassDecl = Target->getSuperclassDecl();
       if (!superclassDecl || !superclassDecl->isForeign()) {
         B.addNullPointer(IGM.TypeMetadataPtrTy);

lib/Sema/TypeCheckDecl.cpp

@@ -214,6 +214,8 @@ void TypeChecker::validateWhereClauses(ProtocolDecl *protocol,
                                        GenericTypeResolver *resolver) {
   TypeResolutionOptions options;
 
+  options |= TypeResolutionFlags::ProtocolWhereClause;
+
   if (auto whereClause = protocol->getTrailingWhereClause()) {
     revertGenericRequirements(whereClause->getRequirements());
     validateRequirements(whereClause->getWhereLoc(),
@@ -288,9 +290,7 @@ void TypeChecker::checkInheritanceClause(Decl *decl,
     inheritedClause = type->getInherited();
   } else {
     auto ext = cast<ExtensionDecl>(decl);
-
-    validateExtension(ext);
-    if (ext->isInvalid())
+    if (!ext->getExtendedType())
       return;
 
     inheritedClause = ext->getInherited();
@@ -408,17 +408,27 @@ void TypeChecker::checkInheritanceClause(Decl *decl,
     }
     inheritedTypes[inheritedCanTy] = { i, inherited.getSourceRange() };
 
-    // If this is a protocol or protocol composition type, record the
-    // protocols.
     if (inheritedTy->isExistentialType()) {
       auto layout = inheritedTy->getExistentialLayout();
 
+      // @objc protocols cannot have superclass constraints.
+      if (layout.explicitSuperclass) {
+        if (auto *protoDecl = dyn_cast<ProtocolDecl>(decl)) {
+          if (protoDecl->isObjC()) {
+            diagnose(protoDecl,
+                    diag::objc_protocol_with_superclass,
+                    protoDecl->getName());
+            continue;
+          }
+        }
+      }
+
       // Protocols, generic parameters and associated types can inherit
       // from subclass existentials, which are "exploded" into their
       // corresponding requirements.
       //
-      // Classes can only inherit from subclass existentials that do not
-      // have a superclass term.
+      // Extensions, structs and enums can only inherit from protocol
+      // compositions that do not contain AnyObject or class members.
       if (isa<ProtocolDecl>(decl) ||
           isa<AbstractTypeParamDecl>(decl) ||
           (!layout.hasExplicitAnyObject &&
@@ -494,6 +504,16 @@ void TypeChecker::checkInheritanceClause(Decl *decl,
         continue;
       }
 
+      // @objc protocols cannot have superclass constraints.
+      if (auto *protoDecl = dyn_cast<ProtocolDecl>(decl)) {
+        if (protoDecl->isObjC()) {
+          diagnose(protoDecl,
+                   diag::objc_protocol_with_superclass,
+                   protoDecl->getName());
+          continue;
+        }
+      }
+
       // If the declaration we're looking at doesn't allow a superclass,
       // complain.
       if (isa<StructDecl>(decl) || isa<ExtensionDecl>(decl)) {

lib/Sema/TypeCheckGeneric.cpp

@@ -310,6 +310,31 @@ bool TypeChecker::validateRequirement(SourceLoc whereLoc, RequirementRepr &req,
   // Note that we are resolving within a requirement.
   options |= TypeResolutionFlags::GenericRequirement;
 
+  // Protocol where clauses cannot add conformance and superclass constraints
+  // to 'Self', because we need to be able to resolve inherited protocols and
+  // protocol superclasses before computing the protocol requirement signature.
+  if (options & TypeResolutionFlags::ProtocolWhereClause) {
+    if (req.getKind() == RequirementReprKind::TypeConstraint ||
+        req.getKind() == RequirementReprKind::LayoutConstraint) {
+      if (auto *subjectTyR = req.getSubjectLoc().getTypeRepr()) {
+        if (auto *componentTyR = dyn_cast<ComponentIdentTypeRepr>(subjectTyR)) {
+          if (componentTyR->getIdentifier() == Context.Id_Self) {
+            diagnose(req.getSubjectLoc().getLoc(),
+                     diag::protocol_where_clause_self_requirement);
+
+            req.getSubjectLoc().setType(ErrorType::get(Context));
+
+            if (req.getKind() == RequirementReprKind::TypeConstraint)
+              req.getConstraintLoc().setType(ErrorType::get(Context));
+
+            req.setInvalid();
+            return true;
+          }
+        }
+      }
+    }
+  }
+
   switch (req.getKind()) {
   case RequirementReprKind::TypeConstraint: {
     // Validate the types.

lib/Sema/TypeChecker.h

@@ -552,6 +552,9 @@ enum class TypeResolutionFlags : unsigned {
 
   /// Whether we are in a requirement of a generic declaration
   GenericRequirement = 1 << 26,
+
+  /// Whether we are in a protocol's where clause
+  ProtocolWhereClause = 1 << 27,
 };
 
 /// Option set describing how type resolution should work.

test/IDE/print_ast_tc_decls.swift

@@ -1352,11 +1352,11 @@ extension ProtocolToExtend where Self.Assoc == Int {}
 
 // Protocol with where clauses
 
-protocol ProtocolWithWhereClause : QuxProtocol where Qux == Int, Self : FooProtocol {}
-// PREFER_TYPE_REPR_PRINTING: protocol ProtocolWithWhereClause : FooProtocol, QuxProtocol where Self.Qux == Int {
+protocol ProtocolWithWhereClause : QuxProtocol where Qux == Int {}
+// PREFER_TYPE_REPR_PRINTING: protocol ProtocolWithWhereClause : QuxProtocol where Self.Qux == Int {
 
-protocol ProtocolWithWhereClauseAndAssoc : QuxProtocol where Qux == Int, Self : FooProtocol {
-// PREFER_TYPE_REPR_PRINTING-DAG: protocol ProtocolWithWhereClauseAndAssoc : FooProtocol, QuxProtocol where Self.Qux == Int {
+protocol ProtocolWithWhereClauseAndAssoc : QuxProtocol where Qux == Int {
+// PREFER_TYPE_REPR_PRINTING-DAG: protocol ProtocolWithWhereClauseAndAssoc : QuxProtocol where Self.Qux == Int {
   associatedtype A1 : QuxProtocol where A1 : FooProtocol, A1.Qux : QuxProtocol, Int == A1.Qux.Qux
 // PREFER_TYPE_REPR_PRINTING-DAG: {{^}}  associatedtype A1 : FooProtocol, QuxProtocol where Self.A1.Qux : QuxProtocol, Self.A1.Qux.Qux == Int{{$}}