Sema: Allow protocols with 'Self' constraints again

include/swift/AST/DeclContext.h

@@ -501,7 +501,7 @@ class alignas(1 << DeclContextAlignInBits) DeclContext {
   /// lookup.
   ///
   /// \returns true if anything was found.
-  bool lookupQualified(ArrayRef<TypeDecl *> types, DeclName member,
+  bool lookupQualified(ArrayRef<NominalTypeDecl *> types, DeclName member,
                        NLOptions options,
                        SmallVectorImpl<ValueDecl *> &decls) const;
 

include/swift/AST/NameLookup.h

@@ -34,6 +34,7 @@ namespace swift {
   class Type;
   class TypeDecl;
   class ValueDecl;
+  struct SelfBounds;
 
 /// LookupResultEntry - One result of unqualified lookup.
 struct LookupResultEntry {
@@ -374,6 +375,12 @@ getDirectlyInheritedNominalTypeDecls(
                       llvm::PointerUnion<TypeDecl *, ExtensionDecl *> decl,
                       bool &anyObject);
 
+/// Retrieve the set of nominal type declarations that appear as the
+/// constraint type of any "Self" constraints in the where clause of the
+/// given protocol or protocol extension.
+SelfBounds getSelfBoundsFromWhereClause(
+    llvm::PointerUnion<TypeDecl *, ExtensionDecl *> decl);
+
 } // end namespace swift
 
 #endif

include/swift/AST/NameLookupRequests.h

@@ -182,26 +182,31 @@ class ExtendedNominalRequest :
   void noteCycleStep(DiagnosticEngine &diags) const;
 };
 
+struct SelfBounds {
+  llvm::TinyPtrVector<NominalTypeDecl *> decls;
+  bool anyObject = false;
+};
+
 /// Request the nominal types that occur as the right-hand side of "Self: Foo"
 /// constraints in the "where" clause of a protocol extension.
 class SelfBoundsFromWhereClauseRequest :
     public SimpleRequest<SelfBoundsFromWhereClauseRequest,
                          CacheKind::Uncached,
-                         llvm::TinyPtrVector<NominalTypeDecl *>,
-                         ExtensionDecl *> {
+                         SelfBounds,
+                         llvm::PointerUnion<TypeDecl *, ExtensionDecl *>> {
 public:
   using SimpleRequest::SimpleRequest;
 
 private:
   friend SimpleRequest;
 
   // Evaluation.
-  llvm::TinyPtrVector<NominalTypeDecl *> evaluate(Evaluator &evaluator,
-                                                  ExtensionDecl *ext) const;
+  SelfBounds evaluate(Evaluator &evaluator,
+                      llvm::PointerUnion<TypeDecl *, ExtensionDecl *>) const;
 
 public:
   // Cycle handling
-  llvm::TinyPtrVector<NominalTypeDecl *> breakCycle() const { return { }; }
+  SelfBounds breakCycle() const { return { }; }
   void diagnoseCycle(DiagnosticEngine &diags) const;
   void noteCycleStep(DiagnosticEngine &diags) const;
 };

lib/AST/Decl.cpp

@@ -3642,7 +3642,7 @@ ProtocolDecl::getInheritedProtocols() const {
   SmallPtrSet<const ProtocolDecl *, 4> known;
   known.insert(this);
   bool anyObject = false;
-  for (const auto &found :
+  for (const auto found :
            getDirectlyInheritedNominalTypeDecls(
              const_cast<ProtocolDecl *>(this), anyObject)) {
     if (auto proto = dyn_cast<ProtocolDecl>(found.second)) {
@@ -3758,12 +3758,14 @@ bool ProtocolDecl::requiresClassSlow() {
     getDirectlyInheritedNominalTypeDecls(this, anyObject);
 
   // Quick check: do we inherit AnyObject?
-  if (anyObject)
-    return Bits.ProtocolDecl.RequiresClass = true;
+  if (anyObject) {
+    Bits.ProtocolDecl.RequiresClass = true;
+    return true;
+  }
 
   // Look through all of the inherited nominals for a superclass or a
   // class-bound protocol.
-  for (const auto &found : allInheritedNominals) {
+  for (const auto found : allInheritedNominals) {
     // Superclass bound.
     if (isa<ClassDecl>(found.second))
       return Bits.ProtocolDecl.RequiresClass = true;

lib/AST/GenericSignatureBuilder.cpp

@@ -7251,19 +7251,18 @@ void GenericSignatureBuilder::enumerateRequirements(
     // Enumerate conformance requirements.
     SmallVector<ProtocolDecl *, 4> protocols;
     DenseMap<ProtocolDecl *, const RequirementSource *> protocolSources;
-    if (equivClass) {
-      for (const auto &conforms : equivClass->conformsTo) {
-        protocols.push_back(conforms.first);
-        assert(protocolSources.count(conforms.first) == 0 && 
-               "redundant protocol requirement?");
-
-        protocolSources.insert(
-          {conforms.first,
-           *getBestConstraintSource<ProtocolDecl *>(conforms.second,
-             [&](ProtocolDecl *proto) {
-               return proto == conforms.first;
-             })});
-      }
+
+    for (const auto &conforms : equivClass->conformsTo) {
+      protocols.push_back(conforms.first);
+      assert(protocolSources.count(conforms.first) == 0 &&
+             "redundant protocol requirement?");
+
+      protocolSources.insert(
+        {conforms.first,
+         *getBestConstraintSource<ProtocolDecl *>(conforms.second,
+           [&](ProtocolDecl *proto) {
+             return proto == conforms.first;
+           })});
     }
 
     // Sort the protocols in canonical order.