AST: Fix protocol composition canonicalization for primitive AnyObject

We were neglecting to take a primitive AnyObject member into
account. Also, canonicalize 'SomeClass & SomeProto & AnyObject'
down to 'SomeClass & SomeProto'.

Author: slavapestov

lib/AST/Type.cpp

@@ -889,16 +889,20 @@ Type TypeBase::getRValueInstanceType() {
 
 /// \brief Collect the protocols in the existential type T into the given
 /// vector.
-static void addProtocols(Type T, SmallVectorImpl<ProtocolDecl *> &Protocols,
-                         Type &Superclass) {
+static void addProtocols(Type T,
+                         SmallVectorImpl<ProtocolDecl *> &Protocols,
+                         Type &Superclass,
+                         bool &HasExplicitAnyObject) {
   if (auto Proto = T->getAs<ProtocolType>()) {
     Protocols.push_back(Proto->getDecl());
     return;
   }
 
   if (auto PC = T->getAs<ProtocolCompositionType>()) {
+    if (PC->hasExplicitAnyObject())
+      HasExplicitAnyObject = true;
     for (auto P : PC->getMembers())
-      addProtocols(P, Protocols, Superclass);
+      addProtocols(P, Protocols, Superclass, HasExplicitAnyObject);
     return;
   }
 
@@ -2780,12 +2784,16 @@ Type ProtocolCompositionType::get(const ASTContext &C,
   Type Superclass;
   SmallVector<ProtocolDecl *, 4> Protocols;
   for (Type t : Members) {
-    addProtocols(t, Protocols, Superclass);
+    addProtocols(t, Protocols, Superclass, HasExplicitAnyObject);
   }
 
   // Minimize the set of protocols composed together.
   ProtocolType::canonicalizeProtocols(Protocols);
 
+  // The presence of a superclass constraint makes AnyObject redundant.
+  if (Superclass)
+    HasExplicitAnyObject = false;
+
   // If one protocol remains with no further constraints, its nominal
   // type is the canonical type.
   if (Protocols.size() == 1 && !Superclass && !HasExplicitAnyObject)
@@ -2803,8 +2811,7 @@ Type ProtocolCompositionType::get(const ASTContext &C,
                  });
 
   // TODO: Canonicalize away HasExplicitAnyObject if it is implied
-  // by one of our member protocols or the presence of a superclass
-  // constraint.
+  // by one of our member protocols.
   return build(C, CanTypes, HasExplicitAnyObject);
 }