AST: Remove TypeBase::isEmptyExistentialComposition()

This is made redundant by TypeBase::isAny().

Author: slavapestov

include/swift/AST/Types.h

@@ -916,9 +916,6 @@ class alignas(1 << TypeAlignInBits) TypeBase {
 
   /// Whether this is the AnyObject type.
   bool isAnyObject();
-  
-  /// Whether this is an empty existential composition ("{}").
-  bool isEmptyExistentialComposition();
 
   /// Whether this is an existential composition containing
   /// Error.

lib/AST/Type.cpp

@@ -659,17 +659,6 @@ bool TypeBase::isAnyObject() {
   return false;
 }
 
-bool TypeBase::isEmptyExistentialComposition() {
-  if (auto emtType = ExistentialMetatypeType::get(this)) {
-    if (auto pcType = emtType->getInstanceType()->
-        getAs<ProtocolCompositionType>()) {
-      return pcType->getProtocols().empty();
-    }
-  }
-  
-  return false;
-}
-
 bool TypeBase::isExistentialWithError() {
   // FIXME: Compute this as a bit in TypeBase so this operation isn't
   // overly expensive.

lib/Sema/CSRanking.cpp

@@ -392,7 +392,7 @@ static bool hasEmptyExistentialParameterMismatch(ValueDecl *decl1,
       return false;
 
     if (t2->isAnyExistentialType() && !t1->isAnyExistentialType())
-      return t2->isEmptyExistentialComposition();
+      return t2->isAny();
   }
   return false;
 }

lib/Sema/CSSimplify.cpp

@@ -646,7 +646,7 @@ matchCallArguments(ConstraintSystem &cs, ConstraintKind kind,
 
   // In the empty existential parameter case,
   // it's sufficient to simply match call arguments.
-  if (paramType->isEmptyExistentialComposition()) {
+  if (paramType->isAny()) {
     // Argument of the existential type can't be inout.
     if (argType->is<InOutType>())
       return ConstraintSystem::SolutionKind::Error;
@@ -1124,7 +1124,7 @@ ConstraintSystem::matchExistentialTypes(Type type1, Type type2,
     return SolutionKind::Error;
 
   // Conformance to 'Any' always holds.
-  if (type2->isEmptyExistentialComposition())
+  if (type2->isAny())
     return SolutionKind::Solved;
 
   // If the first type is a type variable or member thereof, there's nothing
@@ -1326,7 +1326,7 @@ ConstraintSystem::matchTypes(Type type1, Type type2, ConstraintKind kind,
 
         // For symmetry with overload resolution, penalize conversions to empty
         // existentials.
-        if (type2->isEmptyExistentialComposition())
+        if (type2->isAny())
           increaseScore(ScoreKind::SK_EmptyExistentialConversion);
 
         return SolutionKind::Solved;