diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
index 8715067ce659..ecb879417438 100644
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -3273,6 +3273,16 @@ void Redeclarable<decl_type>::setPreviousDeclaration(decl_type *PrevDecl) {
     ND->ClearLinkageCache();
 }
 
+// Inline function definitions.
+
+/// \brief Check if the given decl is complete.
+///
+/// We use this function to break a cycle between the inline definitions in
+/// Type.h and Decl.h.
+inline bool IsEnumDeclComplete(EnumDecl *ED) {
+  return ED->isComplete();
+}
+
 }  // end namespace clang
 
 #endif
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index 8146d7b6f116..1b00594d6bdb 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -4816,6 +4816,55 @@ inline bool Type::isNonOverloadPlaceholderType() const {
   return false;
 }
 
+inline bool Type::isHalfType() const {
+  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
+    return BT->getKind() == BuiltinType::Half;
+  // FIXME: Should we allow complex __fp16? Probably not.
+  return false;
+}
+
+inline bool Type::isNullPtrType() const {
+  if (const BuiltinType *BT = getAs<BuiltinType>())
+    return BT->getKind() == BuiltinType::NullPtr;
+  return false;
+}
+
+extern bool IsEnumDeclComplete(EnumDecl *);
+
+inline bool Type::isScalarType() const {
+  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
+    return BT->getKind() > BuiltinType::Void &&
+           BT->getKind() <= BuiltinType::NullPtr;
+  if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
+    // Enums are scalar types, but only if they are defined.  Incomplete enums
+    // are not treated as scalar types.
+    return IsEnumDeclComplete(ET->getDecl());
+  return isa<PointerType>(CanonicalType) ||
+         isa<BlockPointerType>(CanonicalType) ||
+         isa<MemberPointerType>(CanonicalType) ||
+         isa<ComplexType>(CanonicalType) ||
+         isa<ObjCObjectPointerType>(CanonicalType);
+}
+
+inline bool Type::isIntegralOrEnumerationType() const {
+  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
+    return BT->getKind() >= BuiltinType::Bool &&
+           BT->getKind() <= BuiltinType::Int128;
+
+  // Check for a complete enum type; incomplete enum types are not properly an
+  // enumeration type in the sense required here.
+  if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
+    return IsEnumDeclComplete(ET->getDecl());
+
+  return false;  
+}
+
+inline bool Type::isBooleanType() const {
+  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
+    return BT->getKind() == BuiltinType::Bool;
+  return false;
+}
+
 /// \brief Determines whether this is a type for which one can define
 /// an overloaded operator.
 inline bool Type::isOverloadableType() const {
diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index c58debbbd27b..ce805617f89d 100644
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -556,17 +556,6 @@ AutoType *Type::getContainedAutoType() const {
   return GetContainedAutoVisitor().Visit(this);
 }
 
-bool Type::isIntegerType() const {
-  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
-    return BT->getKind() >= BuiltinType::Bool &&
-           BT->getKind() <= BuiltinType::Int128;
-  if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
-    // Incomplete enum types are not treated as integer types.
-    // FIXME: In C++, enum types are never integer types.
-    return ET->getDecl()->isComplete() && !ET->getDecl()->isScoped();
-  return false;
-}
-
 bool Type::hasIntegerRepresentation() const {
   if (const VectorType *VT = dyn_cast<VectorType>(CanonicalType))
     return VT->getElementType()->isIntegerType();
@@ -605,18 +594,6 @@ bool Type::isIntegralType(ASTContext &Ctx) const {
   return false;
 }
 
-bool Type::isIntegralOrEnumerationType() const {
-  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
-    return BT->getKind() >= BuiltinType::Bool &&
-           BT->getKind() <= BuiltinType::Int128;
-
-  // Check for a complete enum type; incomplete enum types are not properly an
-  // enumeration type in the sense required here.
-  if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
-    return ET->getDecl()->isComplete();
-
-  return false;  
-}
 
 bool Type::isIntegralOrUnscopedEnumerationType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
@@ -634,9 +611,15 @@ bool Type::isIntegralOrUnscopedEnumerationType() const {
 }
 
 
-bool Type::isBooleanType() const {
+
+bool Type::isIntegerType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
-    return BT->getKind() == BuiltinType::Bool;
+    return BT->getKind() >= BuiltinType::Bool &&
+           BT->getKind() <= BuiltinType::Int128;
+  if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
+    // Incomplete enum types are not treated as integer types.
+    // FIXME: In C++, enum types are never integer types.
+    return ET->getDecl()->isComplete() && !ET->getDecl()->isScoped();
   return false;
 }
 
@@ -767,13 +750,6 @@ bool Type::hasUnsignedIntegerRepresentation() const {
     return isUnsignedIntegerType();
 }
 
-bool Type::isHalfType() const {
-  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
-    return BT->getKind() == BuiltinType::Half;
-  // FIXME: Should we allow complex __fp16? Probably not.
-  return false;
-}
-
 bool Type::isFloatingType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() >= BuiltinType::Half &&
@@ -820,21 +796,6 @@ bool Type::isArithmeticType() const {
   return isa<ComplexType>(CanonicalType);
 }
 
-bool Type::isScalarType() const {
-  if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
-    return BT->getKind() > BuiltinType::Void &&
-           BT->getKind() <= BuiltinType::NullPtr;
-  if (const EnumType *ET = dyn_cast<EnumType>(CanonicalType))
-    // Enums are scalar types, but only if they are defined.  Incomplete enums
-    // are not treated as scalar types.
-    return ET->getDecl()->isComplete();
-  return isa<PointerType>(CanonicalType) ||
-         isa<BlockPointerType>(CanonicalType) ||
-         isa<MemberPointerType>(CanonicalType) ||
-         isa<ComplexType>(CanonicalType) ||
-         isa<ObjCObjectPointerType>(CanonicalType);
-}
-
 Type::ScalarTypeKind Type::getScalarTypeKind() const {
   assert(isScalarType());
 
@@ -1312,12 +1273,6 @@ bool Type::isPromotableIntegerType() const {
   return false;
 }
 
-bool Type::isNullPtrType() const {
-  if (const BuiltinType *BT = getAs<BuiltinType>())
-    return BT->getKind() == BuiltinType::NullPtr;
-  return false;
-}
-
 bool Type::isSpecifierType() const {
   // Note that this intentionally does not use the canonical type.
   switch (getTypeClass()) {