diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -463,6 +463,7 @@
   bool isInAnonymousNamespace() const;
 
   bool isInStdNamespace() const;
+  bool isInNamespace(llvm::StringRef Namespace) const;
 
   ASTContext &getASTContext() const LLVM_READONLY;
 
@@ -1945,6 +1946,8 @@
 
   bool isStdNamespace() const;
 
+  bool isNamespace(llvm::StringRef Namespace) const;
+
   bool isInlineNamespace() const;
 
   /// Determines whether this context is dependent on a
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -391,9 +391,11 @@
   return false;
 }
 
-bool Decl::isInStdNamespace() const {
+bool Decl::isInStdNamespace() const { return isInNamespace("std"); }
+
+bool Decl::isInNamespace(llvm::StringRef Namespace) const {
   const DeclContext *DC = getDeclContext();
-  return DC && DC->isStdNamespace();
+  return DC && DC->isNamespace(Namespace);
 }
 
 TranslationUnitDecl *Decl::getTranslationUnitDecl() {
@@ -1123,7 +1125,9 @@
          cast<NamespaceDecl>(this)->isInline();
 }
 
-bool DeclContext::isStdNamespace() const {
+bool DeclContext::isStdNamespace() const { return isNamespace("std"); }
+
+bool DeclContext::isNamespace(llvm::StringRef Namespace) const {
   if (!isNamespace())
     return false;
 
@@ -1136,7 +1140,7 @@
     return false;
 
   const IdentifierInfo *II = ND->getIdentifier();
-  return II && II->isStr("std");
+  return II && II->isStr(Namespace);
 }
 
 bool DeclContext::isDependentContext() const {