Index: include/clang/Tooling/Core/Lookup.h
===================================================================
--- include/clang/Tooling/Core/Lookup.h
+++ include/clang/Tooling/Core/Lookup.h
@@ -14,6 +14,7 @@
 #define LLVM_CLANG_TOOLING_CORE_LOOKUP_H
 
 #include "clang/Basic/LLVM.h"
+#include "clang/Basic/SourceLocation.h"
 #include <string>
 
 namespace clang {
@@ -30,6 +31,7 @@
 /// This does not perform a full C++ lookup so ADL will not work.
 ///
 /// \param Use The nested name to be replaced.
+/// \param UseLoc The location of name to be replaced.
 /// \param UseContext The context in which the nested name is contained. This
 ///                   will be used to minimize namespace qualifications.
 /// \param FromDecl The declaration to which the nested name points.
@@ -37,6 +39,7 @@
 ///                          qualified including a leading "::".
 /// \returns The new name to be inserted in place of the current nested name.
 std::string replaceNestedName(const NestedNameSpecifier *Use,
+                              SourceLocation UseLoc,
                               const DeclContext *UseContext,
                               const NamedDecl *FromDecl,
                               StringRef ReplacementString);
Index: lib/Tooling/Core/Lookup.cpp
===================================================================
--- lib/Tooling/Core/Lookup.cpp
+++ lib/Tooling/Core/Lookup.cpp
@@ -14,6 +14,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclarationName.h"
+#include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/SmallVector.h"
 using namespace clang;
 using namespace clang::tooling;
@@ -123,7 +124,8 @@
 // FIXME: consider using namespaces.
 static std::string disambiguateSpellingInScope(StringRef Spelling,
                                                StringRef QName,
-                                               const DeclContext &UseContext) {
+                                               const DeclContext &UseContext,
+                                               SourceLocation UseLoc) {
   assert(QName.startswith("::"));
   assert(QName.endswith(Spelling));
   if (Spelling.startswith("::"))
@@ -138,9 +140,10 @@
       getAllNamedNamespaces(&UseContext);
   auto &AST = UseContext.getParentASTContext();
   StringRef TrimmedQName = QName.substr(2);
+  const auto &SM = UseContext.getParentASTContext().getSourceManager();
+  UseLoc = SM.getSpellingLoc(UseLoc);
 
-  auto IsAmbiguousSpelling = [&EnclosingNamespaces, &AST, &TrimmedQName](
-                                 const llvm::StringRef CurSpelling) {
+  auto IsAmbiguousSpelling = [&](const llvm::StringRef CurSpelling) {
     if (CurSpelling.startswith("::"))
       return false;
     // Lookup the first component of Spelling in all enclosing namespaces
@@ -151,7 +154,13 @@
       auto LookupRes = NS->lookup(DeclarationName(&AST.Idents.get(Head)));
       if (!LookupRes.empty()) {
         for (const NamedDecl *Res : LookupRes)
-          if (!TrimmedQName.startswith(Res->getQualifiedNameAsString()))
+          // If `Res` is not visible in `UseLoc`, we don't consider it
+          // ambiguous. For example, a reference in a header file should not be
+          // affected by a potentially ambiguous name in some file that includes
+          // the header.
+          if (!TrimmedQName.startswith(Res->getQualifiedNameAsString()) &&
+              SM.isBeforeInTranslationUnit(
+                  SM.getSpellingLoc(Res->getLocation()), UseLoc))
             return true;
       }
     }
@@ -172,6 +181,7 @@
 }
 
 std::string tooling::replaceNestedName(const NestedNameSpecifier *Use,
+                                       SourceLocation UseLoc,
                                        const DeclContext *UseContext,
                                        const NamedDecl *FromDecl,
                                        StringRef ReplacementString) {
@@ -206,5 +216,6 @@
   StringRef Suggested = getBestNamespaceSubstr(UseContext, ReplacementString,
                                                isFullyQualified(Use));
 
-  return disambiguateSpellingInScope(Suggested, ReplacementString, *UseContext);
+  return disambiguateSpellingInScope(Suggested, ReplacementString, *UseContext,
+                                     UseLoc);
 }
Index: lib/Tooling/Refactoring/Rename/USRLocFinder.cpp
===================================================================
--- lib/Tooling/Refactoring/Rename/USRLocFinder.cpp
+++ lib/Tooling/Refactoring/Rename/USRLocFinder.cpp
@@ -542,8 +542,8 @@
         if (!llvm::isa<clang::TranslationUnitDecl>(
                 RenameInfo.Context->getDeclContext())) {
           ReplacedName = tooling::replaceNestedName(
-              RenameInfo.Specifier, RenameInfo.Context->getDeclContext(),
-              RenameInfo.FromDecl,
+              RenameInfo.Specifier, RenameInfo.Begin,
+              RenameInfo.Context->getDeclContext(), RenameInfo.FromDecl,
               NewName.startswith("::") ? NewName.str()
                                        : ("::" + NewName).str());
         } else {
Index: unittests/Tooling/LookupTest.cpp
===================================================================
--- unittests/Tooling/LookupTest.cpp
+++ unittests/Tooling/LookupTest.cpp
@@ -44,8 +44,8 @@
     const auto *Callee = cast<DeclRefExpr>(Expr->getCallee()->IgnoreImplicit());
     const ValueDecl *FD = Callee->getDecl();
     return tooling::replaceNestedName(
-        Callee->getQualifier(), Visitor.DeclStack.back()->getDeclContext(), FD,
-        ReplacementString);
+        Callee->getQualifier(), Callee->getLocation(),
+        Visitor.DeclStack.back()->getDeclContext(), FD, ReplacementString);
   };
 
   Visitor.OnCall = [&](CallExpr *Expr) {
@@ -181,12 +181,12 @@
 TEST(LookupTest, replaceNestedClassName) {
   GetDeclsVisitor Visitor;
 
-  auto replaceRecordTypeLoc = [&](RecordTypeLoc Loc,
+  auto replaceRecordTypeLoc = [&](RecordTypeLoc TLoc,
                                   StringRef ReplacementString) {
-    const auto *FD = cast<CXXRecordDecl>(Loc.getDecl());
+    const auto *FD = cast<CXXRecordDecl>(TLoc.getDecl());
     return tooling::replaceNestedName(
-        nullptr, Visitor.DeclStack.back()->getDeclContext(), FD,
-        ReplacementString);
+        nullptr, TLoc.getBeginLoc(), Visitor.DeclStack.back()->getDeclContext(),
+        FD, ReplacementString);
   };
 
   Visitor.OnRecordTypeLoc = [&](RecordTypeLoc Type) {
@@ -211,6 +211,40 @@
   };
   Visitor.runOver("namespace a { namespace b { class Foo {}; } }\n"
                   "namespace c { using a::b::Foo; Foo f();; }\n");
+
+  // Rename TypeLoc `x::y::Old` to new name `x::Foo` at [0] and check that the
+  // type is replaced with "Foo" instead of "x::Foo". Although there is a symbol
+  // `x::y::Foo` in c.cc [1], it should not make "Foo" at [0] ambiguous because
+  // it's not visible at [0].
+  Visitor.OnRecordTypeLoc = [&](RecordTypeLoc Type) {
+    if (Type.getDecl()->getQualifiedNameAsString() == "x::y::Old")
+      EXPECT_EQ("Foo", replaceRecordTypeLoc(Type, "::x::Foo"));
+  };
+  Visitor.runOver(R"(
+    // a.h
+    namespace x {
+     namespace y {
+      class Old {};
+      class Other {};
+     }
+    }
+
+    // b.h
+    namespace x {
+     namespace y {
+      // This is to be renamed to x::Foo
+      // The expected replacement is "Foo".
+      Old f;  // [0].
+     }
+    }
+
+    // c.cc
+    namespace x {
+    namespace y {
+     using Foo = ::x::y::Other; // [1]
+    }
+    }
+    )");
 }
 
 } // end anonymous namespace