Index: lib/AST/ASTImporter.cpp
===================================================================
--- lib/AST/ASTImporter.cpp
+++ lib/AST/ASTImporter.cpp
@@ -438,6 +438,8 @@
 
     Error ImportTemplateInformation(FunctionDecl *FromFD, FunctionDecl *ToFD);
 
+    Error ImportFunctionDeclBody(FunctionDecl *FromFD, FunctionDecl *ToFD);
+
     bool IsStructuralMatch(Decl *From, Decl *To, bool Complain);
     bool IsStructuralMatch(RecordDecl *FromRecord, RecordDecl *ToRecord,
                            bool Complain = true);
@@ -2945,6 +2947,17 @@
   return FoundSpec;
 }
 
+Error ASTNodeImporter::ImportFunctionDeclBody(FunctionDecl *FromFD,
+                                              FunctionDecl *ToFD) {
+  if (Stmt *FromBody = FromFD->getBody()) {
+    if (ExpectedStmt ToBodyOrErr = import(FromBody))
+      ToFD->setBody(*ToBodyOrErr);
+    else
+      return ToBodyOrErr.takeError();
+  }
+  return Error::success();
+}
+
 ExpectedDecl ASTNodeImporter::VisitFunctionDecl(FunctionDecl *D) {
 
   SmallVector<Decl *, 2> Redecls = getCanonicalForwardRedeclChain(D);
@@ -2968,7 +2981,7 @@
   if (ToD)
     return ToD;
 
-  const FunctionDecl *FoundByLookup = nullptr;
+  FunctionDecl *FoundByLookup = nullptr;
   FunctionTemplateDecl *FromFT = D->getDescribedFunctionTemplate();
 
   // If this is a function template specialization, then try to find the same
@@ -3039,6 +3052,19 @@
     }
   }
 
+  if (FoundByLookup) {
+    if (auto *MD = dyn_cast<CXXMethodDecl>(FoundByLookup)) {
+      if (D->getLexicalDeclContext() == D->getDeclContext()) {
+        if (!D->doesThisDeclarationHaveABody())
+          return Importer.MapImported(D, FoundByLookup);
+        else {
+          // Let's continue and build up the redecl chain in this case.
+          // FIXME Merge the functions into one decl.
+        }
+      }
+    }
+  }
+
   DeclarationNameInfo NameInfo(Name, Loc);
   // Import additional name location/type info.
   if (Error Err = ImportDeclarationNameLoc(D->getNameInfo(), NameInfo))
@@ -3184,12 +3210,10 @@
   }
 
   if (D->doesThisDeclarationHaveABody()) {
-    if (Stmt *FromBody = D->getBody()) {
-      if (ExpectedStmt ToBodyOrErr = import(FromBody))
-        ToFunction->setBody(*ToBodyOrErr);
-      else
-        return ToBodyOrErr.takeError();
-    }
+    Error Err = ImportFunctionDeclBody(D, ToFunction);
+
+    if (Err)
+      return std::move(Err);
   }
 
   // FIXME: Other bits to merge?
Index: test/Analysis/Inputs/ctu-other.cpp
===================================================================
--- test/Analysis/Inputs/ctu-other.cpp
+++ test/Analysis/Inputs/ctu-other.cpp
@@ -24,33 +24,38 @@
 int fens(int x) {
   return x - 3;
 }
-}
+} // namespace embed_ns
 
 class embed_cls {
 public:
-  int fecl(int x) {
-    return x - 7;
-  }
+  int fecl(int x);
 };
+int embed_cls::fecl(int x) {
+  return x - 7;
 }
+} // namespace myns
 
 class mycls {
 public:
-  int fcl(int x) {
-    return x + 5;
-  }
-  static int fscl(int x) {
-    return x + 6;
-  }
+  int fcl(int x);
+  static int fscl(int x);
 
   class embed_cls2 {
   public:
-    int fecl2(int x) {
-      return x - 11;
-    }
+    int fecl2(int x);
   };
 };
 
+int mycls::fcl(int x) {
+  return x + 5;
+}
+int mycls::fscl(int x) {
+  return x + 6;
+}
+int mycls::embed_cls2::fecl2(int x) {
+  return x - 11;
+}
+
 namespace chns {
 int chf2(int x);
 
Index: test/Analysis/ctu-main.cpp
===================================================================
--- test/Analysis/ctu-main.cpp
+++ test/Analysis/ctu-main.cpp
@@ -78,6 +78,6 @@
   clang_analyzer_eval(fun_using_anon_struct(8) == 8); // expected-warning{{TRUE}}
 
   clang_analyzer_eval(other_macro_diag(1) == 1); // expected-warning{{TRUE}}
-  // expected-warning@Inputs/ctu-other.cpp:75{{REACHABLE}}
+  // expected-warning@Inputs/ctu-other.cpp:80{{REACHABLE}}
   MACRODIAG(); // expected-warning{{REACHABLE}}
 }
Index: unittests/AST/ASTImporterTest.cpp
===================================================================
--- unittests/AST/ASTImporterTest.cpp
+++ unittests/AST/ASTImporterTest.cpp
@@ -2233,6 +2233,191 @@
             }).match(ToTU, functionDecl()));
 }
 
+TEST_P(ImportFunctions, ImportOverriddenMethodTwice) {
+  auto Code =
+      R"(
+      struct B { virtual void f(); };
+      struct D:B { void f(); };
+      )";
+  auto BFP =
+      cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("B"))));
+  auto DFP =
+      cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("D"))));
+
+  Decl *FromTU0 = getTuDecl(Code, Lang_CXX);
+  auto *DF = FirstDeclMatcher<CXXMethodDecl>().match(FromTU0, DFP);
+  Import(DF, Lang_CXX);
+
+  Decl *FromTU1 = getTuDecl(Code, Lang_CXX, "input1.cc");
+  auto *BF = FirstDeclMatcher<CXXMethodDecl>().match(FromTU1, BFP);
+  Import(BF, Lang_CXX);
+
+  auto *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, BFP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, DFP), 1u);
+}
+
+TEST_P(ImportFunctions, ImportOverriddenMethodTwiceDefinitionFirst) {
+  auto CodeWithoutDef =
+      R"(
+      struct B { virtual void f(); };
+      struct D:B { void f(); };
+      )";
+  auto CodeWithDef =
+      R"(
+    struct B { virtual void f(){}; };
+    struct D:B { void f(){}; };
+  )";
+  auto BFP =
+      cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("B"))));
+  auto DFP =
+      cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("D"))));
+  auto BFDefP = cxxMethodDecl(
+      hasName("f"), hasParent(cxxRecordDecl(hasName("B"))), isDefinition());
+  auto DFDefP = cxxMethodDecl(
+      hasName("f"), hasParent(cxxRecordDecl(hasName("D"))), isDefinition());
+  auto FDefAllP = cxxMethodDecl(hasName("f"), isDefinition());
+
+  {
+    Decl *FromTU = getTuDecl(CodeWithDef, Lang_CXX, "input0.cc");
+    auto *FromD = FirstDeclMatcher<CXXMethodDecl>().match(FromTU, DFP);
+    Import(FromD, Lang_CXX);
+  }
+  {
+    Decl *FromTU = getTuDecl(CodeWithoutDef, Lang_CXX, "input1.cc");
+    auto *FromB = FirstDeclMatcher<CXXMethodDecl>().match(FromTU, BFP);
+    Import(FromB, Lang_CXX);
+  }
+
+  auto *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, BFP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, DFP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, BFDefP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, DFDefP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, FDefAllP), 2u);
+}
+
+TEST_P(ImportFunctions, ImportOverriddenMethodTwiceOutOfClassDef) {
+  auto Code =
+      R"(
+      struct B { virtual void f(); };
+      struct D:B { void f(); };
+      void B::f(){};
+      )";
+
+  auto BFP =
+      cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("B"))));
+  auto BFPIsDefP = cxxMethodDecl(
+      hasName("f"), hasParent(cxxRecordDecl(hasName("B"))), isDefinition());
+  auto DFP = cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("D"))),
+                           unless(isDefinition()));
+
+  Decl *FromTU0 = getTuDecl(Code, Lang_CXX);
+  auto *D = FirstDeclMatcher<CXXMethodDecl>().match(FromTU0, DFP);
+  Import(D, Lang_CXX);
+
+  Decl *FromTU1 = getTuDecl(Code, Lang_CXX, "input1.cc");
+  auto *B = FirstDeclMatcher<CXXMethodDecl>().match(FromTU1, BFP);
+  Import(B, Lang_CXX);
+
+  auto *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, BFP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, BFPIsDefP), 0u);
+
+  auto *ToB = FirstDeclMatcher<CXXRecordDecl>().match(
+      ToTU, cxxRecordDecl(hasName("B")));
+  auto *ToBFInClass = FirstDeclMatcher<CXXMethodDecl>().match(ToTU, BFP);
+  auto *ToBFOutOfClass = FirstDeclMatcher<CXXMethodDecl>().match(
+      ToTU, cxxMethodDecl(hasName("f"), isDefinition()));
+
+  // The definition should be out-of-class.
+  EXPECT_NE(ToBFInClass, ToBFOutOfClass);
+  EXPECT_NE(ToBFInClass->getLexicalDeclContext(),
+            ToBFOutOfClass->getLexicalDeclContext());
+  EXPECT_EQ(ToBFOutOfClass->getDeclContext(), ToB);
+  EXPECT_EQ(ToBFOutOfClass->getLexicalDeclContext(), ToTU);
+
+  // Check that the redecl chain is intact.
+  EXPECT_EQ(ToBFOutOfClass->getPreviousDecl(), ToBFInClass);
+}
+
+TEST_P(ImportFunctions,
+       ImportOverriddenMethodTwiceOutOfClassDefInSeparateCode) {
+  auto CodeTU0 =
+      R"(
+      struct B { virtual void f(); };
+      struct D:B { void f(); };
+      )";
+  auto CodeTU1 =
+      R"(
+      struct B { virtual void f(); };
+      struct D:B { void f(); };
+      void B::f(){}
+      void D::f(){}
+      void foo(B &b, D &d) { b.f(); d.f(); }
+      )";
+
+  auto BFP =
+      cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("B"))));
+  auto BFPIsDefP = cxxMethodDecl(
+      hasName("f"), hasParent(cxxRecordDecl(hasName("B"))), isDefinition());
+  auto DFP =
+      cxxMethodDecl(hasName("f"), hasParent(cxxRecordDecl(hasName("D"))));
+  auto DFPIsDefP = cxxMethodDecl(
+      hasName("f"), hasParent(cxxRecordDecl(hasName("D"))), isDefinition());
+  auto FooDef = functionDecl(hasName("foo"));
+
+  {
+    Decl *FromTU0 = getTuDecl(CodeTU0, Lang_CXX, "input0.cc");
+    auto *D = FirstDeclMatcher<CXXMethodDecl>().match(FromTU0, DFP);
+    Import(D, Lang_CXX);
+  }
+
+  {
+    Decl *FromTU1 = getTuDecl(CodeTU1, Lang_CXX, "input1.cc");
+    auto *Foo = FirstDeclMatcher<FunctionDecl>().match(FromTU1, FooDef);
+    Import(Foo, Lang_CXX);
+  }
+
+  auto *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, BFP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, DFP), 1u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, BFPIsDefP), 0u);
+  EXPECT_EQ(DeclCounter<FunctionDecl>().match(ToTU, DFPIsDefP), 0u);
+
+  auto *ToB = FirstDeclMatcher<CXXRecordDecl>().match(
+      ToTU, cxxRecordDecl(hasName("B")));
+  auto *ToD = FirstDeclMatcher<CXXRecordDecl>().match(
+      ToTU, cxxRecordDecl(hasName("D")));
+  auto *ToBFInClass = FirstDeclMatcher<CXXMethodDecl>().match(ToTU, BFP);
+  auto *ToBFOutOfClass = FirstDeclMatcher<CXXMethodDecl>().match(
+      ToTU, cxxMethodDecl(hasName("f"), isDefinition()));
+  auto *ToDFInClass = FirstDeclMatcher<CXXMethodDecl>().match(ToTU, DFP);
+  auto *ToDFOutOfClass = LastDeclMatcher<CXXMethodDecl>().match(
+      ToTU, cxxMethodDecl(hasName("f"), isDefinition()));
+
+  // The definition should be out-of-class.
+  EXPECT_NE(ToBFInClass, ToBFOutOfClass);
+  EXPECT_NE(ToBFInClass->getLexicalDeclContext(),
+            ToBFOutOfClass->getLexicalDeclContext());
+  EXPECT_EQ(ToBFOutOfClass->getDeclContext(), ToB);
+  EXPECT_EQ(ToBFOutOfClass->getLexicalDeclContext(), ToTU);
+
+  EXPECT_NE(ToDFInClass, ToDFOutOfClass);
+  EXPECT_NE(ToDFInClass->getLexicalDeclContext(),
+            ToDFOutOfClass->getLexicalDeclContext());
+  EXPECT_EQ(ToDFOutOfClass->getDeclContext(), ToD);
+  EXPECT_EQ(ToDFOutOfClass->getLexicalDeclContext(), ToTU);
+
+  // Check that the redecl chain is intact.
+  EXPECT_EQ(ToBFOutOfClass->getPreviousDecl(), ToBFInClass);
+  EXPECT_EQ(ToDFOutOfClass->getPreviousDecl(), ToDFInClass);
+}
+
 struct ImportFriendFunctions : ImportFunctions {};
 
 TEST_P(ImportFriendFunctions, ImportFriendFunctionRedeclChainProto) {