Index: cfe/trunk/lib/AST/ASTImporter.cpp
===================================================================
--- cfe/trunk/lib/AST/ASTImporter.cpp
+++ cfe/trunk/lib/AST/ASTImporter.cpp
@@ -2633,7 +2633,7 @@
 
   // We may already have a record of the same name; try to find and match it.
   RecordDecl *PrevDecl = nullptr;
-  if (!DC->isFunctionOrMethod()) {
+  if (!DC->isFunctionOrMethod() && !D->isLambda()) {
     SmallVector<NamedDecl *, 4> ConflictingDecls;
     auto FoundDecls =
         Importer.findDeclsInToCtx(DC, SearchName);
Index: cfe/trunk/unittests/AST/ASTImporterTest.cpp
===================================================================
--- cfe/trunk/unittests/AST/ASTImporterTest.cpp
+++ cfe/trunk/unittests/AST/ASTImporterTest.cpp
@@ -5644,6 +5644,117 @@
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, CanonicalRedeclChain,
                         ::testing::Values(ArgVector()), );
 
+TEST_P(ASTImporterOptionSpecificTestBase, LambdasAreDifferentiated) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      void f() {
+        auto L0 = [](){};
+        auto L1 = [](){};
+      }
+      )",
+      Lang_CXX11, "input0.cc");
+  auto Pattern = lambdaExpr();
+  CXXRecordDecl *FromL0 =
+      FirstDeclMatcher<LambdaExpr>().match(FromTU, Pattern)->getLambdaClass();
+  CXXRecordDecl *FromL1 =
+      LastDeclMatcher<LambdaExpr>().match(FromTU, Pattern)->getLambdaClass();
+  ASSERT_NE(FromL0, FromL1);
+
+  CXXRecordDecl *ToL0 = Import(FromL0, Lang_CXX11);
+  CXXRecordDecl *ToL1 = Import(FromL1, Lang_CXX11);
+  EXPECT_NE(ToL0, ToL1);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase,
+       LambdasInFunctionParamsAreDifferentiated) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      template <typename F0, typename F1>
+      void f(F0 L0 = [](){}, F1 L1 = [](){}) {}
+      )",
+      Lang_CXX11, "input0.cc");
+  auto Pattern = cxxRecordDecl(isLambda());
+  CXXRecordDecl *FromL0 =
+      FirstDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  CXXRecordDecl *FromL1 =
+      LastDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  ASSERT_NE(FromL0, FromL1);
+
+  CXXRecordDecl *ToL0 = Import(FromL0, Lang_CXX11);
+  CXXRecordDecl *ToL1 = Import(FromL1, Lang_CXX11);
+  ASSERT_NE(ToL0, ToL1);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase,
+       LambdasInFunctionParamsAreDifferentiatedWhenMacroIsUsed) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      #define LAMBDA [](){}
+      template <typename F0, typename F1>
+      void f(F0 L0 = LAMBDA, F1 L1 = LAMBDA) {}
+      )",
+      Lang_CXX11, "input0.cc");
+  auto Pattern = cxxRecordDecl(isLambda());
+  CXXRecordDecl *FromL0 =
+      FirstDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  CXXRecordDecl *FromL1 =
+      LastDeclMatcher<CXXRecordDecl>().match(FromTU, Pattern);
+  ASSERT_NE(FromL0, FromL1);
+
+  Import(FromL0, Lang_CXX11);
+  Import(FromL1, Lang_CXX11);
+  CXXRecordDecl *ToL0 = Import(FromL0, Lang_CXX11);
+  CXXRecordDecl *ToL1 = Import(FromL1, Lang_CXX11);
+  ASSERT_NE(ToL0, ToL1);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportAssignedLambda) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      void f() {
+        auto x = []{} = {}; auto x2 = x;
+      }
+      )",
+      Lang_CXX2a, "input0.cc");
+  auto FromF = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("f")));
+  // We have only one lambda class.
+  ASSERT_EQ(
+      DeclCounter<CXXRecordDecl>().match(FromTU, cxxRecordDecl(isLambda())),
+      1u);
+
+  FunctionDecl *ToF = Import(FromF, Lang_CXX2a);
+  EXPECT_TRUE(ToF);
+  TranslationUnitDecl *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+  // We have only one lambda class after the import.
+  EXPECT_EQ(DeclCounter<CXXRecordDecl>().match(ToTU, cxxRecordDecl(isLambda())),
+            1u);
+}
+
+TEST_P(ASTImporterOptionSpecificTestBase, ImportDefaultConstructibleLambdas) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      void f() {
+        auto x = []{} = {};
+        auto xb = []{} = {};
+      }
+      )",
+      Lang_CXX2a, "input0.cc");
+  auto FromF = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("f")));
+  // We have two lambda classes.
+  ASSERT_EQ(
+      DeclCounter<CXXRecordDecl>().match(FromTU, cxxRecordDecl(isLambda())),
+      2u);
+
+  FunctionDecl *ToF = Import(FromF, Lang_CXX2a);
+  EXPECT_TRUE(ToF);
+  TranslationUnitDecl *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+  // We have two lambda classes after the import.
+  EXPECT_EQ(DeclCounter<CXXRecordDecl>().match(ToTU, cxxRecordDecl(isLambda())),
+            2u);
+}
+
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, ASTImporterLookupTableTest,
                         DefaultTestValuesForRunOptions, );