Index: cfe/trunk/lib/AST/ASTImporter.cpp
===================================================================
--- cfe/trunk/lib/AST/ASTImporter.cpp
+++ cfe/trunk/lib/AST/ASTImporter.cpp
@@ -57,6 +57,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Casting.h"
@@ -1631,16 +1632,32 @@
     auto ToDCOrErr = Importer.ImportContext(FromDC);
     return ToDCOrErr.takeError();
   }
+
+  // We use strict error handling in case of records and enums, but not
+  // with e.g. namespaces.
+  //
+  // FIXME Clients of the ASTImporter should be able to choose an
+  // appropriate error handling strategy for their needs.  For instance,
+  // they may not want to mark an entire namespace as erroneous merely
+  // because there is an ODR error with two typedefs.  As another example,
+  // the client may allow EnumConstantDecls with same names but with
+  // different values in two distinct translation units.
+  bool AccumulateChildErrors = isa<TagDecl>(FromDC);
+
+  Error ChildErrors = Error::success();
   llvm::SmallVector<Decl *, 8> ImportedDecls;
   for (auto *From : FromDC->decls()) {
     ExpectedDecl ImportedOrErr = import(From);
-    if (!ImportedOrErr)
-      // Ignore the error, continue with next Decl.
-      // FIXME: Handle this case somehow better.
-      consumeError(ImportedOrErr.takeError());
+    if (!ImportedOrErr) {
+      if (AccumulateChildErrors)
+        ChildErrors =
+            joinErrors(std::move(ChildErrors), ImportedOrErr.takeError());
+      else
+        consumeError(ImportedOrErr.takeError());
+    }
   }
 
-  return Error::success();
+  return ChildErrors;
 }
 
 Error ASTNodeImporter::ImportDeclContext(
@@ -1698,6 +1715,11 @@
   }
 
   To->startDefinition();
+  // Complete the definition even if error is returned.
+  // The RecordDecl may be already part of the AST so it is better to
+  // have it in complete state even if something is wrong with it.
+  auto DefinitionCompleter =
+      llvm::make_scope_exit([To]() { To->completeDefinition(); });
 
   if (Error Err = setTypedefNameForAnonDecl(From, To, Importer))
     return Err;
@@ -1822,7 +1844,6 @@
     if (Error Err = ImportDeclContext(From, /*ForceImport=*/true))
       return Err;
 
-  To->completeDefinition();
   return Error::success();
 }
 
Index: cfe/trunk/unittests/AST/ASTImporterTest.cpp
===================================================================
--- cfe/trunk/unittests/AST/ASTImporterTest.cpp
+++ cfe/trunk/unittests/AST/ASTImporterTest.cpp
@@ -4738,6 +4738,93 @@
   EXPECT_EQ(OptErr->Error, ImportError::UnsupportedConstruct);
 }
 
+// An error should be set for a class if we cannot import one member.
+TEST_P(ErrorHandlingTest, ErrorIsPropagatedFromMemberToClass) {
+  TranslationUnitDecl *FromTU = getTuDecl(
+      std::string(R"(
+      class X {
+        void f() { )") + ErroneousStmt + R"( } // This member has the error
+                                               // during import.
+        void ok();        // The error should not prevent importing this.
+      };                  // An error will be set for X too.
+      )",
+      Lang_CXX);
+  auto *FromX = FirstDeclMatcher<CXXRecordDecl>().match(
+      FromTU, cxxRecordDecl(hasName("X")));
+  CXXRecordDecl *ImportedX = Import(FromX, Lang_CXX);
+
+  // An error is set for X.
+  EXPECT_FALSE(ImportedX);
+  ASTImporter *Importer = findFromTU(FromX)->Importer.get();
+  Optional<ImportError> OptErr = Importer->getImportDeclErrorIfAny(FromX);
+  ASSERT_TRUE(OptErr);
+  EXPECT_EQ(OptErr->Error, ImportError::UnsupportedConstruct);
+
+  // An error is set for f().
+  auto *FromF = FirstDeclMatcher<CXXMethodDecl>().match(
+      FromTU, cxxMethodDecl(hasName("f")));
+  OptErr = Importer->getImportDeclErrorIfAny(FromF);
+  ASSERT_TRUE(OptErr);
+  EXPECT_EQ(OptErr->Error, ImportError::UnsupportedConstruct);
+  // And any subsequent import should fail.
+  CXXMethodDecl *ImportedF = Import(FromF, Lang_CXX);
+  EXPECT_FALSE(ImportedF);
+
+  // There is no error set for ok().
+  auto *FromOK = FirstDeclMatcher<CXXMethodDecl>().match(
+      FromTU, cxxMethodDecl(hasName("ok")));
+  OptErr = Importer->getImportDeclErrorIfAny(FromOK);
+  EXPECT_FALSE(OptErr);
+  // And we should be able to import.
+  CXXMethodDecl *ImportedOK = Import(FromOK, Lang_CXX);
+  EXPECT_TRUE(ImportedOK);
+
+  // Unwary clients may access X even if the error is set, so, at least make
+  // sure the class is set to be complete.
+  CXXRecordDecl *ToX = cast<CXXRecordDecl>(ImportedOK->getDeclContext());
+  EXPECT_TRUE(ToX->isCompleteDefinition());
+}
+
+TEST_P(ErrorHandlingTest, ErrorIsNotPropagatedFromMemberToNamespace) {
+  TranslationUnitDecl *FromTU = getTuDecl(
+      std::string(R"(
+      namespace X {
+        void f() { )") + ErroneousStmt + R"( } // This member has the error
+                                               // during import.
+        void ok();        // The error should not prevent importing this.
+      };                  // An error will be set for X too.
+      )",
+      Lang_CXX);
+  auto *FromX = FirstDeclMatcher<NamespaceDecl>().match(
+      FromTU, namespaceDecl(hasName("X")));
+  NamespaceDecl *ImportedX = Import(FromX, Lang_CXX);
+
+  // There is no error set for X.
+  EXPECT_TRUE(ImportedX);
+  ASTImporter *Importer = findFromTU(FromX)->Importer.get();
+  Optional<ImportError> OptErr = Importer->getImportDeclErrorIfAny(FromX);
+  ASSERT_FALSE(OptErr);
+
+  // An error is set for f().
+  auto *FromF = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("f")));
+  OptErr = Importer->getImportDeclErrorIfAny(FromF);
+  ASSERT_TRUE(OptErr);
+  EXPECT_EQ(OptErr->Error, ImportError::UnsupportedConstruct);
+  // And any subsequent import should fail.
+  FunctionDecl *ImportedF = Import(FromF, Lang_CXX);
+  EXPECT_FALSE(ImportedF);
+
+  // There is no error set for ok().
+  auto *FromOK = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("ok")));
+  OptErr = Importer->getImportDeclErrorIfAny(FromOK);
+  EXPECT_FALSE(OptErr);
+  // And we should be able to import.
+  FunctionDecl *ImportedOK = Import(FromOK, Lang_CXX);
+  EXPECT_TRUE(ImportedOK);
+}
+
 INSTANTIATE_TEST_CASE_P(ParameterizedTests, ErrorHandlingTest,
                         DefaultTestValuesForRunOptions, );