Index: unittests/AST/CMakeLists.txt
===================================================================
--- unittests/AST/CMakeLists.txt
+++ unittests/AST/CMakeLists.txt
@@ -15,6 +15,7 @@
   NamedDeclPrinterTest.cpp
   SourceLocationTest.cpp
   StmtPrinterTest.cpp
+  LeftoverExpressionsForODRAfterFatalError.cpp
   )
 
 target_link_libraries(ASTTests
Index: unittests/AST/LeftoverExpressionsForODRAfterFatalError.cpp
===================================================================
--- /dev/null
+++ unittests/AST/LeftoverExpressionsForODRAfterFatalError.cpp
@@ -0,0 +1,96 @@
+//===- unittests/AST/LeftoverExpressionsForODRAfterFatalError.cpp ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is the regression for the next assert after fatal error:
+// clang::Sema::ActOnFinishFunctionBody(clang::Decl*, clang::Stmt*, bool):
+// Assertion `MaybeODRUseExprs.empty() && "Leftover expressions for odr-use checking"' failed.
+//
+// After DiagnosticsEngine::{Reset(),setIgnoreAllWarnings()}, using ASTConsumer
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Tooling/Tooling.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "gtest/gtest.h"
+
+using namespace clang::ast_matchers;
+using namespace clang::tooling;
+
+namespace {
+
+using namespace clang;
+
+class TestConsumer : public ASTConsumer {
+public:
+    TestConsumer(clang::CompilerInstance &ci)
+        : clang::ASTConsumer()
+        , ci(ci) {}
+    virtual ~TestConsumer() {}
+
+    virtual bool HandleTopLevelDecl(clang::DeclGroupRef D) override {
+        if (ci.getDiagnostics().hasFatalErrorOccurred()) {
+            ci.getDiagnostics().Reset();
+            ci.getDiagnostics().setIgnoreAllWarnings(true);
+        }
+        return true;
+    }
+
+private:
+    clang::CompilerInstance &ci;
+};
+
+class TestAction : public ASTFrontendAction {
+    virtual std::unique_ptr<clang::ASTConsumer>
+    CreateASTConsumer(clang::CompilerInstance &ci, llvm::StringRef /*InFile */) override {
+        return std::unique_ptr<TestConsumer>(new TestConsumer(ci));
+    }
+};
+
+}
+
+
+TEST(Decl, LeftoverExpressionsForODRAfterFatalError) {
+  std::vector<std::string> Args(1, "-std=c++11");
+  ASSERT_EXIT({
+      runToolOnCodeWithArgs(
+      new TestAction,
+      "namespace cb {                                                           \n"
+      "/* This first error will guranatee, that we ignore the next error about  \n"
+      " * uknown-type size_t.                                                   \n"
+      " */                                                                      \n"
+      "#include <no-such-header.h>                                              \n"
+      "/**                                                                      \n"
+      " * size_t -- must be not first argument                                  \n"
+      " */                                                                      \n"
+      "extern int callback(int, size_t);                                        \n"
+      "}                                                                        \n"
+      "                                                                         \n"
+      "namespace with_sizet {                                                   \n"
+      "                                                                         \n"
+      "typedef unsigned long size_t;                                            \n"
+      "/** Also it must return something */                                     \n"
+      "int call(int (*__convf) (int, size_t), size_t)                           \n"
+      "{ return 1; }                                                            \n"
+      "                                                                         \n"
+      "}                                                                        \n"
+      "                                                                         \n"
+      "namespace without_sizet {                                                \n"
+      "                                                                         \n"
+      "int to_string(float __val)                                               \n"
+      "{                                                                        \n"
+      "    const int n = 20; /** failed with const qualifier only */            \n"
+      "    return with_sizet::call(&cb::callback, n);                           \n"
+      "}                                                                        \n"
+      "                                                                         \n"
+      "}                                                                        \n",
+      Args);
+      _exit(0);
+  }, ::testing::ExitedWithCode(0), ".*");
+}