ThreadLocal: Return a mutable pointer if templated with a non-const type

It makes more sense for ThreadLocal<const T>::get to return a const T*
and ThreadLocal<T>::get to return a T*.

llvm-svn: 224225
diff --git a/llvm/unittests/Support/ThreadLocalTest.cpp b/llvm/unittests/Support/ThreadLocalTest.cpp
index ea751be..e71c7db 100644
--- a/llvm/unittests/Support/ThreadLocalTest.cpp
+++ b/llvm/unittests/Support/ThreadLocalTest.cpp
@@ -1,6 +1,6 @@
-//===- llvm/unittest/Support/ThreadLocalTest.cpp - Therad Local tests   ---===//
+//===- llvm/unittest/Support/ThreadLocalTest.cpp - ThreadLocal tests ------===//
 //
-//		       The LLVM Compiler Infrastructure
+//                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
@@ -9,6 +9,7 @@
 
 #include "llvm/Support/ThreadLocal.h"
 #include "gtest/gtest.h"
+#include <type_traits>
 
 using namespace llvm;
 using namespace sys;
@@ -25,6 +26,10 @@
 TEST_F(ThreadLocalTest, Basics) {
   ThreadLocal<const S> x;
 
+  static_assert(
+      std::is_const<std::remove_pointer<decltype(x.get())>::type>::value,
+      "ThreadLocal::get didn't return a pointer to const object");
+
   EXPECT_EQ(nullptr, x.get());
 
   S s;
@@ -33,6 +38,20 @@
 
   x.erase();
   EXPECT_EQ(nullptr, x.get());
+
+  ThreadLocal<S> y;
+
+  static_assert(
+      !std::is_const<std::remove_pointer<decltype(y.get())>::type>::value,
+      "ThreadLocal::get returned a pointer to const object");
+
+  EXPECT_EQ(nullptr, y.get());
+
+  y.set(&s);
+  EXPECT_EQ(&s, y.get());
+
+  y.erase();
+  EXPECT_EQ(nullptr, y.get());
 }
 
 }