&nbsp;<span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">Hi swift developers, I get a compile error when try to build standard library in debug with command:`$ swift/utils/build-script --release-debuginfo --debug-swift-stdlib --xcode -c`.The detail error as follow:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">```</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">The following build commands failed:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span class="Apple-tab-span" style="font-family: Helvetica; font-size: 12px; white-space: pre; text-size-adjust: auto;">        </span><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">CompileC /Users/dongmeiliang/Documents/swift-source/build/Xcode-RelWithDebInfoAssert+stdlib-DebugAssert/llvm-macosx-x86_64/tools/clang/utils/TableGen/LLVM.build/RelWithDebInfo/clang-tblgen.build/Objects-normal/x86_64/ClangASTNodesEmitter.o tools/clang/utils/TableGen/ClangASTNodesEmitter.cpp normal x86_64 c++ com.apple.compilers.llvm.clang.1_0.compiler</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">(1 failure)</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">/Users/dongmeiliang/Documents/swift-source/llvm/tools/clang/utils/TableGen/ClangASTNodesEmitter.cpp:50:12: error: no viable conversion from returned value of type 'llvm::Twine' to function return type</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'std::string' (aka 'basic_string&lt;char, char_traits&lt;char&gt;, allocator&lt;char&gt; &gt;')</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;return R.getName() + BaseSuffix;</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;^~~~~~~~~~~~~~~~~~~~~~~~</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/tools/clang/utils/TableGen/ClangASTNodesEmitter.cpp:14:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/TableGen/Record.h:18:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/ADT/ArrayRef.h:13:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/ADT/Hashing.h:49:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/Support/Host.h:17:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/ADT/StringMap.h:17:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/ADT/StringRef.h:13:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/ADT/STLExtras.h:36:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">In file included from /Users/dongmeiliang/Documents/swift-source/llvm/include/llvm/Support/ErrorHandling.h:19:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:763:5: note: candidate constructor not viable: no known conversion from 'llvm::Twine' to</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'const std::__1::basic_string&lt;char&gt; &amp;' for 1st argument</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;basic_string(const basic_string&amp; __str);</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;^</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:768:5: note: candidate constructor not viable: no known conversion from 'llvm::Twine' to</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'std::__1::basic_string&lt;char&gt; &amp;&amp;' for 1st argument</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;basic_string(basic_string&amp;&amp; __str)</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;^</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:778:31: note: candidate constructor not viable: no known conversion from 'llvm::Twine' to</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'const value_type *' (aka 'const char *') for 1st argument</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;_LIBCPP_INLINE_VISIBILITY basic_string(const value_type* __s);</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;^</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/string:810:5: note: candidate constructor not viable: no known conversion from 'llvm::Twine' to</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'initializer_list&lt;value_type&gt;' (aka 'initializer_list&lt;char&gt;') for 1st argument</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;basic_string(initializer_list&lt;value_type&gt; __il);</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">&nbsp;&nbsp;&nbsp;^</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">1 error generated.</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">```</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">My software enviroments:</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">```</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">$ sw_vers</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">ProductName:</span><span class="Apple-tab-span" style="font-family: Helvetica; font-size: 12px; white-space: pre; text-size-adjust: auto;">        </span><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">Mac OS X</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">ProductVersion:</span><span class="Apple-tab-span" style="font-family: Helvetica; font-size: 12px; white-space: pre; text-size-adjust: auto;">        </span><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">10.13.2</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">BuildVersion:</span><span class="Apple-tab-span" style="font-family: Helvetica; font-size: 12px; white-space: pre; text-size-adjust: auto;">        </span><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">17C88</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">$ xcodebuild -version</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">Xcode 9.2</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">Build version 9C40b</span><br style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;"><span style="font-family: Helvetica; font-size: 12px; text-size-adjust: auto;">```</span>