Mark FormatArg::error as noreturn

Summary: Because, if no inlining is enabled, the absence of this attribute caused compile errors due to functions that were expected to return a value not returning a value.

Reviewed By: meyering

Differential Revision: D3698413

fbshipit-source-id: 8f3505b17a2fa7b9710e3fb56d18c6ca00feacb3

folly/FormatArg.h

@@ -211,7 +211,7 @@ inline std::string FormatArg::errorStr(Args&&... args) const {
 }
 
 template <typename... Args>
-inline void FormatArg::error(Args&&... args) const {
+[[noreturn]] inline void FormatArg::error(Args&&... args) const {
   throw BadFormatArg(errorStr(std::forward<Args>(args)...));
 }