[Format] getFormattingLangOpts: make LS_Auto uses LS_Cpp11 lexing rule

Suggested by sammccall in post-commit review of D65183

Reviewed By: sammccall

Differential Revision: https://reviews.llvm.org/D65194

llvm-svn: 366883

Author: MaskRay

clang/lib/Format/Format.cpp

@@ -2365,11 +2365,14 @@ tooling::Replacements sortUsingDeclarations(const FormatStyle &Style,
 
 LangOptions getFormattingLangOpts(const FormatStyle &Style) {
   LangOptions LangOpts;
+  FormatStyle::LanguageStandard LexingStd =
+      Style.Standard == FormatStyle::LS_Auto ? FormatStyle::LS_Cpp11
+                                             : Style.Standard;
   LangOpts.CPlusPlus = 1;
-  LangOpts.CPlusPlus11 = Style.Standard >= FormatStyle::LS_Cpp11;
-  LangOpts.CPlusPlus14 = Style.Standard >= FormatStyle::LS_Cpp11;
-  LangOpts.CPlusPlus17 = Style.Standard >= FormatStyle::LS_Cpp11;
-  LangOpts.CPlusPlus2a = Style.Standard >= FormatStyle::LS_Cpp11;
+  LangOpts.CPlusPlus11 = LexingStd >= FormatStyle::LS_Cpp11;
+  LangOpts.CPlusPlus14 = LexingStd >= FormatStyle::LS_Cpp11;
+  LangOpts.CPlusPlus17 = LexingStd >= FormatStyle::LS_Cpp11;
+  LangOpts.CPlusPlus2a = LexingStd >= FormatStyle::LS_Cpp11;
   LangOpts.LineComment = 1;
   bool AlternativeOperators = Style.isCpp();
   LangOpts.CXXOperatorNames = AlternativeOperators ? 1 : 0;