"This adds -fconcepts-ts as a cc1 option for enabling the

in-progress implementation of the Concepts TS. The recommended feature
test macro __cpp_experimental_concepts is set to 1 (as opposed to
201501) to indicate that the feature is enabled, but the
implementation is incomplete.

The link to the Concepts TS in cxx_status is updated to refer to the
PDTS (N4377). Additional changes related to __has_feature and
__has_extension are to follow in a later change.

Relevant tests include:

test/Lexer/cxx-features.cpp

The test file is updated with testing of the C++14 + Concepts TS mode.
The expected behaviour is the same as that of the C++14 modes except
for the case of __cpp_experimental_concepts."

- Hubert Tong.

Being committed for Hubert (as per his understanding with Richard Smith) as we start work on the concepts-ts following our preliminary strategy session earlier today. 

The patch is tiny and seems quite standard.

Thanks Hubert!

llvm-svn: 237982

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1537,6 +1537,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.NoMathBuiltin = Args.hasArg(OPT_fno_math_builtin);
   Opts.AssumeSaneOperatorNew = !Args.hasArg(OPT_fno_assume_sane_operator_new);
   Opts.SizedDeallocation = Args.hasArg(OPT_fsized_deallocation);
+  Opts.ConceptsTS = Args.hasArg(OPT_fconcepts_ts);
   Opts.HeinousExtensions = Args.hasArg(OPT_fheinous_gnu_extensions);
   Opts.AccessControl = !Args.hasArg(OPT_fno_access_control);
   Opts.ElideConstructors = !Args.hasArg(OPT_fno_elide_constructors);