From a67eb91047ac16ad757fc85eb2b9f35c649acb34 Mon Sep 17 00:00:00 2001
From: Erich Keane <erich.keane@intel.com>
Date: Thu, 19 Jul 2018 13:36:57 +0000
Subject: [PATCH] Enable C++2a Chrono Literals

C++2a via http://wg21.link/p0355 permits the library
literals of 'd' and 'y'. This patch enables them in the
Lexer so that they can be properly parsed.

Note that 'd' gets confused with the hex character, so
modifications to how octal, binary, and decimal numbers are
parsed were required. Since this is simply making previously
invalid code legal, this should be fine.

Hex still greedily parses the 'd' as a hexit, since it would
a: violate [lex.ext]p1
b: break existing code.

Differential Revision: https://reviews.llvm.org/D49504

llvm-svn: 337454
---
 clang/lib/Lex/LiteralSupport.cpp              | 11 +++++---
 .../SemaCXX/cxx2a-user-defined-literals.cpp   | 27 +++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 clang/test/SemaCXX/cxx2a-user-defined-literals.cpp

diff --git a/clang/lib/Lex/LiteralSupport.cpp b/clang/lib/Lex/LiteralSupport.cpp
index e695b2ba3765..966dafca2719 100644
--- a/clang/lib/Lex/LiteralSupport.cpp
+++ b/clang/lib/Lex/LiteralSupport.cpp
@@ -751,7 +751,8 @@ void NumericLiteralParser::ParseDecimalOrOctalCommon(SourceLocation TokLoc){
 
   // If we have a hex digit other than 'e' (which denotes a FP exponent) then
   // the code is using an incorrect base.
-  if (isHexDigit(*s) && *s != 'e' && *s != 'E') {
+  if (isHexDigit(*s) && *s != 'e' && *s != 'E' &&
+      !isValidUDSuffix(PP.getLangOpts(), StringRef(s, ThisTokEnd - s))) {
     PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, s-ThisTokBegin),
             diag::err_invalid_digit) << StringRef(s, 1) << (radix == 8 ? 1 : 0);
     hadError = true;
@@ -804,12 +805,14 @@ bool NumericLiteralParser::isValidUDSuffix(const LangOptions &LangOpts,
   if (!LangOpts.CPlusPlus14)
     return false;
 
-  // In C++1y, "s", "h", "min", "ms", "us", and "ns" are used in the library.
+  // In C++14, "s", "h", "min", "ms", "us", and "ns" are used in the library.
   // Per tweaked N3660, "il", "i", and "if" are also used in the library.
+  // In C++2a "d" and "y" are used in the library.
   return llvm::StringSwitch<bool>(Suffix)
       .Cases("h", "min", "s", true)
       .Cases("ms", "us", "ns", true)
       .Cases("il", "i", "if", true)
+      .Cases("d", "y", LangOpts.CPlusPlus2a)
       .Default(false);
 }
 
@@ -922,7 +925,9 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
     s = SkipBinaryDigits(s);
     if (s == ThisTokEnd) {
       // Done.
-    } else if (isHexDigit(*s)) {
+    } else if (isHexDigit(*s) &&
+               !isValidUDSuffix(PP.getLangOpts(),
+                                StringRef(s, ThisTokEnd - s))) {
       PP.Diag(PP.AdvanceToTokenCharacter(TokLoc, s-ThisTokBegin),
               diag::err_invalid_digit) << StringRef(s, 1) << 2;
       hadError = true;
diff --git a/clang/test/SemaCXX/cxx2a-user-defined-literals.cpp b/clang/test/SemaCXX/cxx2a-user-defined-literals.cpp
new file mode 100644
index 000000000000..d730eba741a8
--- /dev/null
+++ b/clang/test/SemaCXX/cxx2a-user-defined-literals.cpp
@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -std=c++2a %s -include %s -verify
+
+#ifndef INCLUDED
+#define INCLUDED
+
+#pragma clang system_header
+namespace std {
+  namespace chrono {
+    struct day{};
+    struct year{};
+  }
+  constexpr chrono::day operator"" d(unsigned long long d) noexcept;
+  constexpr chrono::year operator"" y(unsigned long long y) noexcept;
+}
+
+#else
+
+using namespace std;
+chrono::day dec_d = 5d;
+chrono::day oct_d = 05d;
+chrono::day bin_d = 0b011d;
+// expected-error@+3{{no viable conversion from 'int' to 'chrono::day'}}
+// expected-note@9{{candidate constructor (the implicit copy constructor)}}
+// expected-note@9{{candidate constructor (the implicit move constructor)}}
+chrono::day hex_d = 0x44d;
+chrono::year y  = 10y;
+#endif