Turn -Wdeprecated-literal-operator on by default

clang/docs/ReleaseNotes.rst

@@ -99,6 +99,20 @@ C++ Specific Potentially Breaking Changes
     // Was error, now evaluates to false.
     constexpr bool b = f() == g();
 
+- The warning ``-Wdeprecated-literal-operator`` is now on by default, as this is
+  something that WG21 has shown interest in removing from the language. The
+  result is that anyone who is compiling with ``-Werror`` should see this
+  diagnostic.  To fix this diagnostic, simply removing the space character from
+  between the ``operator""`` and the user defined literal name will make the
+  source no longer deprecated. This is consistent with `CWG2521 <https://cplusplus.github.io/CWG/issues/2521.html>_`.
+
+  .. code-block:: c++
+
+    // Now diagnoses by default.
+    unsigned operator"" _udl_name(unsigned long long);
+    // Fixed version:
+    unsigned operator""_udl_name(unsigned long long);
+
 ABI Changes in This Version
 ---------------------------
 
@@ -216,6 +230,10 @@ Resolutions to C++ Defect Reports
 - Clang now allows trailing requires clause on explicit deduction guides.
   (`CWG2707: Deduction guides cannot have a trailing requires-clause <https://cplusplus.github.io/CWG/issues/2707.html>`_).
 
+- Clang now diagnoses a space in the first production of a ``literal-operator-id``
+  by default.
+  (`CWG2521: User-defined literals and reserved identifiers <https://cplusplus.github.io/CWG/issues/2521.html>`_).
+
 C Language Changes
 ------------------
 
@@ -378,6 +396,10 @@ Improvements to Clang's diagnostics
 
 - Clang now emits a diagnostic note at the class declaration when the method definition does not match any declaration (#GH110638).
 
+- Clang now emits a ``-Wdepredcated-literal-operator`` diagnostic, even if the
+  name was a reserved name, which we improperly allowed to suppress the
+  diagnostic.
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -439,7 +439,7 @@ def warn_reserved_extern_symbol: Warning<
   InGroup<ReservedIdentifier>, DefaultIgnore;
 def warn_deprecated_literal_operator_id: Warning<
   "identifier %0 preceded by whitespace in a literal operator declaration "
-  "is deprecated">, InGroup<DeprecatedLiteralOperator>, DefaultIgnore;
+  "is deprecated">, InGroup<DeprecatedLiteralOperator>;
 def warn_reserved_module_name : Warning<
   "%0 is a reserved name for a module">, InGroup<ReservedModuleIdentifier>;
 def warn_import_implementation_partition_unit_in_interface_unit : Warning<

clang/lib/Basic/IdentifierTable.cpp

@@ -406,6 +406,9 @@ ReservedLiteralSuffixIdStatus
 IdentifierInfo::isReservedLiteralSuffixId() const {
   StringRef Name = getName();
 
+  // Note: the diag::warn_deprecated_literal_operator_id diagnostic depends on
+  // this being the first check we do, so if this order changes, we have to fix
+  // that as well.
   if (Name[0] != '_')
     return ReservedLiteralSuffixIdStatus::NotStartsWithUnderscore;
 

clang/lib/Sema/SemaExprCXX.cpp

@@ -503,17 +503,23 @@ bool Sema::checkLiteralOperatorId(const CXXScopeSpec &SS,
     const IdentifierInfo *II = Name.Identifier;
     ReservedIdentifierStatus Status = II->isReserved(PP.getLangOpts());
     SourceLocation Loc = Name.getEndLoc();
-    if (!PP.getSourceManager().isInSystemHeader(Loc)) {
-      if (auto Hint = FixItHint::CreateReplacement(
-              Name.getSourceRange(),
-              (StringRef("operator\"\"") + II->getName()).str());
-          isReservedInAllContexts(Status)) {
-        Diag(Loc, diag::warn_reserved_extern_symbol)
-            << II << static_cast<int>(Status) << Hint;
-      } else {
-        Diag(Loc, diag::warn_deprecated_literal_operator_id) << II << Hint;
-      }
-    }
+
+    auto Hint = FixItHint::CreateReplacement(
+        Name.getSourceRange(),
+        (StringRef("operator\"\"") + II->getName()).str());
+
+    // Only emit this diagnostic if we start with an underscore, else the
+    // diagnostic for C++11 requiring a space between the quotes and the
+    // identifier conflicts with this and gets confusing. The diagnostic stating
+    // this is a reserved name should force the underscore, which gets this
+    // back.
+    if (II->isReservedLiteralSuffixId() !=
+        ReservedLiteralSuffixIdStatus::NotStartsWithUnderscore)
+      Diag(Loc, diag::warn_deprecated_literal_operator_id) << II << Hint;
+
+    if (isReservedInAllContexts(Status))
+      Diag(Loc, diag::warn_reserved_extern_symbol)
+          << II << static_cast<int>(Status) << Hint;
   }
 
   if (!SS.isValid())

clang/test/CXX/drs/cwg14xx.cpp

@@ -627,7 +627,7 @@ int i = N::f();
 
 namespace cwg1479 { // cwg1479: 3.1
 #if __cplusplus >= 201103L
-  int operator"" _a(const char*, std::size_t = 0);
+  int operator""_a(const char*, std::size_t = 0);
   // since-cxx11-error@-1 {{literal operator cannot have a default argument}}
 #endif
 }

clang/test/CXX/drs/cwg25xx.cpp

@@ -88,6 +88,9 @@ operator""  _div();
 using ::cwg2521::operator"" _\u03C0___;
 using ::cwg2521::operator""_div;
 // since-cxx11-warning@-2 {{identifier '_π___' preceded by whitespace in a literal operator declaration is deprecated}}
+
+long double operator"" _RESERVED(long double);
+// since-cxx11-warning@-1 {{identifier '_RESERVED' preceded by whitespace in a literal operator declaration is deprecated}}
 #pragma clang diagnostic pop
 #endif
 } // namespace cwg2521

clang/test/CXX/lex/lex.literal/lex.ext/p1.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -Wno-deprecated-literal-operator -verify %s
 
 void operator "" p31(long double); // expected-warning{{user-defined literal suffixes not starting with '_' are reserved}}
 void operator "" _p31(long double);

clang/test/CXX/lex/lex.literal/lex.ext/p10.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -std=c++11 -verify %s
+// RUN: %clang_cc1 -std=c++11 -Wno-deprecated-literal-operator -verify %s
 
 using size_t = decltype(sizeof(int));
 void operator "" wibble(const char *); // expected-warning {{user-defined literal suffixes not starting with '_' are reserved; no literal will invoke this operator}}

clang/test/CXX/lex/lex.literal/lex.ext/p11.cpp

@@ -6,16 +6,16 @@ template<typename T, typename U> struct same_type;
 template<typename T> struct same_type<T, T> {};
 template<typename T> using X = T;
 template<typename CharT, X<CharT>...>
-int operator "" _x(); // expected-warning {{string literal operator templates are a GNU extension}}
+int operator ""_x(); // expected-warning {{string literal operator templates are a GNU extension}}
 template<char...>
-double operator "" _x();
+double operator ""_x();
 
 auto a="string"_x;
 auto b=42_x;
 same_type<decltype(a), int> test_a;
 same_type<decltype(b), double> test_b;
 
-char operator "" _x(const char *begin, size_t size);
+char operator ""_x(const char *begin, size_t size);
 auto c="string"_x;
 auto d=L"string"_x;
 same_type<decltype(c), char> test_c;

clang/test/CXX/lex/lex.literal/lex.ext/p3.cpp

@@ -1,18 +1,18 @@
 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
 
-int &operator "" _x1 (unsigned long long);
+int &operator ""_x1 (unsigned long long);
 int &i1 = 0x123_x1;
 
-double &operator "" _x1 (const char *);
+double &operator ""_x1 (const char *);
 int &i2 = 45_x1;
 
-template<char...> char &operator "" _x1 ();
+template<char...> char &operator ""_x1 ();
 int &i3 = 0377_x1;
 
 int &i4 = 90000000000000000000000000000000000000000000000_x1; // expected-error {{integer literal is too large to be represented in any integer type}}
 
-double &operator "" _x2 (const char *);
+double &operator ""_x2 (const char *);
 double &i5 = 123123123123123123123123123123123123123123123_x2;
 
-template<char...Cs> constexpr int operator "" _x3() { return sizeof...(Cs); }
+template<char...Cs> constexpr int operator ""_x3() { return sizeof...(Cs); }
 static_assert(123456789012345678901234567890123456789012345678901234567890_x3 == 60, "");

clang/test/CXX/lex/lex.literal/lex.ext/p4.cpp

@@ -1,18 +1,18 @@
 // RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
 
-int &operator "" _x1 (long double);
+int &operator ""_x1 (long double);
 int &i1 = 0.123_x1;
 
-double &operator "" _x1 (const char *);
+double &operator ""_x1 (const char *);
 int &i2 = 45._x1;
 
-template<char...> char &operator "" _x1 ();
+template<char...> char &operator ""_x1 ();
 int &i3 = 0377e-1_x1;
 
 int &i4 = 1e1000000_x1; // expected-warning {{too large for type 'long double'}}
 
-double &operator "" _x2 (const char *);
+double &operator ""_x2 (const char *);
 double &i5 = 1e1000000_x2;
 
-template<char...Cs> constexpr int operator "" _x3() { return sizeof...(Cs); }
+template<char...Cs> constexpr int operator ""_x3() { return sizeof...(Cs); }
 static_assert(1e1000000_x3 == 9, "");

clang/test/CXX/lex/lex.literal/lex.ext/p5.cpp

@@ -3,19 +3,19 @@
 
 using size_t = decltype(sizeof(int));
 
-int &operator "" _x1 (const char *);
-double &operator "" _x1 (const char *, size_t);
+int &operator ""_x1 (const char *);
+double &operator ""_x1 (const char *, size_t);
 double &i1 = "foo"_x1;
 #if __cplusplus >= 202002L
 using char8 = float;
-float &operator "" _x1 (const char8_t *, size_t);
+float &operator ""_x1 (const char8_t *, size_t);
 #else
 using char8 = double;
 #endif
 char8 &i2 = u8"foo"_x1;
 double &i3 = L"foo"_x1; // expected-error {{no matching literal operator for call to 'operator""_x1' with arguments of types 'const wchar_t *' and 'unsigned long'}}
 
-char &operator "" _x1(const wchar_t *, size_t);
+char &operator ""_x1(const wchar_t *, size_t);
 char &i4 = L"foo"_x1; // ok
 double &i5 = R"(foo)"_x1; // ok
 char8 &i6 = u\

clang/test/CXX/lex/lex.literal/lex.ext/p6.cpp

@@ -2,13 +2,13 @@
 
 using size_t = decltype(sizeof(int));
 
-int &operator "" _x1 (const char *);
+int &operator ""_x1 (const char *);
 double &i1 = 'a'_x1; // expected-error {{no matching literal operator}}
-double &operator "" _x1 (wchar_t);
+double &operator ""_x1 (wchar_t);
 double &i2 = L'a'_x1;
 double &i3 = 'a'_x1; // expected-error {{no matching literal operator}}
-double &i4 = operator"" _x1('a'); // ok
+double &i4 = operator""_x1('a'); // ok
 
-char &operator "" _x1(char16_t);
+char &operator ""_x1(char16_t);
 char &i5 = u'a'_x1; // ok
 double &i6 = L'a'_x1; // ok

clang/test/CXX/lex/lex.literal/lex.ext/p7.cpp

@@ -10,9 +10,9 @@ template<typename T> struct same_type<T, T> {};
 
 namespace std_example {
 
-long double operator "" _w(long double);
-std::string operator "" _w(const char16_t*, size_t);
-unsigned operator "" _w(const char*);
+long double operator ""_w(long double);
+std::string operator ""_w(const char16_t*, size_t);
+unsigned operator ""_w(const char*);
 int main() {
   auto v1 = 1.2_w;    // calls operator""_w(1.2L)
   auto v2 = u"one"_w; // calls operator""_w(u"one", 3)

clang/test/CXX/lex/lex.literal/lex.ext/p8.cpp

@@ -1,16 +1,16 @@
 // RUN: %clang_cc1 -std=c++11 -verify %s
 
 using size_t = decltype(sizeof(int));
-constexpr const char *operator "" _id(const char *p, size_t) { return p; }
+constexpr const char *operator ""_id(const char *p, size_t) { return p; }
 constexpr const char *s = "foo"_id "bar" "baz"_id "quux";
 
 constexpr bool streq(const char *p, const char *q) {
   return *p == *q && (!*p || streq(p+1, q+1));
 }
 static_assert(streq(s, "foobarbazquux"), "");
 
-constexpr const char *operator "" _trim(const char *p, size_t n) {
-  return *p == ' ' ? operator "" _trim(p + 1, n - 1) : p;
+constexpr const char *operator ""_trim(const char *p, size_t n) {
+  return *p == ' ' ? operator ""_trim(p + 1, n - 1) : p;
 }
 constexpr const char *t = "   " " "_trim "  foo";
 static_assert(streq(t, "foo"), "");

clang/test/CXX/lex/lex.literal/lex.ext/p9.cpp

@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
 
 using size_t = decltype(sizeof(int));
-void operator "" _x(const wchar_t *, size_t);
+void operator ""_x(const wchar_t *, size_t);
 
 namespace std_example {
 

clang/test/CXX/over/over.oper/over.literal/p2.cpp

@@ -1,43 +1,43 @@
 // RUN: %clang_cc1 -std=c++11 %s -verify
 
-void operator "" _a(const char *);
+void operator ""_a(const char *);
 
 namespace N {
-  using ::operator "" _a;
+  using ::operator ""_a;
 
-  void operator "" _b(const char *);
+  void operator ""_b(const char *);
 }
 
-using N::operator "" _b;
+using N::operator ""_b;
 
 class C {
-  void operator "" _c(const char *); // expected-error {{must be in a namespace or global scope}}
+  void operator ""_c(const char *); // expected-error {{must be in a namespace or global scope}}
 
-  static void operator "" _c(unsigned long long); // expected-error {{must be in a namespace or global scope}}
+  static void operator ""_c(unsigned long long); // expected-error {{must be in a namespace or global scope}}
 
-  friend void operator "" _d(const char *);
+  friend void operator ""_d(const char *);
 };
 
-int operator "" _e; // expected-error {{cannot be the name of a variable}}
+int operator ""_e; // expected-error {{cannot be the name of a variable}}
 
 void f() {
-  int operator "" _f; // expected-error {{cannot be the name of a variable}}
+  int operator ""_f; // expected-error {{cannot be the name of a variable}}
 }
 
 extern "C++" {
-  void operator "" _g(const char *);
+  void operator ""_g(const char *);
 }
 
-template<char...> void operator "" _h() {}
+template<char...> void operator ""_h() {}
 
-template<> void operator "" _h<'a', 'b', 'c'>() {}
+template<> void operator ""_h<'a', 'b', 'c'>() {}
 
-template void operator "" _h<'a', 'b', 'c', 'd'>();
+template void operator ""_h<'a', 'b', 'c', 'd'>();
 
 namespace rdar13605348 {
 
 class C {
-  double operator"" _x(long double value) { return double(value); } // expected-error{{literal operator 'operator""_x' must be in a namespace or global scope}}
+  double operator""_x(long double value) { return double(value); } // expected-error{{literal operator 'operator""_x' must be in a namespace or global scope}}
   double value() { return 3.2_x; } // expected-error{{no matching literal operator for call to}}
 };