clang/test/SemaCXX/cxx2a-three-way-comparison.cpp

   1 // RUN: %clang_cc1 -std=c++2a -verify %s -Wzero-as-null-pointer-constant
   2
   3 // Keep this test before any declarations of operator<=>.
   4 namespace PR44786 {
   5   template<typename T> void f(decltype(T{} <=> T{})) {} // expected-note {{previous}}
   6
   7   struct S {};
   8   int operator<=>(S const &, S const &);
   9   template<typename T> void f(decltype(T{} <=> T{})) {} // expected-error {{redefinition}}
  10 }
  11
  12 struct A {};
  13 constexpr int operator<=>(A a, A b) { return 42; }
  14 static_assert(operator<=>(A(), A()) == 42);
  15
  16 int operator<=>(); // expected-error {{overloaded 'operator<=>' must have at least one parameter of class or enumeration type}}
  17 int operator<=>(A); // expected-error {{overloaded 'operator<=>' must be a binary operator}}
  18 int operator<=>(int, int); // expected-error {{overloaded 'operator<=>' must have at least one parameter of class or enumeration type}}
  19 int operator<=>(A, A, A); // expected-error {{overloaded 'operator<=>' must be a binary operator}}
  20 int operator<=>(A, A, ...); // expected-error {{overloaded 'operator<=>' cannot be variadic}}
  21 int operator<=>(int, A = {}); // expected-error {{parameter of overloaded 'operator<=>' cannot have a default argument}}
  22
  23 struct B {
  24   int &operator<=>(int);
  25   friend int operator<=>(A, B);
  26
  27   friend int operator<=>(int, int); // expected-error {{overloaded 'operator<=>' must have at least one parameter of class or enumeration type}}
  28   void operator<=>(); // expected-error {{overloaded 'operator<=>' must be a binary operator}};
  29   void operator<=>(A, ...); // expected-error {{overloaded 'operator<=>' cannot be variadic}}
  30   void operator<=>(A, A); // expected-error {{overloaded 'operator<=>' must be a binary operator}};
  31 };
  32
  33 int &r = B().operator<=>(0);
  34
  35 namespace PR47893 {
  36   struct A {
  37     void operator<=>(const A&) const;
  38   };
  39   template<typename T> auto f(T a, T b) -> decltype(a < b) = delete;
  40   int &f(...);
  41   int &r = f(A(), A());
  42 }
  43
  44 namespace PR44325 {
  45   struct cmp_cat {};
  46   bool operator<(cmp_cat, void*);
  47   bool operator>(cmp_cat, int cmp_cat::*);
  48
  49   struct X {};
  50   cmp_cat operator<=>(X, X);
  51
  52   bool b1 = X() < X(); // no warning
  53   bool b2 = X() > X(); // no warning
  54
  55   // FIXME: It's not clear whether warning here is useful, but we can't really
  56   // tell that this is a comparison category in general. This is probably OK,
  57   // as comparisons against zero are only really intended for use in the
  58   // implicit rewrite rules, not for explicit use by programs.
  59   bool c = cmp_cat() < 0; // expected-warning {{zero as null pointer constant}}
  60 }