clang/test/CXX/expr/expr.prim/expr.prim.lambda/p4-cxx14.cpp

   1 // RUN: %clang_cc1 -std=c++23 -fsyntax-only -verify=expected,cxx23    %s
   2 // RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected,cxx14_20 %s
   3 // RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify=expected,cxx14_20 %s
   4
   5 int a;
   6 int &b = [] (int &r) -> decltype(auto) { return r; } (a);
   7 int &c = [] (int &r) -> decltype(auto) { return (r); } (a);
   8 int &d = [] (int &r) -> auto & { return r; } (a);
   9 int &e = [] (int &r) -> auto { return r; } (a); // expected-error {{cannot bind to a temporary}}
  10 int &f = [] (int r) -> decltype(auto) { return r; } (a); // expected-error {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
  11 int &g = [] (int r) -> decltype(auto) { return (r); } (a); // expected-warning {{reference to stack}}
  12 // cxx23-error@-1 {{non-const lvalue reference to type 'int' cannot bind to a temporary of type 'int'}}
  13
  14 int test_explicit_auto_return()
  15 {
  16     struct X {};
  17     auto L = [](auto F, auto a) { return F(a); };
  18     auto M = [](auto a) -> auto { return a; }; // OK
  19     auto MRef = [](auto b) -> auto & { return b; }; //cxx14_20-warning{{reference to stack}}
  20     // cxx23-error@-1 {{non-const lvalue reference to type 'X' cannot bind to a temporary of type 'X'}}
  21     auto MPtr = [](auto c) -> auto* { return &c; }; //expected-warning{{address of stack}}
  22     auto MDeclType = [](auto&& d) -> decltype(auto) { return static_cast<decltype(d)>(d); }; //OK
  23     M(3);
  24
  25     auto &&x = MDeclType(X{});
  26     auto &&x1 = M(X{});
  27     auto &&x2 = MRef(X{});//expected-note{{in instantiation of}}
  28     auto &&x3 = MPtr(X{}); //expected-note{{in instantiation of}}
  29     return 0;
  30 }
  31
  32 int test_implicit_auto_return()
  33 {
  34   {
  35     auto M = [](auto a) { return a; };
  36     struct X {};
  37     X x = M(X{});
  38
  39   }
  40 }
  41
  42 int test_multiple_returns()  {
  43     auto M = [](auto a) {
  44       bool k;
  45       if (k)
  46         return a;
  47       else
  48         return 5; //expected-error{{deduced as 'int' here}}
  49     };
  50     M(3); // OK
  51     M('a'); //expected-note{{in instantiation of}}
  52   return 0;
  53 }
  54 int test_no_parameter_list()
  55 {
  56   static int si = 0;
  57     auto M = [] { return 5; }; // OK
  58     auto M2 = [] -> auto && { return si; };
  59 #if __cplusplus <= 202002L
  60       // expected-warning@-2{{is a C++23 extension}}
  61 #endif
  62     M();
  63 }
  64
  65 int test_conditional_in_return() {
  66   auto Fac = [](auto f, auto n) {
  67     return n <= 0 ? n : f(f, n - 1) * n;
  68   };
  69   // FIXME: this test causes a recursive limit - need to error more gracefully.
  70   //Fac(Fac, 3);
  71
  72 }