clang/test/SemaCXX/cxx1z-constexpr-lambdas.cpp

// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks %s
// RUN: %clang_cc1 -std=c++1z -verify -fsyntax-only -fblocks -fdelayed-template-parsing %s 
// RUN: %clang_cc1 -std=c++14 -verify -fsyntax-only -fblocks %s -DCPP14_AND_EARLIER


namespace test_lambda_is_literal {
#ifdef CPP14_AND_EARLIER
//expected-error@+4{{not a literal type}}
//expected-note@+2{{not an aggregate and has no constexpr constructors}}
#endif
auto L = [] { };
constexpr int foo(decltype(L) l) { return 0; }

}

#ifndef CPP14_AND_EARLIER
namespace test_constexpr_checking {

namespace ns1 {
  struct NonLit { ~NonLit(); };  //expected-note{{not literal}}
  auto L = [](NonLit NL) constexpr { }; //expected-error{{not a literal type}}
} // end ns1

namespace ns2 {
  auto L = [](int I) constexpr { asm("non-constexpr");  }; //expected-error{{not allowed in constexpr function}}
} // end ns1

} // end ns test_constexpr_checking

namespace test_constexpr_call {

namespace ns1 {
  auto L = [](int I) { return I; };
  static_assert(L(3) == 3);
} // end ns1
namespace ns2 {
  auto L = [](auto a) { return a; };
  static_assert(L(3) == 3);
  static_assert(L(3.14) == 3.14);
}
namespace ns3 {
  auto L = [](auto a) { asm("non-constexpr"); return a; }; //expected-note{{declared here}}
  constexpr int I =  //expected-error{{must be initialized by a constant expression}}
      L(3); //expected-note{{non-constexpr function}}
} 

} // end ns test_constexpr_call

namespace test_captureless_lambda {
void f() {
  const char c = 'c';
  auto L = [] { return c; };
  constexpr char C = L();
}
  
void f(char c) { //expected-note{{declared here}}
  auto L = [] { return c; }; //expected-error{{cannot be implicitly captured}} expected-note{{lambda expression begins here}}
  int I = L();
}

}
#endif // ndef CPP14_AND_EARLIER