clang/test/SemaCXX/vartemplate-lambda.cpp

   1 // RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify %s
   2
   3 template <class> auto fn0 = [] {};
   4 template <typename> void foo0() { fn0<char>(); }
   5
   6 template<typename T> auto fn1 = [](auto a) { return a + T(1); };
   7 template<typename T> auto v1 = [](int a = T()) { return a; }();
   8 // expected-error@-1{{cannot initialize a parameter of type 'int' with an rvalue of type 'int *'}}
   9 // expected-note@-2{{in instantiation of default function argument expression for 'operator()<int *>' required here}}
  10 // expected-note@-3{{passing argument to parameter 'a' here}}
  11 // expected-note@-4{{substituting into a lambda}}
  12
  13 struct S {
  14   template<class T>
  15   static constexpr T t = [](int f = T(7)){return f;}(); // expected-error{{constexpr variable 't<int>' must be initialized by a constant expression}} expected-note{{cannot be used in a constant expression}}
  16 };
  17
  18 template <typename X>
  19 int foo2() {
  20   X a = 0x61;
  21   fn1<char>(a);
  22   (void)v1<int>;
  23   (void)v1<int *>; // expected-note{{in instantiation of variable template specialization 'v1' requested here}}
  24   (void)S::t<int>; // expected-note{{in instantiation of static data member 'S::t<int>' requested here}}
  25   return 0;
  26 }
  27
  28 template<class C>
  29 int foo3() {
  30   C::m1(); // expected-error{{type 'long long' cannot be used prior to '::' because it has no members}}
  31   return 1;
  32 }
  33
  34 template<class C>
  35 auto v2 = [](int a = foo3<C>()){};  // expected-note{{in instantiation of function template specialization 'foo3<long long>' requested here}}
  36
  37 int main() {
  38   v2<long long>();  // This line causes foo3<long long> to be instantiated.
  39   v2<long long>(2); // This line does not.
  40   foo2<int>();
  41 }