clang/test/SemaCXX/constexpr-value-init.cpp

   1 // RUN: %clang_cc1 %s -Wno-uninitialized -std=c++17 -fsyntax-only -verify
   2
   3 struct A {
   4   constexpr A() : a(b + 1), b(a + 1) {} // expected-note 5{{outside its lifetime}}
   5   int a;
   6   int b;
   7 };
   8 struct B { // expected-note {{in call to 'A()'}}
   9   A a;
  10 };
  11
  12 constexpr A a1; // expected-error {{constant expression}} expected-note {{in call to 'A()'}}
  13 constexpr A a2 = A(); // expected-error {{constant expression}} expected-note {{in call to 'A()'}}
  14 void f() {
  15   constexpr A a; // expected-error {{constant expression}} expected-note {{in call to 'A()'}}
  16 }
  17
  18 constexpr B b1; // expected-error {{constant expression}} expected-note {{in call to 'B()'}}
  19 constexpr B b2 = B(); // ok
  20 static_assert(b2.a.a == 1, "");
  21 static_assert(b2.a.b == 2, "");
  22
  23 struct C {
  24   int c;
  25 };
  26 struct D : C { int d; };
  27 constexpr C c1; // expected-error {{without a user-provided default constructor}}
  28 constexpr C c2 = C(); // ok
  29 constexpr D d1; // expected-error {{without a user-provided default constructor}}
  30 constexpr D d2 = D(); // ok with DR1452
  31 static_assert(D().c == 0, "");
  32 static_assert(D().d == 0, "");
  33
  34 struct V : virtual C {};
  35 template<typename T> struct Z : T {
  36   constexpr Z() : V() {}
  37 };
  38 constexpr int n = Z<V>().c; // expected-error {{constant expression}} expected-note {{non-literal type 'Z<V>'}}
  39
  40 struct E { // expected-note {{in call to 'A()'}}
  41   A a[2];
  42 };
  43 constexpr E e1; // expected-error {{constant expression}} expected-note {{in call to 'E()'}}
  44 constexpr E e2 = E();
  45 static_assert(e2.a[0].a == 1, "");
  46 static_assert(e2.a[0].b == 2, "");
  47 static_assert(e2.a[1].a == 1, "");
  48 static_assert(e2.a[1].b == 2, "");
  49
  50 namespace InvalidDeclInsideConstExpr {
  51 template <int a> struct i; // expected-note {{template is declared here}}
  52 template <> struct i<0> {};
  53
  54 template <int x> constexpr auto c() {
  55   // i<x> is valid, but it might be incomplete. g would be invalid in that case.
  56   i<x> g; // expected-error {{implicit instantiation of undefined template 'InvalidDeclInsideConstExpr::i<1>'}}
  57   return 0;
  58 }
  59
  60 auto y = c<1>(); // expected-note {{in instantiation of function template specialization 'InvalidDeclInsideConstExpr::c<1>' requested here}}
  61 auto x = c<0>(); // this is valid.
  62 }