PR11614: Mark defaulted special constructors as constexpr if their implicit

definition would satisfy the constexpr requirements.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@147128 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 55 insertions, 0 deletions

diff --git a/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p2.cpp b/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p2.cpp
new file mode 100644
index 0000000000..d401a97ca2
--- /dev/null
+++ b/test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p2.cpp
@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+// An explicitly-defaulted function may be declared constexpr only if it would
+// have been implicitly declared as constexpr.
+struct S1 {
+  constexpr S1() = default; // expected-error {{defaulted definition of default constructor is not constexpr}}
+  constexpr S1(const S1&) = default;
+  constexpr S1(S1&&) = default;
+  constexpr S1 &operator=(const S1&) = default; // expected-error {{explicitly-defaulted copy assignment operator may not have}}
+  constexpr S1 &operator=(S1&&) = default; // expected-error {{explicitly-defaulted move assignment operator may not have}}
+  constexpr ~S1() = default; // expected-error {{destructor cannot be marked constexpr}}
+  int n;
+};
+struct NoCopyMove {
+  constexpr NoCopyMove() {}
+  NoCopyMove(const NoCopyMove&);
+  NoCopyMove(NoCopyMove&&);
+};
+struct S2 {
+  constexpr S2() = default;
+  constexpr S2(const S2&) = default; // expected-error {{defaulted definition of copy constructor is not constexpr}}
+  constexpr S2(S2&&) = default; // expected-error {{defaulted definition of move constructor is not constexpr}}
+  NoCopyMove ncm;
+};
+
+// If a function is explicitly defaulted on its first declaration
+//   -- it is implicitly considered to be constexpr if the implicit declaration
+//      would be
+struct S3 {
+  S3() = default; // expected-note {{here}}
+  S3(const S3&) = default;
+  S3(S3&&) = default;
+  constexpr S3(int n) : n(n) {}
+  int n;
+};
+constexpr S3 s3a = S3(0);
+constexpr S3 s3b = s3a;
+constexpr S3 s3c = S3(); // expected-error {{constant expression}} expected-note {{non-constexpr constructor}}
+
+struct S4 {
+  S4() = default;
+  S4(const S4&) = default; // expected-note {{here}}
+  S4(S4&&) = default; // expected-note {{here}}
+  NoCopyMove ncm;
+};
+constexpr S4 s4a; // ok
+constexpr S4 s4b = S4(); // expected-error {{constant expression}} expected-note {{non-constexpr constructor}}
+constexpr S4 s4c = s4a; // expected-error {{constant expression}} expected-note {{non-constexpr constructor}}
+
+struct S5 {
+  constexpr S5();
+  int n = 1, m = n + 3;
+};
+constexpr S5::S5() = default;
+static_assert(S5().m == 4, "");