Fix another issue introduced by the proposed wording for core issue 1358: since

the instantiation of a constexpr function temploid is now always constexpr, a
defaulted constexpr function temploid is often ill-formed by the rule in
[dcl.fct.def.default]p2 that an explicitly-defaulted constexpr function must
have a constexpr implicit definition. To avoid making loads of completely
reasonable code ill-formed, do not apply that rule to templates.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150453 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 3 deletions

diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 66f045ea8e..4c3c538b61 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -3832,7 +3832,10 @@ void Sema::CheckExplicitlyDefaultedDefaultConstructor(CXXConstructorDecl *CD) {
   // C++11 [dcl.fct.def.default]p2:
   //   An explicitly-defaulted function may be declared constexpr only if it
   //   would have been implicitly declared as constexpr,
-  if (CD->isConstexpr()) {
+  // Do not apply this rule to templates, since core issue 1358 makes such
+  // functions always instantiate to constexpr functions.
+  if (CD->isConstexpr() &&
+      CD->getTemplatedKind() == FunctionDecl::TK_NonTemplate) {
     if (!CD->getParent()->defaultedDefaultConstructorIsConstexpr()) {
       Diag(CD->getLocStart(), diag::err_incorrect_defaulted_constexpr)
         << CXXDefaultConstructor;
@@ -3920,7 +3923,10 @@ void Sema::CheckExplicitlyDefaultedCopyConstructor(CXXConstructorDecl *CD) {
   // C++11 [dcl.fct.def.default]p2:
   //   An explicitly-defaulted function may be declared constexpr only if it
   //   would have been implicitly declared as constexpr,
-  if (CD->isConstexpr()) {
+  // Do not apply this rule to templates, since core issue 1358 makes such
+  // functions always instantiate to constexpr functions.
+  if (CD->isConstexpr() &&
+      CD->getTemplatedKind() == FunctionDecl::TK_NonTemplate) {
     if (!CD->getParent()->defaultedCopyConstructorIsConstexpr()) {
       Diag(CD->getLocStart(), diag::err_incorrect_defaulted_constexpr)
         << CXXCopyConstructor;
@@ -4097,7 +4103,10 @@ void Sema::CheckExplicitlyDefaultedMoveConstructor(CXXConstructorDecl *CD) {
   // C++11 [dcl.fct.def.default]p2:
   //   An explicitly-defaulted function may be declared constexpr only if it
   //   would have been implicitly declared as constexpr,
-  if (CD->isConstexpr()) {
+  // Do not apply this rule to templates, since core issue 1358 makes such
+  // functions always instantiate to constexpr functions.
+  if (CD->isConstexpr() &&
+      CD->getTemplatedKind() == FunctionDecl::TK_NonTemplate) {
     if (!CD->getParent()->defaultedMoveConstructorIsConstexpr()) {
       Diag(CD->getLocStart(), diag::err_incorrect_defaulted_constexpr)
         << CXXMoveConstructor;