Update constexpr implementation to match CWG's chosen approach for core issues

1358, 1360, 1452 and 1453.
 - Instantiations of constexpr functions are always constexpr. This removes the
   need for separate declaration/definition checking, which is now gone.
 - This makes it possible for a constexpr function to be virtual, if they are
   only dependently virtual. Virtual calls to such functions are not constant
   expressions.
 - Likewise, it's now possible for a literal type to have virtual base classes.
   A constexpr constructor for such a type cannot actually produce a constant
   expression, though, so add a special-case diagnostic for a constructor call
   to such a type rather than trying to evaluate it.
 - Classes with trivial default constructors (for which value initialization can
   produce a fully-initialized value) are considered literal types.
 - Classes with volatile members are not literal types.
 - constexpr constructors can be members of non-literal types. We do not yet use
   static initialization for global objects constructed in this way.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150359 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 11 deletions

diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 7449c62fee..fb771aa30b 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1034,7 +1034,7 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
                            D->getLocation(), D->getDeclName(), T, TInfo,
                            D->getStorageClass(), D->getStorageClassAsWritten(),
                            D->isInlineSpecified(), D->hasWrittenPrototype(),
-                           /*isConstexpr*/ false);
+                           D->isConstexpr());
 
   if (QualifierLoc)
     Function->setQualifierInfo(QualifierLoc);
@@ -1379,7 +1379,7 @@ TemplateDeclInstantiator::VisitCXXMethodDecl(CXXMethodDecl *D,
                                         StartLoc, NameInfo, T, TInfo,
                                         Constructor->isExplicit(),
                                         Constructor->isInlineSpecified(),
-                                        false, /*isConstexpr*/ false);
+                                        false, Constructor->isConstexpr());
   } else if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(D)) {
     Method = CXXDestructorDecl::Create(SemaRef.Context, Record,
                                        StartLoc, NameInfo, T, TInfo,
@@ -1390,7 +1390,7 @@ TemplateDeclInstantiator::VisitCXXMethodDecl(CXXMethodDecl *D,
                                        StartLoc, NameInfo, T, TInfo,
                                        Conversion->isInlineSpecified(),
                                        Conversion->isExplicit(),
-                                       /*isConstexpr*/ false,
+                                       Conversion->isConstexpr(),
                                        Conversion->getLocEnd());
   } else {
     Method = CXXMethodDecl::Create(SemaRef.Context, Record,
@@ -1398,7 +1398,7 @@ TemplateDeclInstantiator::VisitCXXMethodDecl(CXXMethodDecl *D,
                                    D->isStatic(),
                                    D->getStorageClassAsWritten(),
                                    D->isInlineSpecified(),
-                                   /*isConstexpr*/ false, D->getLocEnd());
+                                   D->isConstexpr(), D->getLocEnd());
   }
 
   if (QualifierLoc)
@@ -2305,13 +2305,6 @@ TemplateDeclInstantiator::InitFunctionInstantiation(FunctionDecl *New,
                                                  EPI));
   }
 
-  // C++0x [dcl.constexpr]p6: If the instantiated template specialization of
-  // a constexpr function template satisfies the requirements for a constexpr
-  // function, then it is a constexpr function.
-  if (Tmpl->isConstexpr() &&
-      SemaRef.CheckConstexprFunctionDecl(New, Sema::CCK_Instantiation))
-    New->setConstexpr(true);
-
   const FunctionDecl* Definition = Tmpl;
 
   // Get the definition. Leaves the variable unchanged if undefined.