The 'constexpr implies const' rule for non-static member functions is gone in

C++1y, so stop adding the 'const' there. Provide a compatibility warning for
code relying on this in C++11, with a fix-it hint. Update our lazily-written
tests to add the const, except for those ones which were testing our
implementation of this rule.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179969 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 2 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index c20b5ff068..6ecc84fac4 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -6726,9 +6726,12 @@ bool Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
   //
   // This needs to be delayed until we know whether this is an out-of-line
   // definition of a static member function.
+  //
+  // This rule is not present in C++1y, so we produce a backwards
+  // compatibility warning whenever it happens in C++11.
   CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
-  if (MD && MD->isConstexpr() && !MD->isStatic() &&
-      !isa<CXXConstructorDecl>(MD) &&
+  if (!getLangOpts().CPlusPlus1y && MD && MD->isConstexpr() &&
+      !MD->isStatic() && !isa<CXXConstructorDecl>(MD) &&
       (MD->getTypeQualifiers() & Qualifiers::Const) == 0) {
     CXXMethodDecl *OldMD = dyn_cast_or_null<CXXMethodDecl>(OldDecl);
     if (FunctionTemplateDecl *OldTD =
@@ -6743,6 +6746,18 @@ bool Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
                                       ArrayRef<QualType>(FPT->arg_type_begin(),
                                                          FPT->getNumArgs()),
                                           EPI));
+
+      // Warn that we did this, if we're not performing template instantiation.
+      // In that case, we'll have warned already when the template was defined.
+      if (ActiveTemplateInstantiations.empty()) {
+        SourceLocation AddConstLoc;
+        if (FunctionTypeLoc FTL = MD->getTypeSourceInfo()->getTypeLoc()
+                .IgnoreParens().getAs<FunctionTypeLoc>())
+          AddConstLoc = PP.getLocForEndOfToken(FTL.getRParenLoc());
+
+        Diag(MD->getLocation(), diag::warn_cxx1y_compat_constexpr_not_const)
+          << FixItHint::CreateInsertion(AddConstLoc, " const");
+      }
     }
   }