Add an explicit diagnostic for the case where an expression is not a constant

expression because it uses 'this'. Inspired by PR20219 comment#2.

llvm-svn: 212433

1 files changed, 7 insertions, 2 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 98061e6c494..3e8a0d0dc14 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -4666,8 +4666,13 @@ public:
     // Can't look at 'this' when checking a potential constant expression.
     if (Info.checkingPotentialConstantExpression())
       return false;
-    if (!Info.CurrentCall->This)
-      return Error(E);
+    if (!Info.CurrentCall->This) {
+      if (Info.getLangOpts().CPlusPlus11)
+        Info.Diag(E, diag::note_constexpr_this) << E->isImplicit();
+      else
+        Info.Diag(E);
+      return false;
+    }
     Result = *Info.CurrentCall->This;
     return true;
   }