PR19415: Converting 'constexpr' to 'const' in a non-static data member can fail
if the member is already 'const'. Don't assert in that case.

llvm-svn: 206205
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index fbc3fd7..65705f5 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -1960,14 +1960,19 @@
         Diag(DS.getConstexprSpecLoc(), diag::err_invalid_constexpr_member);
     SourceLocation ConstexprLoc = DS.getConstexprSpecLoc();
     if (InitStyle == ICIS_NoInit) {
-      B << 0 << 0 << FixItHint::CreateReplacement(ConstexprLoc, "const");
-      D.getMutableDeclSpec().ClearConstexprSpec();
-      const char *PrevSpec;
-      unsigned DiagID;
-      bool Failed = D.getMutableDeclSpec().SetTypeQual(DeclSpec::TQ_const, ConstexprLoc,
-                                         PrevSpec, DiagID, getLangOpts());
-      (void)Failed;
-      assert(!Failed && "Making a constexpr member const shouldn't fail");
+      B << 0 << 0;
+      if (D.getDeclSpec().getTypeQualifiers() & DeclSpec::TQ_const)
+        B << FixItHint::CreateRemoval(ConstexprLoc);
+      else {
+        B << FixItHint::CreateReplacement(ConstexprLoc, "const");
+        D.getMutableDeclSpec().ClearConstexprSpec();
+        const char *PrevSpec;
+        unsigned DiagID;
+        bool Failed = D.getMutableDeclSpec().SetTypeQual(
+            DeclSpec::TQ_const, ConstexprLoc, PrevSpec, DiagID, getLangOpts());
+        (void)Failed;
+        assert(!Failed && "Making a constexpr member const shouldn't fail");
+      }
     } else {
       B << 1;
       const char *PrevSpec;