[clang][Interp] Don't diagnose reading const ints in C++98

We _can_ read them, even in C++98.

Author: tbaederr

clang/lib/AST/Interp/Interp.cpp

@@ -254,10 +254,10 @@ bool CheckConstant(InterpState &S, CodePtr OpPC, const Descriptor *Desc) {
     if (VD->isConstexpr())
       return true;
 
+    QualType T = VD->getType();
     if (S.getLangOpts().CPlusPlus && !S.getLangOpts().CPlusPlus11)
-      return false;
+      return T->isSignedIntegerOrEnumerationType() || T->isUnsignedIntegerOrEnumerationType();
 
-    QualType T = VD->getType();
     if (T.isConstQualified())
       return true;
 

clang/test/AST/Interp/cxx98.cpp

@@ -18,13 +18,12 @@ template struct C<cval>;
 
 /// FIXME: This example does not get properly diagnosed in the new interpreter.
 extern const int recurse1;
-const int recurse2 = recurse1; // both-note {{declared here}}
+const int recurse2 = recurse1; // ref-note {{declared here}}
 const int recurse1 = 1;
 int array1[recurse1];
 int array2[recurse2]; // ref-warning 2{{variable length array}} \
                       // ref-note {{initializer of 'recurse2' is not a constant expression}} \
                       // expected-warning {{variable length array}} \
-                      // expected-note {{read of non-const variable 'recurse2'}} \
                       // expected-error {{variable length array}}
 
 int NCI; // both-note {{declared here}}
@@ -39,3 +38,10 @@ struct V {
                          // both-error {{constructor cannot have a return type}}
 };
 _Static_assert(V().c[0], ""); // both-error {{is not an integral constant expression}}
+
+struct C0 {
+  template<typename U> static U Data; // both-warning {{C++14 extension}}
+  template<typename U> static const U Data<U*> = U();
+};
+const int c0_test = C0::Data<int*>;
+_Static_assert(c0_test == 0, "");