r290577 - Add a test for `const` folding introduced by r290297. NFC.

[George Burgess IV via cfe-commits]

SG; working on a follow-up now. Thanks!

On Mon, Dec 26, 2016 at 8:26 PM, Richard Smith <richard at metafoo.co.uk>
wrote:

> On 26 December 2016 at 20:01, George Burgess IV via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> Author: gbiv
>> Date: Mon Dec 26 22:01:22 2016
>> New Revision: 290577
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=290577&view=rev
>> Log:
>> Add a test for `const` folding introduced by r290297. NFC.
>>
>> AFAICT, we didn't add a test targeted at the new "const can sometimes
>> act as constexpr" behavior introduced by r290297.
>>
>> Modified:
>>     cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp
>>
>> Modified: cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/c
>> onstant-expression-cxx1y.cpp?rev=290577&r1=290576&r2=290577&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/constant-expression-cxx1y.cpp Mon Dec 26
>> 22:01:22 2016
>> @@ -957,3 +957,20 @@ namespace PR27989 {
>>    }
>>    static_assert(f(0) == 1, "");
>>  }
>> +
>> +namespace const_char {
>> +template <int M, int N>
>> +constexpr int sum(const char (&Arr)[N]) {
>> +  static_assert(N >= M, "");
>> +  int S = 0;
>> +  for (unsigned I = 0; I != M; ++I)
>> +    S += Arr[I];
>> +  return S;
>> +}
>> +
>> +// As an extension, we support evaluating some things that are `const`
>> as though
>> +// they were `constexpr`.
>> +const char Cs[] = {'a', 'b', 'c'};
>> +const int N = 2;
>> +static_assert(sum<N>(Cs) == 'a' + 'b', "");
>> +}
>
>
> Hold on, this test should fail. It's OK to extend the set of things we can
> constant-fold, but formal constant expression checking still needs to be
> strict. (You should produce a CCEDiag from within the constant expression
> evaluator to mark things that are not core constant expressions but are
> permitted as an extension.)
>
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