aaron.ballman added inline comments.
================
Comment at: lib/Sema/SemaTemplate.cpp:3055
+// Print a diagnostic for the failing static_assert expression. Defaults to
+// pretty-printing the expression.
----------------
courbet wrote:
> aaron.ballman wrote:
> > Comment is a bit out of date as this is no longer specific to
> > `static_assert`.
> >
> > It looks like this may also change the behavior of enable_if diagnostic
> > reporting. Do you need to update any of those tests from this change? If
> > not, can you devise some tests for that case as well to show that this
> > isn't just a static_assert behavior? (Do a search for
> > `findFailedBooleanCondition` to find where the behavior has changed.)
> Nope, unfortunately the code that calls this is actually untested...
> I could not find a test that actually enters the:
> ```
> if (TypeAliasTemplateDecl *AliasTemplate =
> dyn_cast<TypeAliasTemplateDecl>(Template))
> ```
> in `Sema::CheckTemplateIdType`.
>
> I stopped at the following insanity:
>
> ```
> // RUN: %clang_cc1 -std=c++11 -verify %s
>
> template <typename T, typename U>
> struct is_same {
> enum { value = 0 };
> };
>
> template <typename T> struct is_same<T, T> {
> enum { value = 1 };
> };
>
> struct Dispatch {
> template <typename T> using SameAs = is_same<int, T>;
> };
>
> template <typename DispatchT>
> struct S {
> template <typename T> using same = typename DispatchT::template SameAs<T>;
>
> template <typename T>
> static void foo() __attribute__((enable_if(same<T>::value, "")));
>
> };
>
> void runFoo() {
> // S<Dispatch>::foo<int>();
> S<FailedDispatch>::foo<float>();
>
> }
> ```
>
> This one exercises the code up to `if (CanonType.isNull()) {`, but I'm not
> sure how to get a null type here.
>
How about this:
```
namespace boost {
template<bool, typename = void> struct enable_if {};
template<typename T> struct enable_if<true, T> { typedef T type; };
}
template<typename T> struct NonTemplateFunction {
typename boost::enable_if<sizeof(T) == 4, int>::type f();
};
template <typename T>
struct Bobble {
using type = T;
};
struct Frobble {
using type = char;
};
NonTemplateFunction<Bobble<typename Frobble::type>::type> NTFC;
```
That should trigger the path in `Sema::CheckTypenameType()`, I believe.
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D54903/new/
https://reviews.llvm.org/D54903
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