courbet marked an inline comment as done.
courbet 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.
----------------
aaron.ballman wrote:
> 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 Comment is a bit out of date as this is no longer specific to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.
This triggers:
```
else if (ClassTemplateDecl *ClassTemplate
= dyn_cast<ClassTemplateDecl>(Template))
```
Modifying it to:
```
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 {
template <typename U> using toto = typename boost::enable_if<sizeof(U) == 4,
int>::type;
toto<T> f();
};
template <typename T>
struct Bobble {
using type = T;
};
struct Frobble {
using type = char;
};
NonTemplateFunction<Bobble<typename Frobble::type>::type> NTFC;
```
triggers the same path as my previous example, but not the `IsNull()` test.
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D54903/new/
https://reviews.llvm.org/D54903
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