[PATCH] D135088: [Clang] make canonical AutoType constraints-free

[Matheus Izvekov via Phabricator via cfe-commits]

mizvekov added inline comments.


================
Comment at: clang/lib/Sema/SemaDeclCXX.cpp:8664-8668
+  if (QualType RT = FD->getDeclaredReturnType();
+      DCK == DefaultedComparisonKind::ThreeWay &&
+      RT->getContainedDeducedType() &&
+      (!Context.hasSameType(RT, Context.getAutoDeductType()) ||
+       RT->getContainedAutoType()->isConstrained())) {
----------------
ychen wrote:
> mizvekov wrote:
> > I think this might crash if the three-way comparison is defaulted with a deduced template specialization.
> > 
> > Something like:
> > ```
> > template <class> struct A {};
> > 
> > struct P {
> >   friend A operator<=>(const P&, const P&) = default;
> > };
> > ```
> > 
> > The problem is that `RT->getContainedDeducedType()` will return non-null, because DTSTs are also deduced types, but `RT->getContainedAutoType()` will return null, because DTSTs are not AutoTypes.
> > I think this might crash if the three-way comparison is defaulted with a deduced template specialization.
> > The problem is that `RT->getContainedDeducedType()` will return non-null, because DTSTs are also deduced types, but `RT->getContainedAutoType()` will return null, because DTSTs are not AutoTypes.
> 
> `RT->getContainedAutoType()` will be called only when `RT` is `AutoType`?
Oh right, I see it now, there is a lot going on in that condition :)


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  https://reviews.llvm.org/D135088/new/

https://reviews.llvm.org/D135088