saar.raz added inline comments.
================
Comment at: lib/AST/ExprCXX.cpp:1478
+ {
+ // We do not want error diagnostics escaping here.
+ Sema::SFINAETrap Trap(S);
----------------
hubert.reinterpretcast wrote:
> saar.raz wrote:
> > faisalv wrote:
> > > Hubert: This needs a TODO: the idea is not to drop SFINAE errors, but to
> > > avoid instantiation that may trigger errors not in the immediate context
> > > of instantiation. The substitution needs to happen piecewise.
> > Could you elaborate/give an example where this handling is inappropriate?
> Determining satisfaction requires normalization (lazy normalization should be
> considered).
> The determination of satisfaction then proceeds by handling the left-hand
> side of conjunction and disjunction constraints before possibly substituting
> into the right-hand side; i.e., there is short-circuiting behaviour.
>
> Example:
> ```
> template <typename T>
> concept C = true;
>
> template <typename T>
> struct Q { static constexpr T value = nullptr; };
>
> template <typename T>
> requires C<T> || T::value
> struct A { };
>
> template <typename T>
> requires C<T> || Q<T>::value
> struct B { };
>
> A<int> a; // okay
> B<int> b; // okay
> ```
>
OK I see your point. You said this should be a TODO - do you think this should
be delayed to a further patch (namely D41569, where we actually deal with
diagnostics and stuff)?
About lazy normalization, I tend to think it is not a good idea - you'll
probably check satisfaction for every defined constraint expression at some
point, and do that many more times than you'd define a new one
Repository:
rC Clang
https://reviews.llvm.org/D41217
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