ilya-biryukov accepted this revision.
ilya-biryukov added inline comments.
This revision is now accepted and ready to land.
================
Comment at: clang/test/SemaTemplate/concepts-using-decl.cpp:174
+} // namespace heads_without_concepts.
\ No newline at end of file
----------------
NIT: add newline?
================
Comment at: clang/test/SemaTemplate/concepts-using-decl.cpp:112
+ expect<1>(baz{}.foo<Empty>()); // expected-error {{call to member function
'foo' is ambiguous}}
+}
+}
----------------
usaxena95 wrote:
> ilya-biryukov wrote:
> > Could you also check that `requires` clauses and constraints in template
> > parameters do not hide each other?
> > ```
> > template <IsEmpty T> ...
> > // vs
> > template <class T> requires IsEmpty<T> ...
> > // vs
> > template <class T> void foo() requires IsEmpty<T> ...
> > ```
> > Should not hide each other.
> >
> > Another interesting case (that probably does not yet work):
> > ```
> > struct base { template <class T> void foo(); };
> > struct derived : base {
> > using base::foo;
> > template <IsEmpty T> void foo();
> > };
> > ```
> > ^^ `derived().foo<Empty>()` will probably produce an ambiguity now (as we
> > don't have an explicit requires clause here). I don't think it's worth
> > fixing now, but keeping a test for it with a FIXME seems reasonable.
> The last test case would work though since we perform template head check if
> any template head is contrained. This is not ambiguous as overloading chooses
> the "most contrained" version.
Ah, right, this case is not ambiguous to start with. I think I made a mistake
in the description.
The call with `Empty` would work either way and does not check anything:
- we only see a constrained overload => it works,
- we see both overloads, but the one with `IsEmpty` is more specialized => it
works.
I suggest also checking that `derived().foo<int>()` works. In that case the
outcomes are different:
- we only see a constrained overload => compiler error,
- we see both overloads => constrained version does not match and the overload
succeeds.
PS I was definitely under the impression that we are checking for the requires
clause, but not constrained template parameters. However, I now see that I was
wrong and we should also be fine with that case.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D136440/new/
https://reviews.llvm.org/D136440
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