aaron.ballman added inline comments.
================
Comment at: clang-tidy/misc/ForwardingReferenceOverloadCheck.cpp:125-126
+ }
+ diag(Ctor->getLocation(), "function %0 can hide copy and move
constructors")
+ << Ctor;
+ }
----------------
leanil wrote:
> aaron.ballman wrote:
> > xazax.hun wrote:
> > > aaron.ballman wrote:
> > > > xazax.hun wrote:
> > > > > aaron.ballman wrote:
> > > > > > aaron.ballman wrote:
> > > > > > > leanil wrote:
> > > > > > > > aaron.ballman wrote:
> > > > > > > > > I think a better diagnostic might be: "constructor accepting
> > > > > > > > > a universal reference hides the %select{copy|move|both the
> > > > > > > > > copy and move}0 %select{constructor{|s}1"
> > > > > > > > >
> > > > > > > > > And then provide a note ("%select{copy|move}0 constructor
> > > > > > > > > declared here") that points to the offending copy and/or move
> > > > > > > > > constructor.
> > > > > > > > Without checking actual constructor calls, I would have to make
> > > > > > > > notes on every (non disabled) copy / move constructor, any time
> > > > > > > > I produce a warning. And as the warning already states where
> > > > > > > > the problem lies, the notes would only help people find the
> > > > > > > > copy and move constructors. Do you think that's necessary?
> > > > > > > The warning states where the forwarding reference constructor is,
> > > > > > > but it doesn't state where the conflicting constructors are. When
> > > > > > > we issue diagnostics like that, we generally use notes so that
> > > > > > > the user can see all of the locations involved -- the user may
> > > > > > > want to get rid of the other constructors, or they may want to
> > > > > > > get rid of the forwarding reference constructor. Also, saying
> > > > > > > "can hide" implies that it isn't hiding anything at all, just
> > > > > > > that it's possible to do so. Tightening up the wording and
> > > > > > > showing all of the locations involved solves both problems.
> > > > > > This isn't quite complete. It's still an ambiguous statement to say
> > > > > > "it can hide"; it does hide these constructors, and we even know
> > > > > > which ones. Emit the notes before you emit the main diagnostic and
> > > > > > you can use the `%select` suggested originally to be specific in
> > > > > > the diagnostic.
> > > > > We can not say for sure without looking at a concrete call whether a
> > > > > constructor is "hidden" or not. It is always determined during the
> > > > > overload resolution.
> > > > >
> > > > > This check does not consider the calls, because that way it would
> > > > > always miss the possible misuses if libraries.
> > > > I can see the logic in that. I guess I'm thinking of it the same way we
> > > > use the phrase "hidden" when describing code like:
> > > > ```
> > > > struct Base {
> > > > virtual void f(int);
> > > > };
> > > >
> > > > struct Derived : Base {
> > > > void f(double);
> > > > };
> > > >
> > > > ```
> > > > We claim Derived::f() hides Base::f() without considering the callers.
> > > I see. In that case maybe we should come up with a less confusing term
> > > like hijacking overload? The constructors are still part of the overload
> > > set, so no hiding as in the standard's nomenclature happens here, but the
> > > overload resolution is not doing what the user would expect in these
> > > cases.
> > I'm also fine going back to being somewhat more wishy-washy in our phrasing
> > (can hide).
> >
> > What do you think about using the %select to specify what can be hidden,
> > rather than always talking about copy and move constructors (one of which
> > may not even be present in the user's source)?
> I think the (assumed) use of a compiler generated copy or move is similarly
> problematic as in the case of a user defined one, so I would keep mentioning
> both.
That would be handled automatically anyway (the select I suggested has an
option for both). Also, you should have a test for the case involving the
implicitly declared constructors.
================
Comment at: clang-tidy/misc/ForwardingReferenceOverloadCheck.cpp:127
+ << Ctor;
+ for (auto OtherCtor : Ctor->getParent()->ctors()) {
+ if (OtherCtor->isCopyConstructor() || OtherCtor->isMoveConstructor()) {
----------------
Should be `const auto *` rather than just `auto`.
================
Comment at: clang-tidy/misc/ForwardingReferenceOverloadCheck.cpp:131
+ "%select{copy|move}0 constructor declared here",
DiagnosticIDs::Note)
+ << OtherCtor->isMoveConstructor() << OtherCtor;
+ }
----------------
This passes in too many arguments to the diagnostic, I think `OtherCtor` should
be removed.
Repository:
rL LLVM
https://reviews.llvm.org/D30547
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