r207796 - When sorting overload candidates, sort arity mismatches in ascending

[Kaelyn Takata]

On Thu, May 1, 2014 at 3:26 PM, David Blaikie <dblaikie at gmail.com> wrote:

> On Thu, May 1, 2014 at 2:15 PM, Kaelyn Takata <rikka at google.com> wrote:
> > Author: rikka
> > Date: Thu May  1 16:15:24 2014
> > New Revision: 207796
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=207796&view=rev
> > Log:
> > When sorting overload candidates, sort arity mismatches in ascending
> > order by the number of missing or extra parameters. This is useful if
> > there are more than a few overload candidates with arity mismatches,
> > particularly in the presence of -fshow-overloads=best.
> >
> > Modified:
> >     cfe/trunk/lib/Sema/SemaOverload.cpp
> >     cfe/trunk/test/Misc/error-limit-multiple-notes.cpp
> >
> > Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=207796&r1=207795&r2=207796&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
> > +++ cfe/trunk/lib/Sema/SemaOverload.cpp Thu May  1 16:15:24 2014
> > @@ -9229,7 +9229,10 @@ static unsigned RankDeductionFailure(con
> >
> >  struct CompareOverloadCandidatesForDisplay {
> >    Sema &S;
> > -  CompareOverloadCandidatesForDisplay(Sema &S) : S(S) {}
> > +  size_t NumArgs;
> > +
> > +  CompareOverloadCandidatesForDisplay(Sema &S, size_t nArgs)
> > +      : S(S), NumArgs(nArgs) {}
> >
> >    bool operator()(const OverloadCandidate *L,
> >                    const OverloadCandidate *R) {
> > @@ -9254,8 +9257,18 @@ struct CompareOverloadCandidatesForDispl
> >      if (!L->Viable) {
> >        // 1. Arity mismatches come after other candidates.
> >        if (L->FailureKind == ovl_fail_too_many_arguments ||
> > -          L->FailureKind == ovl_fail_too_few_arguments)
> > +          L->FailureKind == ovl_fail_too_few_arguments) {
> > +        if (R->FailureKind == ovl_fail_too_many_arguments ||
> > +            R->FailureKind == ovl_fail_too_few_arguments) {
> > +          int LDist = abs(L->Function->getNumParams() - NumArgs);
> > +          int RDist = abs(R->Function->getNumParams() - NumArgs);
> > +          if (LDist == RDist)
> > +            return L->FailureKind == ovl_fail_too_many_arguments &&
> > +                   R->FailureKind == ovl_fail_too_few_arguments;
> > +          return LDist < RDist;
> > +        }
> >          return false;
> > +      }
> >        if (R->FailureKind == ovl_fail_too_many_arguments ||
> >            R->FailureKind == ovl_fail_too_few_arguments)
> >          return true;
> > @@ -9442,7 +9455,7 @@ void OverloadCandidateSet::NoteCandidate
> >    }
> >
> >    std::sort(Cands.begin(), Cands.end(),
> > -            CompareOverloadCandidatesForDisplay(S));
> > +            CompareOverloadCandidatesForDisplay(S, Args.size()));
> >
> >    bool ReportedAmbiguousConversions = false;
> >
> >
> > Modified: cfe/trunk/test/Misc/error-limit-multiple-notes.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Misc/error-limit-multiple-notes.cpp?rev=207796&r1=207795&r2=207796&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/test/Misc/error-limit-multiple-notes.cpp (original)
> > +++ cfe/trunk/test/Misc/error-limit-multiple-notes.cpp Thu May  1
> 16:15:24 2014
> > @@ -4,20 +4,22 @@
> >  void foo(int);
> >  void foo(double);
> >  void foo(int, int);
> > +void foo(int, int, int, int);
> >
> >  int main()
> >  {
> > -    foo();
> > +    foo(1, 2, 3);
> >  }
> >
> >  // error and note suppressed by error-limit
> >  struct s1{};
> >  struct s1{};
> >
> > -// CHECK: 10:5: error: no matching function for call to 'foo'
> > -// CHECK: 6:6: note: candidate function not viable: requires 2
> arguments, but 0 were provided
> > -// CHECK: 5:6: note: candidate function not viable: requires 1
> argument, but 0 were provided
> > -// CHECK: 4:6: note: candidate function not viable: requires 1
> argument, but 0 were provided
> > +// CHECK: 11:5: error: no matching function for call to 'foo'
> > +// CHECK: 6:6: note: candidate function not viable: requires 2
> arguments, but 3 were provided
> > +// CHECK: 7:6: note: candidate function not viable: requires 4
> arguments, but 3 were provided
> > +// CHECK: 5:6: note: candidate function not viable: requires 1
> argument, but 3 were provided
> > +// CHECK: 4:6: note: candidate function not viable: requires 1
> argument, but 3 were provided
>
> Would it be appropriate/worthwhile adding some cases where there are
> the same number of arguments but they're of different types? Or in
> that case do we not show the other candidates at all?
>

What exactly do you mean by "same number of arguments but different types"?
If you meant that a candidate accepts the right number of arguments but the
types are wrong, they are already sorted before any arity mismatches. Also,
there are already two one-argument candidates that have different argument
types.


> >  // CHECK: fatal error: too many errors emitted, stopping now
> > -// CHECK-NOT: 15:8: error: redefinition of 's1'
> > -// CHECK-NOT: 14:8: note: previous definition is here
> > +// CHECK-NOT: 16:8: error: redefinition of 's1'
> > +// CHECK-NOT: 15:8: note: previous definition is here
> >
> >
> > _______________________________________________
> > cfe-commits mailing list
> > cfe-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>
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