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

[David Blaikie]

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?

>  // 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
>
>
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