Anastasia added a comment.
In D56735#1358222 <https://reviews.llvm.org/D56735#1358222>, @rjmccall wrote:
> Is there a reason not to just do `T1.getQualifiers() == T2.getQualifiers()`?
I tried this but it causes ObjC test to fail test/SemaObjCXX/arc-overloading.mm.
38 // Simple overloading
39 int &f2(id __strong const *); // expected-note{{candidate function}}
40 float &f2(id __autoreleasing const *); // expected-note{{candidate
function}}
41
42 void test_f2() {
43 id __strong *sip;
44 id __strong const *csip;
45 id __weak *wip;
46 id __autoreleasing *aip;
47 id __unsafe_unretained *uip;
48
49 // Prefer non-ownership conversions to ownership conversions.
50 int &ir1 = f2(sip);
51 int &ir2 = f2(csip);
52 float &fr1 = f2(aip);
53
54 f2(uip); // expected-error{{call to 'f2' is ambiguous}}
55 }
Clang fails to resolve the overloads:
error: 'error' diagnostics seen but not expected:
File /data/llvm/llvm/tools/clang/test/SemaObjCXX/arc-overloading.mm Line
50: call to 'f2' is ambiguous
File /data/llvm/llvm/tools/clang/test/SemaObjCXX/arc-overloading.mm Line
52: call to 'f2' is ambiguous
error: 'note' diagnostics seen but not expected:
File /data/llvm/llvm/tools/clang/test/SemaObjCXX/arc-overloading.mm Line
39: candidate function
File /data/llvm/llvm/tools/clang/test/SemaObjCXX/arc-overloading.mm Line
40: candidate function
File /data/llvm/llvm/tools/clang/test/SemaObjCXX/arc-overloading.mm Line
39: candidate function
File /data/llvm/llvm/tools/clang/test/SemaObjCXX/arc-overloading.mm Line
40: candidate function
Since CVR quals for both overloads of `f2` are the same it didn't continue
ranking the other qualifiers before. But now when it continues looking at the
other qualifiers it finds that `__strong` and `__autoreleasing` are disjoint
and exits at the following return statement in
`CompareQualificationConversions`:
} else {
// Qualifiers are disjoint.
return ImplicitConversionSequence::Indistinguishable;
}
I feel the logic here doesn't apply to this case because it doesn't take into
account that for the passed in function argument there is no ownership
qualification conversion for one of the overloads. But I don't have a good idea
how to fix this easily other than just keep fast pathing ObjC qual here.
May be if we add a separate qualification conversion for ObjC ownership
qualification only we will end up with more conversion steps for one overload
and therefore it will be possible to resolve the ambiguity? Do you have any
other suggestions or do you think someone else could help?
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D56735/new/
https://reviews.llvm.org/D56735
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