[Bug c++/71658] User-defined conversion operator from a wrapper class to the wrapped type does not compile.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71658 --- Comment #3 from Ulrich Mutze --- (In reply to Martin Sebor from comment #1) > I believe the test case is invalid. > > In a call to an operator, operator overload resolution in [over.match.oper] > considers three sets of candidate functions: > 1) member candidates (operators defined as members one of the operands) > 2) non-member candidates (only non-member functions are considered) > 3) built-in candidates (operators that take types to which the operands can > be converted) > > In the test case, sets (1) and (2) are obviously empty. Set (3) is also > empty because there is no well-formed implicit conversion sequence > ([over.best.ics]) from Z1 to int (the conversion exists but would require > two user-defined conversions, one from Z1 to Z and another from Z to int; > such conversions are not well-formed). > > Like GCC, both Clang 3.8 and EDG eccp 3.11 also reject the program. > > The expression "Z(x0)+Z(x1)" is valid because the types of the operands are > Z and thus do not require the second implicit user-defined conversion that > makes set (3) above empty. I believe that (3) is not empty since Z + Z is defined by a member function in Z and the arguments of Z1 + Z1 can be implicitly converted to Z in a single step. The type int is not in the game when Z sum=x0+x1; is under consideration. The implicit conversion Z --> int was enabled simply to allow my function main to return a reasonable value (which is required to be of type int). Sorry for this misleading and superfluous complication in my code.
[Bug c++/71658] User-defined conversion operator from a wrapper class to the wrapped type does not compile.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71658 --- Comment #2 from Ulrich Mutze --- Created attachment 38780 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38780=edit This is a shortened version of the first attachment. It avoids a superfluous complication.
[Bug c++/71658] User-defined conversion operator from a wrapper class to the wrapped type does not compile.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71658 Martin Sebor changed: What|Removed |Added Status|UNCONFIRMED |RESOLVED CC||msebor at gcc dot gnu.org Resolution|--- |INVALID --- Comment #1 from Martin Sebor --- I believe the test case is invalid. In a call to an operator, operator overload resolution in [over.match.oper] considers three sets of candidate functions: 1) member candidates (operators defined as members one of the operands) 2) non-member candidates (only non-member functions are considered) 3) built-in candidates (operators that take types to which the operands can be converted) In the test case, sets (1) and (2) are obviously empty. Set (3) is also empty because there is no well-formed implicit conversion sequence ([over.best.ics]) from Z1 to int (the conversion exists but would require two user-defined conversions, one from Z1 to Z and another from Z to int; such conversions are not well-formed). Like GCC, both Clang 3.8 and EDG eccp 3.11 also reject the program. The expression "Z(x0)+Z(x1)" is valid because the types of the operands are Z and thus do not require the second implicit user-defined conversion that makes set (3) above empty.
