[LLVMbugs] [Bug 19896] New: Warn if overload resolution picks f(bool) over f(Foo*) when calling f with a const Foo*

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=19896

            Bug ID: 19896
           Summary: Warn if overload resolution picks f(bool) over f(Foo*)
                    when calling f with a const Foo*
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: nicolasweber at gmx.de
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

This:

#include <iostream>
using namespace std;
class Foo {};

class Thingy {
 public:
  // Thingy can contain a bool, or a Foo.
  //static Thingy* newThingy(bool b) {
  //  cout << "Creating bool Thingy" << endl;
  //  return NULL;
  //}
  static Thingy* newThingy(Foo* f) {
    cout << "Creating Foo Thingy" << endl;
    return NULL;
  }
};

class Factory {
 public:
  static const Foo* gimmeFoo() { return new Foo(); }
};

int main() {
  Thingy::newThingy(true);
  Thingy::newThingy(Factory::gimmeFoo());
}


produces

  Creating bool Thingy
  Creating bool Thingy

newThingy(Foo*) can't be called because gimmeFoo() returns a const Foo*.
Because of that, const Foo* doesn't make it into the overload set and
overload-related warnings don't fire. But this is still surprising behavior, so
we should warn on this.

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