Improve our handling of user-defined conversions when computing

implicit conversion sequences. In particular, model the "standard
conversion" from a class to its own type (or a base type) directly as
a standard conversion in the normal path *without* trying to determine
if there is a valid copy constructor. This appears to match the intent
of C++ [over.best.ics]p6 and more closely matches GCC and EDG.

As part of this, model non-lvalue reference initialization via
user-defined conversion in overloading the same way we handle it in
InitializationSequence, separating the "general user-defined
conversion" and "conversion to compatible class type" cases.

The churn in the overload-call-copycon.cpp test case is because the
test case was originally wrong; it assumed that we should do more
checking for copy constructors that we actually should, which affected
overload resolution.

Fixes PR7055. Bootstrapped okay.

llvm-svn: 110773

1 files changed, 16 insertions, 12 deletions

diff --git a/clang/test/SemaCXX/overload-call-copycon.cpp b/clang/test/SemaCXX/overload-call-copycon.cpp
index f57484e5069..6720cb69533 100644
--- a/clang/test/SemaCXX/overload-call-copycon.cpp
+++ b/clang/test/SemaCXX/overload-call-copycon.cpp
@@ -1,40 +1,44 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s -Wnon-pod-varargs
-class X { };
+class X { }; // expected-note {{the implicit copy constructor}} \
+             // expected-note{{the implicit default constructor}}
 
-int& copycon(X x);
+int& copycon(X x); // expected-note{{passing argument to parameter}}
 float& copycon(...);
 
 void test_copycon(X x, X const xc, X volatile xv) {
   int& i1 = copycon(x);
   int& i2 = copycon(xc);
-  float& f1 = copycon(xv);
+  copycon(xv); // expected-error{{no matching constructor}}
 }
 
 class A {
 public:
-  A(A&);
+  A(A&); // expected-note{{would lose const qualifier}} \
+         // expected-note{{no known conversion}}
 };
 
-class B : public A { };
+class B : public A { }; // expected-note{{would lose const qualifier}} \
+// expected-note{{would lose volatile qualifier}} \
+// expected-note 2{{requires 0 arguments}}
 
-short& copycon2(A a);
-int& copycon2(B b);
+short& copycon2(A a); // expected-note{{passing argument to parameter}}
+int& copycon2(B b); // expected-note 2{{passing argument to parameter}}
 float& copycon2(...);
 
 void test_copycon2(A a, const A ac, B b, B const bc, B volatile bv) {
   int& i1 = copycon2(b);
-  float& f1 = copycon2(bc); // expected-warning {{cannot pass object of non-POD type}}
-  float& f2 = copycon2(bv); // expected-warning {{cannot pass object of non-POD type}}
+  copycon2(bc); // expected-error{{no matching constructor}}
+  copycon2(bv); // expected-error{{no matching constructor}}
   short& s1 = copycon2(a);
-  float& f3 = copycon2(ac); // expected-warning {{cannot pass object of non-POD type}}
+  copycon2(ac); // expected-error{{no matching constructor}}
 }
 
-int& copycon3(A a);
+int& copycon3(A a); // expected-note{{passing argument to parameter 'a' here}}
 float& copycon3(...);
 
 void test_copycon3(B b, const B bc) {
   int& i1 = copycon3(b);
-  float& f1 = copycon3(bc); // expected-warning {{cannot pass object of non-POD type}}
+  copycon3(bc); // expected-error{{no matching constructor}}
 }
 
 class C : public B { };