Improve our handling of user-defined conversions as part of overload
resolution. There are two sources of problems involving user-defined
conversions that this change eliminates, along with providing simpler
interfaces for checking implicit conversions:

  - It eliminates a case of infinite recursion found in Boost.

  - It eliminates the search for the constructor needed to copy a temporary
    generated by an implicit conversion from overload
    resolution. Overload resolution assumes that, if it gets a value
    of the parameter's class type (or a derived class thereof), there
    is a way to copy if... even if there isn't. We now model this
    properly.




git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@101680 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/SemaCXX/user-defined-conversions.cpp b/test/SemaCXX/user-defined-conversions.cpp
index 4367f4b..5de7f44 100644
--- a/test/SemaCXX/user-defined-conversions.cpp
+++ b/test/SemaCXX/user-defined-conversions.cpp
@@ -67,3 +67,18 @@
   Base b4(ctd);
   Base b5 = ctfd;
 }
+
+struct X1 {
+  X1(X1&); // expected-note{{candidate constructor not viable: no known conversion from 'X1' to 'X1 &' for 1st argument}}
+};
+
+struct X2 {
+  operator X1();
+};
+
+int &f(X1);
+float &f(...);
+
+void g(X2 b) {
+  int &ir = f(b); // expected-error{{no viable constructor copying parameter of type 'X1'}}
+}