Implement C++11 [expr.call]p11: If the operand to a decltype-specifier is a
function call (or a comma expression with a function call on its right-hand
side), possibly parenthesized, then the return type is not required to be
complete and a temporary is not bound. Other subexpressions inside a decltype
expression do not get this treatment.

This is implemented by deferring the relevant checks for all calls immediately
within a decltype expression, then, when the expression is fully-parsed,
checking the relevant constraints and stripping off any top-level temporary
binding.

Deferring the completion of the return type exposed a bug in overload
resolution where completion of the argument types was not attempted, which
is also fixed by this change.

llvm-svn: 151117
diff --git a/clang/test/SemaCXX/overload-call.cpp b/clang/test/SemaCXX/overload-call.cpp
index 1bbe00f..501e2d6 100644
--- a/clang/test/SemaCXX/overload-call.cpp
+++ b/clang/test/SemaCXX/overload-call.cpp
@@ -534,3 +534,12 @@
     int &ir = (&foo)(0);
   }
 }
+
+namespace IncompleteArg {
+  // Ensure that overload resolution attempts to complete argument types.
+  template<typename T> struct S {
+    friend int f(const S&);
+  };
+  extern S<int> s;
+  int k = f(s);
+}