Implement Sema::isExprCallable.

We can use this to produce nice diagnostics (and try to fixit-and-recover) in
various cases where we might see "MyFunction" instead of "MyFunction()". The
changes in SemaExpr are an example of how to use isExprCallable.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@130878 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/SemaCXX/member-expr.cpp b/test/SemaCXX/member-expr.cpp
index 68af415..981bae7 100644
--- a/test/SemaCXX/member-expr.cpp
+++ b/test/SemaCXX/member-expr.cpp
@@ -124,10 +124,10 @@
     return fun.x; // expected-error{{base of member reference is an overloaded function; perhaps you meant to call it with no arguments?}}
   }
 
-  S fun2(); // expected-note{{possibly valid overload here}}
-  S fun2(int i); // expected-note{{possibly valid overload here}}
+  S fun2();
+  S fun2(int i);
   int g2() {
-    return fun2.x; // expected-error{{base of member reference is an overloaded function; perhaps you meant to call it?}}
+    return fun2.x; // expected-error{{base of member reference is an overloaded function; perhaps you meant to call it with no arguments?}}
   }
 
   S fun3(int i=0);
@@ -140,4 +140,10 @@
   int g4() {
     return fun4.x; // expected-error{{base of member reference is a function; perhaps you meant to call it?}}
   }
+
+  S fun5(int i); // expected-note{{possibly valid overload here}}
+  S fun5(float f); // expected-note{{possibly valid overload here}}
+  int g5() {
+    return fun5.x; // expected-error{{base of member reference is an overloaded function; perhaps you meant to call it?}}
+  }
 }