Add empty parens to var-to-function renames

lib/Sema/MiscDiagnostics.cpp

@@ -1359,6 +1359,11 @@ void swift::fixItAvailableAttrRename(TypeChecker &TC,
       baseReplace += '.';
     }
     baseReplace += parsed.BaseName;
+    if (parsed.IsFunctionName && parsed.ArgumentLabels.empty() && !call) {
+      // If we're going from a var to a function with no arguments, emit an
+      // empty parameter list.
+      baseReplace += "()";
+    }
     diag.fixItReplace(referenceRange, baseReplace);
   }