Improve R wrapper error message calling overloaded methods

when incorrect types passed are passed to the overloaded methods.

Old unhelpful error message:
  Error in f(...) : could not find function "f"

Example of new improved error message:
  Error in use_count(k) :
    cannot find overloaded function for use_count with argtypes (NULL)

3 files changed, 18 insertions, 6 deletions

diff --git a/CHANGES.current b/CHANGES.current
index 0af67c484..693f8f3bf 100644
--- a/CHANGES.current
+++ b/CHANGES.current
@@ -11,3 +11,13 @@ Version 4.1.1 (in progress)
             [R] #2386 Fix memory leak in R shared_ptr wrappers.
             Fix leak when a cast up a class inheritance chain is required.
 
+2022-10-26: wsfulton
+            [R] Improve R wrapper error message when calling overloaded methods
+            when incorrect types passed are passed to the overloaded methods.
+
+            Old unhelpful error message:
+              Error in f(...) : could not find function "f"
+
+            Example of new improved error message:
+              Error in use_count(k) :
+                cannot find overloaded function for use_count with argtypes (NULL)
diff --git a/Examples/test-suite/r/li_boost_shared_ptr_runme.R b/Examples/test-suite/r/li_boost_shared_ptr_runme.R
index 1f7507337..ec8c66dcf 100644
--- a/Examples/test-suite/r/li_boost_shared_ptr_runme.R
+++ b/Examples/test-suite/r/li_boost_shared_ptr_runme.R
@@ -570,7 +570,7 @@ testSuite <- function() {
     k = m$SmartMemberValue;
     if (!is.null(k))
       stop("expected null");
-    #testSuite_verifyCount(0, k); # this does not work for nulls
+    testSuite_verifyCount(0, k); # this does not work for nulls
 
     # plain by value
     bNotCatched = F
diff --git a/Source/Modules/r.cxx b/Source/Modules/r.cxx
index e1fd422dd..e3d69329b 100644
--- a/Source/Modules/r.cxx
+++ b/Source/Modules/r.cxx
@@ -1566,7 +1566,8 @@ void R::dispatchFunction(Node *n) {
   Printv(f->code,
 	 "argtypes <- mapply(class, list(...));\n",
 	 "argv <- list(...);\n",
-	 "argc <- length(argtypes);\n", NIL );
+	 "argc <- length(argtypes);\n",
+	 "f <- NULL;\n", NIL);
 
   Printf(f->code, "# dispatch functions %d\n", nfunc);
   int cur_args = -1;
@@ -1649,11 +1650,12 @@ void R::dispatchFunction(Node *n) {
     }
   }
   if (cur_args != -1) {
-    Printf(f->code, "} else {\n"
-	   "stop(\"cannot find overloaded function for %s with argtypes (\","
-	   "toString(argtypes),\")\");\n"
-	   "}", sfname);
+    Printf(f->code, "};\n");
   }
+  Printf(f->code, "if (is.null(f)) {\n"
+      "stop(\"cannot find overloaded function for %s with argtypes (\","
+      "toString(argtypes),\")\");\n"
+      "}", sfname);
   Printv(f->code, ";\nf(...)", NIL);
   Printv(f->code, ";\n}", NIL);
   Wrapper_print(f, sfile);