R - fix $typemap() for R specific typemaps

Add support for special variable replacement in the $typemap()
special variable macro for R specific typemaps (rtype, rtypecheck,
scoercein, scoereout).

Author: wsfulton

CHANGES.current

@@ -7,6 +7,11 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2022-10-24: wsfulton
+            [R] Add support for special variable replacement in the $typemap()
+            special variable macro for R specific typemaps (rtype, rtypecheck,
+            scoercein, scoereout).
+
 2022-10-24: wsfulton
 	    [R] Polymorphism in the wrappers was only working for C++ classes,
             now this works for C++ structs too.

Source/Modules/r.cxx

@@ -242,8 +242,8 @@ class R : public Language {
     return status;
   }
 
-  // Not used:
   String *runtimeCode();
+  void replaceSpecialVariables(String *method, String *tm, Parm *parm);
 
 protected:
   int addRegistrationRoutine(String *rname, int nargs);
@@ -2666,6 +2666,16 @@ String * R::runtimeCode() {
   return s;
 }
 
+/*----------------------------------------------------------------------
+ * replaceSpecialVariables()
+ *--------------------------------------------------------------------*/
+
+void R::replaceSpecialVariables(String *method, String *tm, Parm *parm) {
+  (void)method;
+  SwigType *type = Getattr(parm, "type");
+  replaceRClass(tm, type);
+}
+
 
 /* -----------------------------------------------------------------------
  * Called when SWIG wants to initialize this