avoid using SET_TYPEOF (#1315)

* avoid using SET_TYPEOF

* try using r_cast

* add coerce helper

* update ChangeLog

* try a shallow duplicate

* CONS macro not available?

* revert un-needed changes

* Rebased and updated

---------

Co-authored-by: Dirk Eddelbuettel <[email protected]>

Author: kevinushey

ChangeLog

@@ -21,6 +21,10 @@
 	* inst/include/Rcpp/Environment.h: Drop support for UserDefinedDatabase
 	[ merged 2024-07-22 after release of Rcpp 1.0.13 ]
 
+	* inst/include/Rcpp/Language.h: Avoid using SET_TYPEOF
+	* inst/include/Rcpp/Pairlist.h: Idem
+	* inst/include/Rcpp/r_cast.h: Idem
+
 2024-06-22  Dirk Eddelbuettel  <[email protected]>
 
 	* DESCRIPTION (Version, Date): Roll micro version

DESCRIPTION

@@ -1,6 +1,6 @@
 Package: Rcpp
 Title: Seamless R and C++ Integration
-Version: 1.0.13.0.1
+Version: 1.0.13.0.2
 Date: 2024-07-22
 Author: Dirk Eddelbuettel, Romain Francois, JJ Allaire, Kevin Ushey, Qiang Kou,
  Nathan Russell, Inaki Ucar, Douglas Bates and John Chambers

inst/include/Rcpp/Language.h

@@ -162,8 +162,10 @@ namespace Rcpp{
             return internal::Rcpp_eval_impl( Storage::get__(), env);
         }
 
-        void update( SEXP x){
-            SET_TYPEOF( x, LANGSXP );
+        void update(SEXP x) {
+            if (TYPEOF(x) != LANGSXP) {
+                Storage::set__(r_cast<LANGSXP>(x));
+            }
             SET_TAG( x, R_NilValue );
         }
 

inst/include/Rcpp/Pairlist.h

@@ -50,8 +50,10 @@ namespace Rcpp{
         #else
             #include <Rcpp/generated/Pairlist__ctors.h>
         #endif
-        void update(SEXP x){
-            SET_TYPEOF( x, LISTSXP ) ;
+        void update(SEXP x) {
+            if (TYPEOF(x) != LISTSXP) {
+                Storage::set__(r_cast<LISTSXP>(x));
+            }
         }
     } ;
 

inst/include/Rcpp/r_cast.h

@@ -143,14 +143,9 @@ namespace Rcpp {
         }
         template<>
         inline SEXP r_true_cast<LISTSXP>(SEXP x) {
-            switch( TYPEOF(x) ){
-            case LANGSXP:
-                {
-                    Shield<SEXP> y( Rf_duplicate( x ));
-                    SET_TYPEOF(y,LISTSXP);
-                    return y;
-                }
-            default:
+            if (TYPEOF(x) == LANGSXP) {
+                return Rf_cons(CAR(x), CDR(x));
+            } else {
                 return convert_using_rfunction(x, "as.pairlist" );
             }
         }