Make warnings opt-in for now

Author: kevinushey

inst/NEWS.Rd

@@ -5,10 +5,9 @@
 \section{Changes in [UNRELEASED] Rcpp version 0.11.2}{
   \itemize{
     \item Implicit conversions, e.g. between \code{NumericVector} and
-    \code{IntegerVector}, now throw warnings. These warnings can be
-    disabled by defining \code{\#define RCPP_DONT_WARN_ON_COERCE}
-    before including Rcpp, or by making the conversion explicit with
-    e.g. \code{Rf_coerceVector}.
+    \code{IntegerVector}, will now give warnings if you use
+    \code{\#define RCPP_WARN_ON_COERCE} before including the Rcpp
+    headers.
     \item Templated \code{List} containers, \code{ListOf<T>}, have been 
     introduced. When subsetting such containers, the return is assumed 
     to be of type T, allowing code such as 

inst/include/Rcpp/r_cast.h

@@ -139,7 +139,7 @@ namespace Rcpp{
         if (TYPEOF(x) == TARGET) {
             return x;
         } else {
-            #ifndef RCPP_DONT_WARN_ON_COERCE
+            #ifdef RCPP_WARN_ON_COERCE
             Shield<SEXP> result( internal::r_true_cast<TARGET>(x) );
             Rf_warning("coerced object from '%s' to '%s'",
                 CHAR(Rf_type2str(TYPEOF(x))),