comment

Author: MichaelChirico

src/assign.c

@@ -551,7 +551,7 @@ SEXP assign(SEXP dt, SEXP rows, SEXP cols, SEXP newcolnames, SEXP values)
       if (  MAYBE_SHARED(thisvalue) ||  // set() protects the NAMED of atomic vectors from .Call setting arguments to 2 by wrapping with list
          (TYPEOF(values)==VECSXP && i>LENGTH(values)-1) || // recycled RHS would have columns pointing to others, #185.
          (TYPEOF(values)!=VECSXP && i>0) || // assigning the same values to a second column. Have to ensure a copy #2540
-         ALTREP(thisvalue)
+         ALTREP(thisvalue) // Some ALTREP wrappers have survived to here, e.g. #5400
          ) {
         if (verbose) {
           Rprintf(_("RHS for item %d has been duplicated because MAYBE_REFERENCED==%d MAYBE_SHARED==%d ALTREP==%d, but then is being plonked. length(values)==%d; length(cols)==%d\n"),