exchange alloccol with shallow

Author: ben-schwen

src/assign.c

@@ -461,7 +461,7 @@ SEXP assign(SEXP dt, SEXP rows, SEXP cols, SEXP newcolnames, SEXP values)
     // perform re-overallocation since DT has too less columns #1831 #4100
     if (tl < oldncol+LENGTH(newcolnames)) {
       // use MAX to mitigate case where data is loaded from disk (readRDS()/load()) or constructed manually (e.g. using structure())
-      dt = alloccol(dt, MAX(oldncol-tl, 0) + oldncol + length(newcolnames) + overAlloc, verbose);
+      dt = shallow(dt,R_NilValue, MAX(oldncol-tl, 0) + oldncol + length(newcolnames) + overAlloc);
       tl = TRUELENGTH(dt);
       names = PROTECT(getAttrib(dt, R_NamesSymbol)); protecti++;
     }