fix type coercion in bmerge

Author: ben-schwen

R/bmerge.R

@@ -71,7 +71,13 @@ bmerge = function(i, x, icols, xcols, roll, rollends, nomatch, mult, ops, verbos
       stopf("Incompatible join types: %s (%s) and %s (%s). Factor columns must join to factor or character columns.", xname, xclass, iname, iclass)
     }
     if (xclass == iclass) {
-      if (verbose) catf("%s has same type (%s) as %s. No coercion needed.\n", iname, xclass, xname)
+      if (length(icols)>1 && class(x[[xc]])=="Date" && class(i[[ic]]=="Date")) {
+        set(x, j=xc, value=as.double(x[[xc]]))
+        set(i, j=ic, value=as.double(i[[ic]]))
+        if (verbose) catf("%s and %s are both Dates. R does not guarentee a type for Date internally, hence, coercing to double.\n",  iname, xname)
+      } else {
+        if (verbose) catf("%s has same type (%s) as %s. No coercion needed.\n", iname, xclass, xname)
+      }
       next
     }
     if (xclass=="character" || iclass=="character" ||