Do not use SET_TYPEOF()

In R-devel r86639 SET_TYPEOF() errors if you try to convert a REAL to
and INTEGER. Create the xts object without using SET_TYPEOF().

Fixes #419.

inst/tinytest/test-merge.R

@@ -245,7 +245,6 @@ empty_with_dims_3x <-
   structure(integer(0), dim = c(0L, 9L), index = .index(x0),
             dimnames = list(NULL, c("a", "b", "c", "a.1", "b.1", "c.1", "a.2", "b.2", "c.2")),
             class = c("xts", "zoo"))
-storage.mode(.index(empty_with_dims_3x)) <- "integer"  ## FIXME: this should be 'numeric
 expect_identical(xm6, empty_with_dims_3x, info = "merge.xts([empty_xts_with_dims 3x]) has correct dims")
 
 

src/merge.c

@@ -366,15 +366,22 @@ SEXP do_merge_xts (SEXP x, SEXP y,
   /* do the inputs have any data to merge? */
   len = nrx + nry;
   if (len < 1 && ncx < 1 && ncy < 1) {
-    /* nothing to do, return empty xts object */
-    SEXP s, t;
-    PROTECT(s = t = allocList(1)); p++;
-    SET_TYPEOF(s, LANGSXP);
-    SETCAR(t, install("xts"));
-    SEXP out = PROTECT(eval(s, env)); p++;
-    SET_TYPEOF(out, TYPEOF(x));
+
+    /* return empty xts object if there are no rows or columns */
+    PROTECT(result = allocVector(TYPEOF(x), 0)); p++;
+    PROTECT(index  = allocVector(TYPEOF(xindex), 0)); p++;
+    setAttrib(index, xts_IndexTzoneSymbol, getAttrib(xindex, xts_IndexTzoneSymbol));
+    setAttrib(index, xts_IndexTclassSymbol, getAttrib(xindex, xts_IndexTclassSymbol));
+    setAttrib(index, xts_IndexTformatSymbol, getAttrib(xindex, xts_IndexTformatSymbol));
+    setAttrib(result, xts_IndexSymbol, index);
+
+    if (LOGICAL(retclass)[0]) {
+      setAttrib(result, R_ClassSymbol, getAttrib(x, R_ClassSymbol));
+    }
+    setAttrib(result, xts_ClassSymbol, getAttrib(x, xts_ClassSymbol));
+
     UNPROTECT(p);
-    return out;
+    return result;
   }
 
   /* Ensure both indexes are REAL if they are not the same type. */