amend 73758: <NULL>[.] <- <length 0> should work

git-svn-id: https://svn.r-project.org/R/trunk@73773 00db46b3-68df-0310-9c12-caf00c1e9a41

src/main/subassign.c

@@ -1,7 +1,7 @@
 /*
  *  R : A Computer Language for Statistical Data Analysis
- *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
  *  Copyright (C) 1997-2017   The R Core Team
+ *  Copyright (C) 1995, 1996  Robert Gentleman and Ross Ihaka
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -1608,7 +1608,7 @@ SEXP attribute_hidden do_subassign_dflt(SEXP call, SEXP op, SEXP args, SEXP rho)
 	PROTECT(x = PairToVectorList(x));
     }
     else if (xlength(x) == 0) {
-	if (xlength(y) == 0 && TYPEOF(x) == TYPEOF(y)) {
+	if (xlength(y) == 0 && (isNull(x) || TYPEOF(x) == TYPEOF(y))) {
 	    UNPROTECT(1);
 	    return(x);
 	}

tests/reg-tests-1d.R

@@ -1287,6 +1287,10 @@ stopifnot(identical(x0, character()), identical(x1, x0), identical(x, n0))
 ## x0, x1 had remained 'numeric()' in  R <= 3.4.x
 x[1] <- numeric(); stopifnot(identical(x, n0))
 ## had always worked; just checking
+NUL <- NULL
+NUL[3] <- integer(0); NUL[,2] <- character() ; NUL[3,4,5] <- list()
+stopifnot(is.null(NUL))
+## had failed for a few days in R-devel