Propagate errors from recursive calls in sort

M2/Macaulay2/d/actors3.d

@@ -502,8 +502,8 @@ subsort(l:int,r:int):Expr := (
 	       sortlist.j = tmp;
 	       i = i+1;
 	       j = j-1));
-     if l+1 < j then subsort(l+1,j);
-     if j+1 < r then subsort(j+1,r);
+     if l+1 < j then when subsort(l+1,j) is e:Error do return Expr(e) else nothing;
+     if j+1 < r then when subsort(j+1,r) is e:Error do return Expr(e) else nothing;
      for k from l+1 to j do sortlist.(k-1) = sortlist.k;
      sortlist.j = pivot;
      nullE);

M2/Macaulay2/tests/normal/sort.m2

@@ -87,6 +87,13 @@ assert( L === sort(L, identity) )
 L = {0,0,0,1,2,3}
 assert( L === sort(L, identity) )
 
+-- 49 and 50 are adjacent, so they are always compared, whatever the pivots
+T = new Type of List
+T ? T := (a, b) -> if set {a#0, b#0} === set {49, 50} then error "incomparable" else a#0 ? b#0
+L = apply(100, i -> new T from {i})
+assert try (sort L; false) else true
+assert try (rsort L; false) else true
+
 end
 -- Local Variables:
 -- compile-command: "make -C $M2BUILDDIR/Macaulay2/packages/Macaulay2Doc/test sort.out"