let
  b = a + 1;
  a = 1;
in
a + b
# Alternatives:

# with rec
#rec {
#  b = a + 1;
#  c = a + b;
#  a = 1;
#}

# lists
#rec {
#  b = a + 1;
#  c = a + b;
#  a = 1;
#}

# failing counter-exmaple
#{
#  a = let x = 1; in x;
#  b = x;
#}