[Bug] Pipelink solver make hotaru beam solver failed to solve

[T0nyX1ang]

Please give the link to the puzzle which causes the bug:

• Link: https://puzz.link/p?firefly/13/13/2.e43e33b13g31g42a23h13b23b32g44c22f4.g13g41h13a41e3.a4.h43g25g11f4.c13e1.d30d23g41f

Please give reproduce steps if possible:

• Step 1: This solver shows no solutions.

[T0nyX1ang]

The bug is pinpointed now.

In the pipelink solver, @zhuyaoyu adds several checks in the common.py -> fill_path() function:

    if directed:
        rule = f"{{ grid_in(R, C, D): direction(D) }} <= 1 :- grid(R, C), {color}(R, C).\n"
        rule += f"{{ grid_out(R, C, D): direction(D) }} <= 1 :- grid(R, C), {color}(R, C)."
        + rule += f"not grid_in(R, C, D) :- grid(R, C), direction(D), not {color}(R, C)."
        + rule += f"not grid_out(R, C, D) :- grid(R, C), direction(D), not {color}(R, C)."
    else:
        rule = f"{{ grid_direction(R, C, D): direction(D) }} :- grid(R, C), {color}(R, C)."
        + rule += f"not grid_direction(R, C, D) :- grid(R, C), direction(D), not {color}(R, C)."

However, this function conflicts with the color definition in firefly(hotaru beam) solver:

    # in restrict_bend function 
    rule += "firefly_all(R, C) :- firefly(R, C).\n"
    rule += "firefly_all(R, C) :- dead_end(R, C).\n"

    # in the main solver
    solver.add_program_line("{ firefly(R, C) } :- grid(R, C), not dead_end(R, C).")
    solver.add_program_line(fill_path(color="firefly", directed=True))

In this way, the rule in fill_path will check 'flrefly(R, C)' instead of firefly_all(R, C), which leads to ignoring dead_end(R, C) that also has a grid_direction(R, C). This will fail the rules newly added.

Fortunately, we find that removing these rules will not influence the Pipe Link solver, and we decide to remove these lines. The commit is just a rollback which will not have any side effects.

[T0nyX1ang]

Fixed in commit bc87911.