Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  y_0 : V.t
  x_0 : V.t
  K : Z
  Hxs : lsp G x_0 y_0 = Some K
  s0 : VSet.t
  x : V.t
  ============================
   match from_G' (spath_refl G' s0 x) with
   | inl q' => sweight (spath_refl G' s0 x) = sweight q'
   | inr (q1, q2) =>
       sweight (spath_refl G' s0 x) <= sweight q1 - K + sweight q2
   end


DEBUG:Going to execute:
reflexivity
DEBUG LTAC Evaluated term: q