rw [eq] at path
c : Char
nfa : NFA
next : Fin nfa.nodes.size
result : { nfa' // nfa.nodes.size < nfa'.nodes.size }
cs : List Char
eq✝ : nfa.pushRegex next (Expr.char c) = result
path : (↑result).pathToNext (↑next) nfa.nodes.size (↑(↑result).start) cs
eq : result = nfa.pushNode (Node.char c ↑next) ⋯
⊢ Expr.matches cs (Expr.char c)
c : Char
nfa : NFA
next : Fin nfa.nodes.size
result : { nfa' // nfa.nodes.size < nfa'.nodes.size }
cs : List Char
eq✝ : nfa.pushRegex next (Expr.char c) = result
path :
  (↑(nfa.pushNode (Node.char c ↑next) ⋯)).pathToNext (↑next) nfa.nodes.size
    (↑(↑(nfa.pushNode (Node.char c ↑next) ⋯)).start) cs
eq : result = nfa.pushNode (Node.char c ↑next) ⋯
⊢ Expr.matches cs (Expr.char c)