Lean.MVarId →
  Lean.FVarId →
    Lean.Meta.FVarSubst →
      Option Lean.Name →
        Lean.LocalDecl →
          (Lean.Expr → Lean.Expr → Lean.MetaM (Option Lean.MVarId)) →
            Lean.Expr → Lean.Expr → Lean.MetaM (Option Lean.Meta.UnifyEqResult)