(************************************************************************)
(*         *   The Coq Proof Assistant / The Coq Development Team       *)
(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2018       *)
(* <O___,, *       (see CREDITS file for the list of authors)           *)
(*   \VV/  **************************************************************)
(*    //   *    This file is distributed under the terms of the         *)
(*         *     GNU Lesser General Public License Version 2.1          *)
(*         *     (see LICENSE file for the text of the license)         *)
(************************************************************************)

open Names
open Constr
open Environ
open Reduction

(* Type errors. *)

type 'constr pguard_error =
  (* Fixpoints *)
  | NotEnoughAbstractionInFixBody
  | RecursionNotOnInductiveType of 'constr
  | RecursionOnIllegalTerm of int * (env * 'constr) * int list * int list
  | NotEnoughArgumentsForFixCall of int
  (* CoFixpoints *)
  | CodomainNotInductiveType of 'constr
  | NestedRecursiveOccurrences
  | UnguardedRecursiveCall of 'constr
  | RecCallInTypeOfAbstraction of 'constr
  | RecCallInNonRecArgOfConstructor of 'constr
  | RecCallInTypeOfDef of 'constr
  | RecCallInCaseFun of 'constr
  | RecCallInCaseArg of 'constr
  | RecCallInCasePred of 'constr
  | NotGuardedForm of 'constr
  | ReturnPredicateNotCoInductive of 'constr

type guard_error = constr pguard_error

type arity_error =
  | NonInformativeToInformative
  | StrongEliminationOnNonSmallType
  | WrongArity

type ('constr, 'types) ptype_error =
  | UnboundRel of int
  | UnboundVar of variable
  | NotAType of ('constr, 'types) punsafe_judgment
  | BadAssumption of ('constr, 'types) punsafe_judgment
  | ReferenceVariables of Id.t * 'constr
  | ElimArity of pinductive * Sorts.family list * 'constr * ('constr, 'types) punsafe_judgment
      * (Sorts.family * Sorts.family * arity_error) option
  | CaseNotInductive of ('constr, 'types) punsafe_judgment
  | WrongCaseInfo of pinductive * case_info
  | NumberBranches of ('constr, 'types) punsafe_judgment * int
  | IllFormedBranch of 'constr * pconstructor * 'constr * 'constr
  | Generalization of (Name.t * 'types) * ('constr, 'types) punsafe_judgment
  | ActualType of ('constr, 'types) punsafe_judgment * 'types
  | CantApplyBadType of
      (int * 'constr * 'constr) * ('constr, 'types) punsafe_judgment * ('constr, 'types) punsafe_judgment array
  | CantApplyNonFunctional of ('constr, 'types) punsafe_judgment * ('constr, 'types) punsafe_judgment array
  | IllFormedRecBody of 'constr pguard_error * Name.t array * int * env * ('constr, 'types) punsafe_judgment array
  | IllTypedRecBody of
      int * Name.t array * ('constr, 'types) punsafe_judgment array * 'types array
  | UnsatisfiedConstraints of Univ.Constraint.t
  | UndeclaredUniverse of Univ.Level.t

type type_error = (constr, types) ptype_error

exception TypeError of env * type_error

let nfj env {uj_val=c;uj_type=ct} =
  {uj_val=c;uj_type=nf_betaiota env ct}

let error_unbound_rel env n =
  raise (TypeError (env, UnboundRel n))

let error_unbound_var env v =
  raise (TypeError (env, UnboundVar v))

let error_not_type env j =
  raise (TypeError (env, NotAType j))

let error_assumption env j =
  raise (TypeError (env, BadAssumption j))

let error_reference_variables env id c =
  raise (TypeError (env, ReferenceVariables (id,c)))

let error_elim_arity env ind aritylst c pj okinds =
  raise (TypeError (env, ElimArity (ind,aritylst,c,pj,okinds)))

let error_case_not_inductive env j =
  raise (TypeError (env, CaseNotInductive j))

let error_number_branches env cj expn =
  raise (TypeError (env, NumberBranches (nfj env cj,expn)))

let error_ill_formed_branch env c i actty expty =
  raise (TypeError (env,
    IllFormedBranch (c,i,nf_betaiota env actty, nf_betaiota env expty)))

let error_generalization env nvar c =
  raise (TypeError (env, Generalization (nvar,c)))

let error_actual_type env j expty =
  raise (TypeError (env, ActualType (j,expty)))

let error_cant_apply_not_functional env rator randl =
  raise (TypeError (env, CantApplyNonFunctional (rator,randl)))

let error_cant_apply_bad_type env t rator randl =
  raise (TypeError (env, CantApplyBadType (t,rator,randl)))

let error_ill_formed_rec_body env why lna i fixenv vdefj =
  raise (TypeError (env, IllFormedRecBody (why,lna,i,fixenv,vdefj)))

let error_ill_typed_rec_body env i lna vdefj vargs =
  raise (TypeError (env, IllTypedRecBody (i,lna,vdefj,vargs)))

let error_elim_explain kp ki =
  let open Sorts in
  match kp,ki with
  | (InType | InSet), InProp -> NonInformativeToInformative
  | InType, InSet -> StrongEliminationOnNonSmallType (* if Set impredicative *)
  | _ -> WrongArity

let error_unsatisfied_constraints env c =
  raise (TypeError (env, UnsatisfiedConstraints c))

let error_undeclared_universe env l =
  raise (TypeError (env, UndeclaredUniverse l))