(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016     *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
(************************************************************************)

open Names
open Term
open Environ
open Reduction

(* Type errors. *)

type guard_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 arity_error =
  | NonInformativeToInformative
  | StrongEliminationOnNonSmallType
  | WrongArity

type type_error =
  | UnboundRel of int
  | UnboundVar of variable
  | NotAType of unsafe_judgment
  | BadAssumption of unsafe_judgment
  | ReferenceVariables of identifier * constr
  | ElimArity of pinductive * sorts_family list * constr * unsafe_judgment
      * (sorts_family * sorts_family * arity_error) option
  | CaseNotInductive of unsafe_judgment
  | WrongCaseInfo of pinductive * case_info
  | NumberBranches of unsafe_judgment * int
  | IllFormedBranch of constr * pconstructor * constr * constr
  | Generalization of (Name.t * types) * unsafe_judgment
  | ActualType of unsafe_judgment * types
  | CantApplyBadType of
      (int * constr * constr) * unsafe_judgment * unsafe_judgment array
  | CantApplyNonFunctional of unsafe_judgment * unsafe_judgment array
  | IllFormedRecBody of guard_error * Name.t array * int * env * unsafe_judgment array
  | IllTypedRecBody of
      int * Name.t array * unsafe_judgment array * types array
  | UnsatisfiedConstraints of Univ.constraints

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 =
  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))