(* This file is part of the Catala compiler, a specification language for tax and social benefits computation rules. Copyright (C) 2020 Inria, contributor: Alain Delaƫt Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. *) open Shared_ast open Ast open Catala_utils type invariant_status = Fail | Pass | Ignore type invariant_expr = decl_ctx -> typed expr -> invariant_status let check_invariant (inv : string * invariant_expr) (p : typed program) : bool = let name, inv = inv in let result, total, ok = Program.fold_exprs p ~init:(true, 0, 0) ~f:(fun acc e _ty -> (* let currente = e in *) let rec f e (result, total, ok) = let result, total, ok = Expr.shallow_fold f e (result, total, ok) in match inv p.decl_ctx e with | Ignore -> result, total, ok | Fail -> Message.error ~pos:(Expr.pos e) "@[Invariant @{%s@} failed.@,%a@]" name (Print.expr ()) e | Pass -> result, total + 1, ok + 1 in f e acc) in Message.debug "Invariant %s checked.@ result: [%d/%d]" name ok total; result (* Structural invariant: no default can have as type A -> B *) let invariant_default_no_arrow () : string * invariant_expr = ( "default_no_arrow", fun _ctx e -> match Mark.remove e with | EDefault _ -> begin match Mark.remove (Expr.ty e) with TArrow _ -> Fail | _ -> Pass end | _ -> Ignore ) (* Structural invariant: no partial evaluation *) let invariant_no_partial_evaluation () : string * invariant_expr = ( "no_partial_evaluation", fun _ctx e -> match Mark.remove e with | EApp { f; args; _ } -> ( match Mark.remove (Expr.ty f) with | TArrow (tl, _) when List.length args = List.length tl -> Pass | _ -> Fail) | _ -> Ignore ) (* Structural invariant: no function can return an function *) let invariant_no_return_a_function () : string * invariant_expr = ( "no_return_a_function", fun _ctx e -> match Mark.remove e with | EAbs _ -> begin match Mark.remove (Expr.ty e) with | TArrow (_, (TArrow _, _)) -> Fail | _ -> Pass end | _ -> Ignore ) let invariant_app_inversion () : string * invariant_expr = ( "app_inversion", fun _ctx e -> match Mark.remove e with | EApp { f = EAbs { binder; _ }, _; args; _ } -> if Bindlib.mbinder_arity binder = List.length args then Pass else Fail | EApp { f = EVar _, _; _ } -> Pass | EApp { f = EStructAccess _, _; _ } -> Pass | EApp { f = EExternal _, _; _ } -> Pass | EApp _ -> Fail | _ -> Ignore ) (** the arity of constructors when matching is always one. *) let invariant_match_inversion () : string * invariant_expr = ( "match_inversion", fun _ctx e -> match Mark.remove e with | EMatch { cases; _ } -> if EnumConstructor.Map.for_all (fun _ case -> match Mark.remove case with | EAbs { binder; _ } -> Bindlib.mbinder_arity binder = 1 | _ -> false) cases then Pass else Fail | _ -> Ignore ) (* The purpose of these functions is to determine whether the type `TDefault` can only appear in certain positions, such as: * On the left-hand side of an arrow with arity 1, as the type of a scope (for scope calls). * At the root of the type tree (outside a default). * On the right-hand side of the arrow at the root of the type (occurs for rentrant variables). For instance, the following types do follow the invariant: int; bool; int -> bool; ; bool>; int -> ; S_in {x: int -> } -> S {y: bool} While the following types do not follow the invariant: <>; >; -> int; S_in {x: int -> } -> S {y: } This is crucial to maintain the safety of the type system, as demonstrated in the formal development. *) let rec check_typ_no_default ctx ty = match Mark.remove ty with | TLit _ -> true | TTuple ts -> List.for_all (check_typ_no_default ctx) ts | TStruct n -> let s = StructName.Map.find n ctx.ctx_structs in StructField.Map.for_all (fun _k ty -> check_typ_no_default ctx ty) s | TEnum n -> let s = EnumName.Map.find n ctx.ctx_enums in EnumConstructor.Map.for_all (fun _k ty -> check_typ_no_default ctx ty) s | TOption ty -> check_typ_no_default ctx ty | TArrow (args, res) -> List.for_all (check_typ_no_default ctx) args && check_typ_no_default ctx res | TArray ty -> check_typ_no_default ctx ty | TDefault _t -> false | TAny -> Message.error ~internal:true "Some Dcalc invariants are invalid: TAny was found whereas it should be \ fully resolved." | TClosureEnv -> Message.error ~internal:true "Some Dcalc invariants are invalid: TClosureEnv was found whereas it \ should only appear later in the compilation process." let check_type_thunked_or_nodefault ctx ty = check_typ_no_default ctx ty || match Mark.remove ty with | TArrow (args, res) -> ( List.for_all (check_typ_no_default ctx) args && match Mark.remove res with | TDefault ty -> check_typ_no_default ctx ty | _ -> check_typ_no_default ctx ty) | _ -> false let rec check_type_root ctx ty = check_type_thunked_or_nodefault ctx ty || match Mark.remove ty with | TStruct n -> let s = StructName.Map.find n ctx.ctx_structs in ScopeName.Map.exists (fun _k info -> StructName.equal info.in_struct_name n) ctx.ctx_scopes && StructField.Map.for_all (fun _k ty -> match Mark.remove ty with | TDefault ty -> check_typ_no_default ctx ty | _ -> check_type_root ctx ty) s | TArrow ([((TStruct _, _) as tstruct)], res) -> check_type_root ctx tstruct && check_typ_no_default ctx res | TDefault arg -> check_typ_no_default ctx arg | _ -> false let invariant_typing_defaults () : string * invariant_expr = ( "typing_defaults", fun ctx e -> if check_type_root ctx (Expr.ty e) then Pass else ( Message.warning "typing error %a@." (Print.typ ctx) (Expr.ty e); Fail) ) let check_all_invariants prgm = List.fold_left ( && ) true [ check_invariant (invariant_default_no_arrow ()) prgm; check_invariant (invariant_no_partial_evaluation ()) prgm; check_invariant (invariant_no_return_a_function ()) prgm; check_invariant (invariant_app_inversion ()) prgm; check_invariant (invariant_match_inversion ()) prgm; check_invariant (invariant_typing_defaults ()) prgm; ]