module List = ListLabels module A = Tiger_absyn module Env = Tiger_env module E = Tiger_error module Translate = Tiger_translate module Type = Tiger_env_type module Value = Tiger_env_value (* The only reason for having this seemingly-superfluous inner module is to * have this nice signature as a summary of what each function does. *) module Semant : sig type expty = { exp : Translate.exp ; ty : Type.t } (* Violating normal naming convention just to make it easier to follow * Appel's *) val transExp : env:Env.t -> A.exp -> expty (* transVar does not seem to be needed, as trvar handles all our cases. * Am I wrong? * * val transVar : env:Env.t -> A.var -> expty * *) end = struct type expty = { exp : Translate.exp ; ty : Type.t } let return ty = {exp = (); ty} let return_unit = return Type.Unit let return_nil = return Type.Nil let return_int = return Type.Int let return_string = return Type.String let env_get_typ ~sym ~env ~pos : Type.t = match Env.get_typ env sym with | Some ty -> ty | None -> E.raise (E.Unknown_type {ty_id=sym; pos}) let env_get_val ~sym ~env ~pos : Value.t = match Env.get_val env sym with | Some ty -> ty | None -> E.raise (E.Unknown_id {id=sym; pos}) let check_same {exp=_; ty=ty_left} {exp=_; ty=ty_right} ~pos : unit = if Type.is_equal ty_left ty_right then () else E.raise (E.Wrong_type {expected=ty_left; given=ty_right; pos}) let check_int expty ~pos : unit = check_same {exp=(); ty=Type.Int} expty ~pos (* TODO: actual_ty *) (* TODO: mutual recursion *) let rec transExp ~env exp = let rec trexp exp = (match exp with | A.NilExp -> return_nil | A.IntExp _ -> return_int | A.StringExp {string=_; _} -> return_string | A.CallExp {func; args; pos} -> (match env_get_val ~sym:func ~env ~pos with | Value.Fun {formals; result} -> List.iter2 formals args ~f:(fun ty_expected exp_given -> check_same {exp=(); ty = ty_expected} (trexp exp_given) ~pos; ); return result | Value.Var _ -> E.raise (E.Id_not_a_function {id=func; pos}) ) | A.OpExp {oper; left; right; pos} -> trop oper ~left ~right ~pos | A.RecordExp {fields=field_exps; typ; pos} -> let ty = env_get_typ ~sym:typ ~env ~pos in Type.if_record ty ~f:(fun field_tys -> List.iter field_exps ~f:(fun (field, exp, pos) -> (match List.assoc_opt field field_tys with | Some field_ty -> check_same {exp=(); ty=field_ty} (trexp exp) ~pos | None -> E.raise (E.No_such_field_in_record {field; record=ty; pos}) ) ) ) ~otherwise:(fun () -> E.raise (E.Wrong_type_used_as_record {ty_id=typ; ty; pos}) ); return ty | A.SeqExp [] -> return_unit | A.SeqExp exps -> let last xs = xs |> List.rev (* Yes, redundant, but clean-looking ;-P *) |> List.hd (* Empty is matched in above SeqExp match case *) in exps |> List.map ~f:(fun (exp, _) -> let {ty; _} = trexp exp in ty) |> last |> return | A.AssignExp {var; exp; pos} -> check_same (trvar var) (trexp exp) ~pos; (* TODO: Add var->exp to val env? *) return_unit | A.IfExp {test; then'; else'; pos} -> (* test : must be int, because we have no bool *) (* then : must equal else *) (* else : must equal then or be None *) check_int (trexp test) ~pos; (match (trexp then', else') with | expty_then, None -> expty_then | expty_then, Some else' -> let expty_else = trexp else' in check_same expty_then expty_else ~pos; expty_then ) | A.WhileExp {test; body; pos} -> (* test : must be int, because we have no bool *) check_int (trexp test) ~pos; ignore (trexp body); (* Only care if a type-error is raised *) return_unit | A.ForExp {var; lo; hi; body; pos; escape=_} -> check_int (trexp lo) ~pos; check_int (trexp hi) ~pos; (* Only care if a type-error is raised *) let env = Env.set_val env var (Value.Var {ty = Type.Int}) in ignore (transExp ~env body); return_unit | A.BreakExp _ -> return_unit | A.LetExp {decs; body; pos=_} -> (* (1) decs augment env *) (* (2) body checked against the new env *) let env = List.fold_left decs ~init:env ~f:(fun env dec -> transDec dec ~env) in transExp body ~env | A.ArrayExp {typ; size; init; pos} -> check_int (trexp size) ~pos; let ty = env_get_typ ~sym:typ ~env ~pos in Type.if_array ty ~f:(fun ty_elements -> check_same {exp=(); ty=ty_elements} (trexp init) ~pos ) ~otherwise:(fun () -> E.raise (E.Wrong_type_used_as_array {ty_id=typ; ty; pos}) ); return ty | A.VarExp var -> trvar var ) and trvar = (function | A.SimpleVar {symbol=sym; pos} -> (match env_get_val ~sym ~env ~pos with | Value.Fun _ -> E.raise (E.Id_is_a_function {id=sym; pos}) | Value.Var {ty} -> return ty ) | A.FieldVar {var; symbol; pos} -> let {exp=_; ty} = trvar var in Type.if_record ty ~f:(fun fields -> (match List.assoc_opt symbol fields with | None -> E.raise (E.No_such_field_in_record {field=symbol; record=ty; pos}) | Some ty -> return ty ) ) ~otherwise:(fun () -> E.raise (E.Exp_not_a_record {ty; pos})) | A.SubscriptVar {var; exp; pos} -> let {exp=_; ty} = trvar var in check_int (trexp exp) ~pos; Type.if_array ty ~f:(fun ty_elements -> return ty_elements) ~otherwise:(fun () -> E.raise (E.Exp_not_an_array {ty; pos})) ) and trop oper ~left ~right ~pos = let expty_left = trexp left in let expty_right = trexp right in check_same expty_left expty_right ~pos; let {exp=_; ty} = expty_left in let module T = Type in (match oper with (* Arithmetic: int *) | A.PlusOp | A.MinusOp | A.TimesOp | A.DivideOp -> check_int expty_left ~pos; return_int (* Equality: int, string, array, record *) | A.EqOp | A.NeqOp -> if (T.is_int ty) || (T.is_string ty) || (T.is_array ty) || (T.is_record ty) then return ty else E.raise (E.Invalid_operand_type { oper ; valid = ["int"; "string"; "array"; "record"] ; given = ty ; pos }) (* Order: int, string *) | A.LtOp | A.LeOp | A.GtOp | A.GeOp -> if (T.is_int ty) || (T.is_string ty) then return ty else E.raise (E.Invalid_operand_type { oper ; valid = ["int"; "string"] ; given = ty ; pos }) ) in trexp exp and transDec ~(env : Env.t) (dec : A.dec) : Env.t = (match dec with | A.VarDec {name; typ=typ_opt; init; pos=pos_outter; escape=_} -> let ty = (match (typ_opt, transExp ~env init) with | None, {ty; exp=()} -> ty | Some (sym, pos_inner), expty_init -> let ty = env_get_typ ~sym ~env ~pos:pos_inner in check_same {exp=(); ty} expty_init ~pos:pos_outter; ty ) in Env.set_val env name (Value.Var {ty}) | A.TypeDecs typedecs -> List.fold_left typedecs ~init:env ~f:( fun env (A.TypeDec {name; ty; pos=_}) -> let ty = transTy ~env ty in Env.set_typ env name ty ) | A.FunDecs fundecs -> List.fold_left fundecs ~init:env ~f:( fun env (A.FunDec {name; params; result; body; pos=_}) -> let (env_for_body, formals_in_reverse_order) = List.fold_left params ~init:(env, []) ~f:( fun (env, formals) (A.Field {name; escape=_; typ; pos}) -> let ty = env_get_typ ~env ~sym:typ ~pos in let env = Env.set_val env name (Value.Var {ty}) in (env, ty :: formals) ) in (* ignore because we only care if an exception is raised *) ignore (transExp ~env:env_for_body body); let formals = List.rev formals_in_reverse_order in let result = match result with | None -> Type.Unit | Some (sym, pos) -> env_get_typ ~sym ~env ~pos in Env.set_val env name (Value.Fun {formals; result}) ) ) and transTy ~(env : Env.t) (typ : A.ty) : Type.t = (match typ with | A.NameTy {symbol=sym; pos} -> env_get_typ ~sym ~env ~pos | A.RecordTy fields -> let fields = List.map fields ~f:(fun (A.Field {name; escape=_; typ; pos}) -> let ty = env_get_typ ~sym:typ ~env ~pos in (name, ty) ) in Type.new_record fields | A.ArrayTy {symbol=sym; pos} -> let element_ty = env_get_typ ~sym ~env ~pos in Type.new_array element_ty ) end open Semant let transProg absyn = let {exp = _; ty = _} = transExp absyn ~env:Env.base in ()