%{
(* START HEADER *)

[@@@warning "-42"]

open Region
module AST = Parser_cameligo.AST
open! AST

type 'a sequence_elements = {
  s_elts       : ('a, semi) Utils.nsepseq;
  s_terminator : semi option
}

type 'a record_elements = {
  r_elts       : (field_assign reg, semi) Utils.nsepseq;
  r_terminator : semi option
}

type 'a sequence_or_record =
  PaSequence   of 'a sequence_elements
| PaRecord     of 'a record_elements
| PaSingleExpr of expr

let (<@) f g x = f (g x)

(*
  Convert a nsepseq to a chain of TFun's.

  Necessary to handle cases like:
  [type foo = (int, int) => int;]
*)

let rec curry hd = function
  (sep, item)::rest ->
    let stop   = nsepseq_to_region type_expr_to_region (hd, rest)
    and start  = type_expr_to_region hd in
    let region = cover start stop
    and value  = hd, sep, curry item rest
    in TFun {value; region}
| [] -> hd

(* END HEADER *)
%}

(* See [ParToken.mly] for the definition of tokens. *)

(* Entry points *)

%start contract interactive_expr
%type <AST.t> contract
%type <AST.expr> interactive_expr

(* Solves a shift/reduce problem that happens with record and
   sequences. To elaborate: [sequence_or_record_in]
   can be reduced to [expr -> Ident], but also to
   [field_assignment -> Ident].
*)

%nonassoc Ident
%nonassoc COLON

%%

(* RULES *)

(* The rule [sep_or_term(item,sep)] ("separated or terminated list")
   parses a non-empty list of items separated by [sep], and optionally
   terminated by [sep]. *)

sep_or_term_list(item,sep):
  nsepseq(item,sep) {
    $1, None
  }
| nseq(item sep {$1,$2}) {
    let (first,sep), tail = $1 in
    let rec trans (seq, prev_sep as acc) = function
      [] -> acc
    | (item,next_sep)::others ->
        trans ((prev_sep,item)::seq, next_sep) others in
    let list, term = trans ([],sep) tail
    in (first, List.rev list), Some term }

(* Compound constructs *)

par(X):
  "(" X ")" {
    let region = cover $1 $3
    and value  = {lpar=$1; inside=$2; rpar=$3}
    in {region; value} }

(* Sequences

   Series of instances of the same syntactical category have often to
   be parsed, like lists of expressions, patterns etc. The simplest of
   all is the possibly empty sequence (series), parsed below by
   [seq]. The non-empty sequence is parsed by [nseq]. Note that the
   latter returns a pair made of the first parsed item (the parameter
   [X]) and the rest of the sequence (possibly empty). This way, the
   OCaml typechecker can keep track of this information along the
   static control-flow graph. The rule [sepseq] parses possibly empty
   sequences of items separated by some token (e.g., a comma), and
   rule [nsepseq] is for non-empty such sequences. See module [Utils]
   for the types corresponding to the semantic actions of those
   rules.
*)

(* Possibly empty sequence of items *)

seq(item):
  (**)           {     [] }
| item seq(item) { $1::$2 }

(* Non-empty sequence of items *)

nseq(item):
  item seq(item) { $1,$2 }

(* Non-empty separated sequence of items *)

nsepseq(item,sep):
  item                       {                        $1, [] }
| item sep nsepseq(item,sep) { let h,t = $3 in $1, ($2,h)::t }

(* Helpers *)

%inline type_name   : "<ident>"  { $1 }
%inline field_name  : "<ident>"  { $1 }
%inline struct_name : "<ident>"  { $1 }
%inline module_name : "<constr>" { $1 }

(* Non-empty comma-separated values (at least two values) *)

tuple(item):
  item "," nsepseq(item,",") { let h,t = $3 in $1,($2,h)::t }

(* Possibly empty semicolon-separated values between brackets *)

list__(item):
  "[" sep_or_term_list(item,";")? "]" {
    let compound = Brackets ($1,$3)
    and region = cover $1 $3 in
    let elements, terminator =
      match $2 with
        None -> None, None
      | Some (elements, terminator) ->
          Some elements, terminator in
    let value = {compound; elements; terminator}
    in {region; value} }

(* Main *)

contract:
  declarations EOF { {decl=$1; eof=$2} }

declarations:
  declaration              { $1,[] : AST.declaration Utils.nseq }
| declaration declarations { Utils.nseq_cons $1 $2              }

declaration:
| type_decl ";"?           { TypeDecl $1 }
| let_declaration ";"?     { Let      $1 }

(* Type declarations *)

type_decl:
  "type" type_name "=" type_expr {
    Scoping.check_reserved_name $2;
    let region = cover $1 (type_expr_to_region $4)
    and value = {kwd_type   = $1;
                 name       = $2;
                 eq         = $3;
                 type_expr  = $4}
    in {region; value} }

type_expr:
  fun_type | sum_type | record_type { $1 }

fun_type:
  type_name "=>" fun_type {
    let region = cover $1.region (type_expr_to_region $3)
    in TFun {region; value = TVar $1, $2, $3}
  }
| "(" fun_type ")" "=>" fun_type {
    let region = cover $1 (type_expr_to_region $5)
    in TFun {region; value = $2,$4,$5}
  }
| "(" tuple(fun_type) ")" "=>" fun_type {
    let hd, rest = $2 in curry hd (rest @ [($4,$5)])
  }
| "(" tuple(fun_type) ")" {
    TProd {region = cover $1 $3; value = $2}
  }
| core_type { $1 }

type_args:
  tuple(fun_type) {     $1 }
| fun_type        { $1, [] }

core_type:
  type_name      { TVar $1 }
| par(fun_type)  { TPar $1 }
| module_name "." type_name {
    let module_name = $1.value in
    let type_name   = $3.value in
    let value       = module_name ^ "." ^ type_name in
    let region      = cover $1.region $3.region
    in TVar {region; value}
  }
| type_name par(type_args) {
   let region = cover $1.region $2.region
   in TApp {region; value = $1,$2} }

sum_type:
  ioption("|") nsepseq(variant,"|") {
    Scoping.check_variants (Utils.nsepseq_to_list $2);
    let region = nsepseq_to_region (fun x -> x.region) $2
    in TSum {region; value=$2} }

variant:
  "<constr>" { {$1 with value={constr=$1; arg=None}} }
| "<constr>" "(" fun_type ")" {
    let region = cover $1.region $4
    and value  = {constr=$1; arg = Some (ghost,$3)}
    in {region; value} }

record_type:
  "{" sep_or_term_list(field_decl,",") "}" {
    let ne_elements, terminator = $2 in
    let () = Utils.nsepseq_to_list ne_elements
             |> Scoping.check_fields in
    let region = cover $1 $3
    and value  = {compound = Braces ($1,$3); ne_elements; terminator}
    in TRecord {region; value} }

type_expr_field:
  core_type | sum_type | record_type { $1 }

field_decl:
  field_name {
    let value = {field_name=$1; colon=ghost; field_type = TVar $1}
    in {$1 with value}
  }
| field_name ":" type_expr_field {
    let stop   = type_expr_to_region $3 in
    let region = cover $1.region stop
    and value  = {field_name=$1; colon=$2; field_type=$3}
    in {region; value} }

(* Top-level definitions *)

let_declaration:
  seq(Attr) "let" ioption("rec") let_binding {
    let attributes = $1 in
    let kwd_let    = $2 in
    let kwd_rec    = $3 in
    let binding    = $4 in
    let value      = kwd_let, kwd_rec, binding, attributes in
    let stop       = expr_to_region binding.let_rhs in
    let region     = cover $2 stop
    in {region; value} }

let_binding:
  "<ident>" type_annotation? "=" expr {
    Scoping.check_reserved_name $1;
    {binders = PVar $1, []; lhs_type=$2; eq=$3; let_rhs=$4}
  }
| "_" type_annotation? "=" expr {
    {binders = PWild $1, []; lhs_type=$2; eq=$3; let_rhs=$4}
  }
| unit type_annotation? "=" expr {
    {binders = PUnit $1, []; lhs_type=$2; eq=$3; let_rhs=$4}
  }
| record_pattern type_annotation? "=" expr {
    Scoping.check_pattern (PRecord $1);
    {binders = PRecord $1, []; lhs_type=$2; eq=$3; let_rhs=$4}
  }
| par(closed_irrefutable) type_annotation? "=" expr {
    Scoping.check_pattern $1.value.inside;
    {binders = PPar $1, []; lhs_type=$2; eq=$3; let_rhs=$4}
  }
| tuple(sub_irrefutable) type_annotation? "=" expr {
    Utils.nsepseq_iter Scoping.check_pattern $1;
    let hd, tl  = $1 in
    let start   = pattern_to_region hd in
    let stop    = last fst tl in
    let region  = cover start stop in
    let binders = PTuple {value=$1; region}, [] in
    {binders; lhs_type=$2; eq=$3; let_rhs=$4} }

type_annotation:
  ":" type_expr { $1,$2 }

(* Patterns *)

irrefutable:
  sub_irrefutable { $1 }
| tuple(sub_irrefutable) {
    let hd, tl = $1 in
    let start  = pattern_to_region hd in
    let stop   = last fst tl in
    let region = cover start stop in
    PTuple {region; value=$1} }

sub_irrefutable:
  "<ident>"                                              {    PVar $1 }
| "_"                                                    {   PWild $1 }
| unit                                                   {   PUnit $1 }
| record_pattern                                         { PRecord $1 }
| par(closed_irrefutable)                                {    PPar $1 }

closed_irrefutable:
  irrefutable                                            {         $1 }
| constr_pattern                                         { PConstr $1 }
| typed_pattern                                          {  PTyped $1 }

typed_pattern:
  irrefutable ":" type_expr  {
    let start  = pattern_to_region $1 in
    let stop   = type_expr_to_region $3 in
    let region = cover start stop in
    let value  = {pattern=$1; colon=$2; type_expr=$3}
    in {region; value} }

pattern:
  core_pattern { $1 }
| "[" sub_pattern "," "..." sub_pattern "]" {
    let start  = pattern_to_region $2 in
    let stop   = pattern_to_region $5 in
    let region = cover start stop in
    let cons   = {value=$2,$3,$5; region}
    in PList (PCons cons)
  }
| tuple(sub_pattern) {
    let hd, tl = $1 in
    let start  = pattern_to_region hd in
    let stop   = last fst tl in
    let region = cover start stop
    in PTuple {value=$1; region} }

sub_pattern:
  par(sub_pattern)                                       {    PPar $1 }
| core_pattern                                           {         $1 }

core_pattern:
  "<ident>"                                              {    PVar $1 }
| "_"                                                    {   PWild $1 }
| unit                                                   {   PUnit $1 }
| "<int>"                                                {    PInt $1 }
| "<nat>"                                                {    PNat $1 }
| "<bytes>"                                              {  PBytes $1 }
| "true"                                                 {   PTrue $1 }
| "false"                                                {  PFalse $1 }
| "<string>"                                             { PString $1 }
| par(ptuple)                                            {    PPar $1 }
| list__(sub_pattern)                          { PList (PListComp $1) }
| constr_pattern                                         { PConstr $1 }
| record_pattern                                         { PRecord $1 }

record_pattern:
  "{" sep_or_term_list(field_pattern,",") "}" {
    let ne_elements, terminator = $2 in
    let region = cover $1 $3 in
    let value  = {compound = Braces ($1,$3);
                  ne_elements;
                  terminator}
    in {region; value} }

field_pattern:
  field_name "=" sub_pattern {
    let start  = $1.region in
    let stop   = pattern_to_region $3 in
    let region = cover start stop in
    let value  = {field_name=$1; eq=$2; pattern=$3}
    in {region; value} }

constr_pattern:
  "None" { PNone $1 }
| "Some" sub_pattern {
    let stop   = pattern_to_region $2 in
    let region = cover $1 stop
    and value  = $1, $2 in
    PSomeApp {region; value}
  }
| "<constr>" sub_pattern {
    let region = cover $1.region (pattern_to_region $2)
    in PConstrApp {region; value = $1, Some $2}
  }
| "<constr>" { PConstrApp {$1 with value=$1,None} }

ptuple:
  tuple(sub_pattern) {
    let hd, tl = $1 in
    let start  = pattern_to_region hd in
    let stop   = last fst tl in
    let region = cover start stop
    in PTuple {value=$1; region} }

unit:
  "(" ")" { {region = cover $1 $2; value = $1, $2} }

(* Expressions *)

interactive_expr:
  expr_with_let_expr EOF { $1 }

expr:
  base_cond__open(expr) | switch_expr(base_cond) { $1 }

base_cond__open(x):
  base_expr(x) | conditional(expr_with_let_expr) { $1 }

base_cond:
  base_cond__open(base_cond) { $1 }

type_expr_simple_args:
  par(nsepseq(type_expr_simple, ",")) { $1 }

type_expr_simple:
  type_name type_expr_simple_args? {
    let args = $2 in
    match args with
      Some {value; _} ->
        let region = cover $1.region value.rpar in
        let value  = $1, {region; value}
        in TApp {region; value}
    | None -> TVar $1
  }
| "(" nsepseq(type_expr_simple, ",") ")" {
    TProd {region = cover $1 $3; value=$2}
  }
| "(" type_expr_simple "=>" type_expr_simple ")" {
    TFun {region = cover $1 $5; value=$2,$3,$4} }

type_annotation_simple:
  ":" type_expr_simple { $1,$2 }

fun_expr:
  disj_expr_level "=>" expr {
    let arrow, body = $2, $3
    and kwd_fun     = ghost in
    let start       = expr_to_region $1
    and stop        = expr_to_region body in
    let region      = cover start stop in

    let rec arg_to_pattern = function
      EVar v ->
        Scoping.check_reserved_name v;
        PVar v
    | EAnnot {region; value = {inside = EVar v, colon, typ; _}} ->
        Scoping.check_reserved_name v;
        let value = {pattern = PVar v; colon; type_expr = typ}
        in PTyped {region; value}
    | EPar p ->
        let value =
          {p.value with inside = arg_to_pattern p.value.inside}
        in PPar {p with value}
    | EUnit u -> PUnit u
    | ETuple { value; region } ->
        PTuple { value = Utils.nsepseq_map arg_to_pattern value; region}
    | EAnnot {region; value = {inside = t, colon, typ; _}} ->
        let value = { pattern = arg_to_pattern t; colon; type_expr = typ} in
        PPar {
          value = {
            lpar = Region.ghost;
            rpar = Region.ghost;
            inside = PTyped {region; value}
          };
          region
        }
    | e ->
        let open! SyntaxError in
        raise (Error (WrongFunctionArguments e)) in
    let fun_args_to_pattern = function
      EAnnot {
        value = {
          inside = ETuple {value=fun_args; _}, _, _;
          _};
        _} ->
        (*  ((foo:x, bar) : type)  *)
        let bindings =
          List.map (arg_to_pattern <@ snd) (snd fun_args)
        in arg_to_pattern (fst fun_args), bindings
      | EAnnot {
          value = {
            inside = EPar {value = {inside=fun_arg; _}; _}, _, _;
            _};
          _} ->
          (* ((foo:x, bar) : type) *)
         (arg_to_pattern fun_arg, [])
      | EPar {value = {inside = EFun {
          value = {
              binders = PTyped { value = { pattern; colon; type_expr }; region = fun_region }, [];
              arrow;
              body;
              _
          };
          _
        }; _ }; region} ->

        let expr_to_type = function
        | EVar v -> TVar v
        | e -> let open! SyntaxError
            in raise (Error (WrongFunctionArguments e))
        in
        let type_expr = (
          match type_expr with
          | TProd {value; _} ->
            let (hd, rest) = value in
            let rest = rest @ [(arrow, expr_to_type body)]
            in curry hd rest
          | e ->
            TFun {
              value = e, arrow, expr_to_type body;
              region = fun_region
            }
        )
        in
        PTyped {
          value = {
            pattern;
            colon;
            type_expr
          };
          region;
        }, []
      | EPar {value = {inside =  fun_arg; _ }; _} ->
          arg_to_pattern fun_arg, []
      | EAnnot _ as e ->
          arg_to_pattern e, []
      | ETuple {value = fun_args; _} ->
          let bindings =
            List.map (arg_to_pattern <@ snd) (snd fun_args) in
          List.iter Scoping.check_pattern bindings;
          arg_to_pattern (fst fun_args), bindings
      | EUnit _ as e ->
          arg_to_pattern e, []
      | EVar _ as e ->
          arg_to_pattern e, []
      | e -> let open! SyntaxError
            in raise (Error (WrongFunctionArguments e))
    in
    let binders = fun_args_to_pattern $1 in
    let lhs_type = match $1 with 
      EAnnot {value = {inside = _ , _, t; _}; region = r} -> Some (r,t)
      | _ -> None
    in
    let f = {kwd_fun;
             binders;
             lhs_type;
             arrow;
             body
            }
    in EFun {region; value=f} }

base_expr(right_expr):
  disj_expr_level | fun_expr { $1 }

conditional(right_expr):
  if_then_else(right_expr) | if_then(right_expr) { $1 }

parenthesized_expr:
  "{" expr "}" | "(" expr ")" { $2 }

if_then(right_expr):
  "if" parenthesized_expr "{" closed_if ";"? "}" {
    let the_unit = ghost, ghost in
    let ifnot    = EUnit {region=ghost; value=the_unit} in
    let region   = cover $1 $6 in
    let value    = {kwd_if   = $1;
                    test     = $2;
                    kwd_then = $3;
                    ifso     = $4;
                    kwd_else = ghost;
                    ifnot}
    in ECond {region; value} }

if_then_else(right_expr):
  "if" parenthesized_expr "{" closed_if ";"?  "}"
  "else" "{" right_expr ";"? "}" {
    let region = cover $1 $11 in
    let value  = {kwd_if   = $1;
                  test     = $2;
                  kwd_then = $3;
                  ifso     = $4;
                  kwd_else = $6;
                  ifnot    = $9}
    in ECond {region; value} }

base_if_then_else__open(x):
  base_expr(x) | if_then_else(x) { $1 }

base_if_then_else:
  base_if_then_else__open(base_if_then_else) { $1 }

closed_if:
  base_if_then_else__open(closed_if)
| switch_expr(base_if_then_else) { $1 }
| let_expr(expr_with_let_expr) { $1 }

switch_expr(right_expr):
  "switch" switch_expr_ "{" cases(right_expr) "}" {
    let start = $1
    and stop = $5 in
    let region = cover start stop
    and cases = {
      region = nsepseq_to_region (fun x -> x.region) $4;
      value  = $4} in
    let value = {
      kwd_match = $1;
      expr      = $2;
      lead_vbar = None;
      kwd_with  = ghost;
      cases}
    in ECase {region; value} }

switch_expr_:
  par(expr)   { $1.value.inside }
| core_expr_2 {              $1 }

cases(right_expr):
  nseq(case_clause(right_expr)) {
    let hd, tl = $1 in
    hd, List.map (fun f -> expr_to_region f.value.rhs, f) tl }

case_clause(right_expr):
  "|" pattern "=>" right_expr ";"? {
    Scoping.check_pattern $2;
    let start  = pattern_to_region $2
    and stop   = expr_to_region $4 in
    let region = cover start stop
    and value  = {pattern=$2; arrow=$3; rhs=$4}
    in {region; value} }

let_expr(right_expr):
  seq(Attr) "let" ioption("rec") let_binding ";" right_expr {
    let attributes = $1 in
    let kwd_let = $2 in
    let kwd_rec = $3 in
    let binding = $4 in
    let kwd_in  = $5 in
    let body    = $6 in
    let stop    = expr_to_region $6 in
    let region  = cover $2 stop
    and value   = {kwd_let; kwd_rec; binding; kwd_in; body; attributes}
    in ELetIn {region; value} }

disj_expr_level:
  disj_expr
| conj_expr_level { $1 }
| par(tuple(disj_expr_level)) type_annotation_simple? {
    let region = $1.region in
    let tuple  = ETuple {value=$1.value.inside; region} in
    let region =
      match $2 with
        Some (_,s) -> cover $1.region (type_expr_to_region s)
      |       None -> region in
    match $2 with
      Some (colon, typ) ->
        let value = {$1.value with inside = tuple,colon,typ}
        in EAnnot {region; value}
    | None -> tuple }

bin_op(arg1,op,arg2):
  arg1 op arg2 {
    let start  = expr_to_region $1 in
    let stop   = expr_to_region $3 in
    let region = cover start stop
    and value  = { arg1=$1; op=$2; arg2=$3}
    in {region; value} }

disj_expr:
  bin_op(disj_expr_level, "||", conj_expr_level)
| bin_op(disj_expr_level, "or", conj_expr_level) {
    ELogic (BoolExpr (Or $1)) }

conj_expr_level:
  comp_expr_level { $1 }
| bin_op(conj_expr_level, "&&", comp_expr_level) {
    ELogic (BoolExpr (And $1)) }

comp_expr_level:
  bin_op(comp_expr_level, "<", cat_expr_level) {
    ELogic (CompExpr (Lt $1)) }
| bin_op(comp_expr_level, "<=", cat_expr_level) {
    ELogic (CompExpr (Leq $1)) }
| bin_op(comp_expr_level, ">", cat_expr_level) {
    ELogic (CompExpr (Gt $1)) }
| bin_op(comp_expr_level, ">=", cat_expr_level) {
    ELogic (CompExpr (Geq $1)) }
| bin_op(comp_expr_level, "==", cat_expr_level) {
    ELogic (CompExpr (Equal $1)) }
| bin_op(comp_expr_level, "!=", cat_expr_level) {
    ELogic (CompExpr (Neq $1)) }
| cat_expr_level { $1 }

cat_expr_level:
  bin_op(add_expr_level, "++", cat_expr_level)    {  EString (Cat $1) }
| add_expr_level                                  {                $1 }

add_expr_level:
  bin_op(add_expr_level, "+", mult_expr_level)      { EArith (Add $1) }
| bin_op(add_expr_level, "-", mult_expr_level)      { EArith (Sub $1) }
| mult_expr_level                                   {              $1 }

mult_expr_level:
  bin_op(mult_expr_level, "*", unary_expr_level)   { EArith (Mult $1) }
| bin_op(mult_expr_level, "/", unary_expr_level)   {  EArith (Div $1) }
| bin_op(mult_expr_level, "mod", unary_expr_level) {  EArith (Mod $1) }
| unary_expr_level                                 {               $1 }

unary_expr_level:
  call_expr_level { $1 }
| "-" call_expr_level {
    let start  = $1 in
    let stop   = expr_to_region $2 in
    let region = cover start stop
    and value  = {op=$1; arg=$2}
    in EArith (Neg {region; value})
  }
| "!" call_expr_level {
    let start  = $1 in
    let stop   = expr_to_region $2 in
    let region = cover start stop
    and value  = {op=$1; arg=$2} in
    ELogic (BoolExpr (Not {region; value})) }

call_expr_level:
  call_expr_level_in type_annotation_simple? {
    let region =
      match $2 with
        Some (_, s) ->
          cover (expr_to_region $1) (type_expr_to_region s)
      | None -> expr_to_region $1 in
    match $2 with
      Some (colon, t) ->
        let value = {lpar=ghost; inside=$1,colon,t; rpar=ghost}
        in EAnnot {region; value}
    | None -> $1 }

call_expr_level_in:
  call_expr | constr_expr | core_expr { $1 }

constr_expr:
  "None" {
     EConstr (ENone $1)
  }
| "Some" core_expr {
    let region = cover $1 (expr_to_region $2)
    in EConstr (ESomeApp {value=$1,$2; region})
  }
| "<constr>" core_expr {
    let region = cover $1.region (expr_to_region $2) in
    EConstr (EConstrApp {region; value=$1, Some $2})
   }
| "<constr>" {
    EConstr (EConstrApp {$1 with value=$1, None}) }

call_expr:
  core_expr "(" nsepseq(expr, ",") ")" {
    let start  = expr_to_region $1 in
    let stop   = $4 in
    let region = cover start stop in
    let hd, tl = $3 in
    let tl     = List.map snd tl in
    ECall {region; value = $1,(hd,tl)}
  }
| core_expr unit {
    let start  = expr_to_region $1 in
    let stop   = $2.region in
    let region = cover start stop
    and value  = $1, (EUnit $2, [])
    in ECall {region; value} }

common_expr:
  "<int>"                             {               EArith (Int $1) }
| "<mutez>"                           {             EArith (Mutez $1) }
| "<nat>"                             {               EArith (Nat $1) }
| "<bytes>"                           {                     EBytes $1 }
| "<ident>" | module_field            {                       EVar $1 }
| projection                          {                      EProj $1 }
| update_record                       {                    EUpdate $1 }
| "<string>"                          {           EString (String $1) }
| unit                                {                      EUnit $1 }
| "false"                             {  ELogic (BoolExpr (False $1)) }
| "true"                              {   ELogic (BoolExpr (True $1)) }

core_expr_2:
  common_expr   {                   $1 }
| list__(expr)  { EList (EListComp $1) }

list_or_spread:
  "[" expr "," sep_or_term_list(expr, ",") "]" {
    let elts, terminator = $4 in
    let elts = Utils.nsepseq_cons $2 $3 elts in
    let value = {
      compound = Brackets ($1,$5);
      elements = Some elts;
      terminator}
    and region = cover $1 $5 in
    EList (EListComp {region; value})
  }
| "[" expr "," "..." expr "]" {
    let region = cover $1 $6
    and value  = {arg1=$2; op=$4; arg2=$5}
    in EList (ECons {region; value})
  }
| "[" expr? "]" {
    let compound = Brackets ($1,$3)
    and elements =
      match $2 with
        None -> None
      | Some element -> Some (element, []) in
    let value = {compound; elements; terminator=None}
    and region = cover $1 $3 in
    EList (EListComp {region; value}) }

core_expr:
  common_expr
| list_or_spread
| sequence_or_record  {      $1 }
| par(expr)           { EPar $1 }

module_field:
  module_name "." module_fun {
    let region = cover $1.region $3.region in
    {region; value = $1.value ^ "." ^ $3.value} }

module_fun:
  field_name { $1 }
| "or"       { {value="or";  region=$1} }

selection:
  "[" "<int>" "]" selection {
    let r, (hd, tl) = $4 in
    let result: (selection, dot) Utils.nsepseq =
      Component $2, (ghost, hd) :: tl
    in r, result
  }
| "." field_name selection {
    let r, (hd, tl) = $3 in
    let result: (selection, dot) Utils.nsepseq =
      FieldName $2, ($1, hd) :: tl
    in r, result
  }
| "." field_name  {    $1, (FieldName $2, []) }
| "[" "<int>" "]" { ghost, (Component $2, []) }

projection:
  struct_name selection {
    let start  = $1.region in
    let stop   = nsepseq_to_region selection_to_region (snd $2) in
    let region = cover start stop
    and value  = {struct_name = $1;
                  selector    = fst $2;
                  field_path  = snd $2}
    in {region; value}
  }
| module_name "." field_name selection {
    let module_name = $1 in
    let field_name  = $3 in
    let value       = module_name.value ^ "." ^ field_name.value in
    let struct_name = {$1 with value} in
    let start       = $1.region in
    let stop        = nsepseq_to_region selection_to_region (snd $4) in
    let region      = cover start stop
    and value       = {struct_name;
                       selector   = fst $4;
                       field_path = snd $4}
    in {region; value} }

path:
 "<ident>"   { Name $1 }
| projection { Path $1 }

update_record:
  "{""..."path "," sep_or_term_list(field_path_assignment,",") "}" {
    let region = cover $1 $6 in
    let ne_elements, terminator = $5 in
    let value = {
      lbrace = $1;
      record = $3;
      kwd_with = $4;
      updates  = { value = {compound = Braces($1,$6);
                  ne_elements;
                  terminator};
                  region = cover $4 $6};
      rbrace = $6}
    in {region; value} }

expr_with_let_expr:
  expr { $1 }
| let_expr(expr_with_let_expr) { $1 }

sequence_or_record_in:
  expr_with_let_expr ";" sep_or_term_list(expr_with_let_expr,";") {
    let elts, _region = $3 in
    let s_elts = Utils.nsepseq_cons $1 $2 elts
    in PaSequence {s_elts; s_terminator=None}
  }
| field_assignment "," sep_or_term_list(field_assignment,",")  {
    let elts, _region = $3 in
    let r_elts = Utils.nsepseq_cons $1 $2 elts
    in PaRecord {r_elts; r_terminator = None}
  }
| expr_with_let_expr ";"? { PaSingleExpr $1 }

sequence_or_record:
  "{" sequence_or_record_in "}" {
    let compound = Braces ($1,$3) in
    let region   = cover $1 $3 in
    match $2 with
      PaSequence s ->
        let value = {compound;
                     elements = Some s.s_elts;
                     terminator = s.s_terminator}
        in ESeq {region; value}
    | PaRecord r ->
        let value = {compound;
                     ne_elements = r.r_elts;
                     terminator = r.r_terminator}
        in ERecord {region; value}
    | PaSingleExpr e -> e }

field_assignment:
  field_name {
    let value = {
      field_name = $1;
      assignment = ghost;
      field_expr = EVar $1 }
    in {$1 with value}
  }
| field_name ":" expr {
    let start  = $1.region in
    let stop   = expr_to_region $3 in
    let region = cover start stop in
    let value  = {
      field_name = $1;
      assignment = $2;
      field_expr = $3}
    in {region; value} }

field_path_assignment:
  field_name {
    let value = {
      field_path = ($1,[]);
      assignment = ghost;
      field_expr = EVar $1 }
    in {$1 with value}
  }
| nsepseq(field_name,".") ":" expr {
    let start  = nsepseq_to_region (fun x -> x.region) $1 in
    let stop   = expr_to_region $3 in
    let region = cover start stop in
    let value  = {
      field_path = $1;
      assignment = $2;
      field_expr = $3}
    in {region; value} }