I added set definitions by extension.

For example:

const bar : set (int) = set 1; 1+1; f(3); end

AST.ml

@@ -63,6 +63,7 @@ type kwd_patch      = Region.t
 type kwd_procedure  = Region.t
 type kwd_record     = Region.t
 type kwd_remove     = Region.t
+type kwd_set        = Region.t
 type kwd_skip       = Region.t
 type kwd_step       = Region.t
 type kwd_storage    = Region.t
@@ -121,6 +122,7 @@ type fun_name   = string reg
 type type_name  = string reg
 type field_name = string reg
 type map_name   = string reg
+type set_name   = string reg
 type constr     = string reg
 
 (* Parentheses *)
@@ -470,6 +472,16 @@ and expr =
 | ETuple  of tuple
 | EPar    of expr par reg
 
+and set_expr =
+  SetInj of set_injection reg
+
+and set_injection = {
+  opening    : kwd_set;
+  elements   : (expr, semi) nsepseq;
+  terminator : semi option;
+  close      : kwd_end
+}
+
 and map_expr =
   MapLookUp of map_lookup reg
 | MapInj    of map_injection reg
@@ -531,10 +543,6 @@ and list_expr =
 | List      of (expr, comma) nsepseq brackets reg
 | EmptyList of empty_list reg
 
-and set_expr =
-  Set       of (expr, comma) nsepseq braces reg
-| EmptySet  of empty_set reg
-
 and constr_expr =
   SomeApp   of (c_Some * arguments) reg
 | NoneExpr  of none_expr reg
@@ -574,15 +582,6 @@ and typed_empty_list = {
   list_type : type_expr
 }
 
-and empty_set = typed_empty_set par
-
-and typed_empty_set = {
-  lbrace   : lbrace;
-  rbrace   : rbrace;
-  colon    : colon;
-  set_type : type_expr
-}
-
 and none_expr = typed_none_expr par
 
 and typed_none_expr = {
@@ -648,6 +647,9 @@ and map_expr_to_region = function
   MapLookUp {region; _}
 | MapInj    {region; _} -> region
 
+and set_expr_to_region = function
+  SetInj {region; _} -> region
+
 and logic_expr_to_region = function
   BoolExpr e -> bool_expr_to_region e
 | CompExpr e -> comp_expr_to_region e
@@ -685,10 +687,6 @@ and list_expr_to_region = function
 | List      {region; _}
 | EmptyList {region; _} -> region
 
-and set_expr_to_region = function
-  Set      {region; _}
-| EmptySet {region; _} -> region
-
 and constr_expr_to_region = function
   NoneExpr  {region; _}
 | ConstrApp {region; _}
@@ -1138,8 +1136,10 @@ and print_expr = function
 
 and print_map_expr = function
   MapLookUp {value; _} -> print_map_lookup value
-| MapInj inj ->
-    print_map_injection inj
+| MapInj inj           -> print_map_injection inj
+
+and print_set_expr = function
+  SetInj inj -> print_set_injection inj
 
 and print_map_lookup {path; index} =
   let {lbracket; inside; rbracket} = index.value in
@@ -1206,10 +1206,6 @@ and print_list_expr = function
 | List e       -> print_list e
 | EmptyList e  -> print_empty_list e
 
-and print_set_expr = function
-  Set e      -> print_set e
-| EmptySet e -> print_empty_set e
-
 and print_constr_expr = function
   SomeApp e   -> print_some_app e
 | NoneExpr e  -> print_none_expr e
@@ -1265,11 +1261,18 @@ and print_map_remove node =
 
 and print_map_injection {value; _} =
   let {opening; bindings; terminator; close} = value in
-  print_token opening "record";
+  print_token opening "map";
   print_nsepseq ";" print_binding bindings;
   print_terminator terminator;
   print_token close "end"
 
+and print_set_injection {value; _} =
+  let {opening; elements; terminator; close} = value in
+  print_token opening "set";
+  print_nsepseq ";" print_expr elements;
+  print_terminator terminator;
+  print_token close "end"
+
 and print_binding {value; _} =
   let {source; arrow; image} = value in
   print_expr source;
@@ -1298,22 +1301,6 @@ and print_empty_list {value; _} =
   print_type_expr list_type;
   print_token     rpar ")"
 
-and print_set {value; _} =
-  let {lbrace; inside; rbrace} = value in
-  print_token lbrace "{";
-  print_nsepseq "," print_expr inside;
-  print_token rbrace "}"
-
-and print_empty_set {value; _} =
-  let {lpar; inside; rpar} = value in
-  let {lbrace; rbrace; colon; set_type} = inside in
-  print_token     lpar "(";
-  print_token     lbrace "{";
-  print_token     rbrace "}";
-  print_token     colon ":";
-  print_type_expr set_type;
-  print_token     rpar ")"
-
 and print_none_expr {value; _} =
   let {lpar; inside; rpar} = value in
   let {c_None; colon; opt_type} = inside in

AST.mli

@@ -47,6 +47,7 @@ type kwd_patch      = Region.t
 type kwd_procedure  = Region.t
 type kwd_record     = Region.t
 type kwd_remove     = Region.t
+type kwd_set        = Region.t
 type kwd_skip       = Region.t
 type kwd_step       = Region.t
 type kwd_storage    = Region.t
@@ -105,6 +106,7 @@ type fun_name   = string reg
 type type_name  = string reg
 type field_name = string reg
 type map_name   = string reg
+type set_name   = string reg
 type constr     = string reg
 
 (* Parentheses *)
@@ -454,6 +456,16 @@ and expr =
 | ETuple  of tuple
 | EPar    of expr par reg
 
+and set_expr =
+  SetInj of set_injection reg
+
+and set_injection = {
+  opening    : kwd_set;
+  elements   : (expr, semi) nsepseq;
+  terminator : semi option;
+  close      : kwd_end
+}
+
 and map_expr =
   MapLookUp of map_lookup reg
 | MapInj    of map_injection reg
@@ -515,10 +527,6 @@ and list_expr =
 | List      of (expr, comma) nsepseq brackets reg
 | EmptyList of empty_list reg
 
-and set_expr =
-  Set       of (expr, comma) nsepseq braces reg
-| EmptySet  of empty_set reg
-
 and constr_expr =
   SomeApp   of (c_Some * arguments) reg
 | NoneExpr  of none_expr reg
@@ -558,15 +566,6 @@ and typed_empty_list = {
   list_type : type_expr
 }
 
-and empty_set = typed_empty_set par
-
-and typed_empty_set = {
-  lbrace   : lbrace;
-  rbrace   : rbrace;
-  colon    : colon;
-  set_type : type_expr
-}
-
 and none_expr = typed_none_expr par
 
 and typed_none_expr = {

LexToken.mli

@@ -89,6 +89,7 @@ type t =
 | Procedure  of Region.t  (* "procedure"  *)
 | Record     of Region.t  (* "record"     *)
 | Remove     of Region.t  (* "remove"     *)
+| Set        of Region.t  (* "set"        *)
 | Skip       of Region.t  (* "skip"       *)
 | Step       of Region.t  (* "step"       *)
 | Storage    of Region.t  (* "storage"    *)

LexToken.mll

@@ -88,6 +88,7 @@ type t =
 | Procedure  of Region.t  (* "procedure"  *)
 | Record     of Region.t  (* "record"     *)
 | Remove     of Region.t  (* "remove"     *)
+| Set        of Region.t  (* "set"        *)
 | Skip       of Region.t  (* "skip"       *)
 | Step       of Region.t  (* "step"       *)
 | Storage    of Region.t  (* "storage"    *)
@@ -210,6 +211,7 @@ let proj_token = function
 | Procedure  region -> region, "Procedure"
 | Record     region -> region, "Record"
 | Remove     region -> region, "Remove"
+| Set        region -> region, "Set"
 | Skip       region -> region, "Skip"
 | Step       region -> region, "Step"
 | Storage    region -> region, "Storage"
@@ -298,6 +300,7 @@ let to_lexeme = function
 | Procedure  _ -> "procedure"
 | Record     _ -> "record"
 | Remove     _ -> "remove"
+| Set        _ -> "set"
 | Skip       _ -> "skip"
 | Step       _ -> "step"
 | Storage    _ -> "storage"
@@ -355,6 +358,7 @@ let keywords = [
   (fun reg -> Procedure  reg);
   (fun reg -> Record     reg);
   (fun reg -> Remove     reg);
+  (fun reg -> Set        reg);
   (fun reg -> Skip       reg);
   (fun reg -> Step       reg);
   (fun reg -> Storage    reg);
@@ -580,6 +584,7 @@ let is_kwd = function
 | Procedure  _
 | Record     _
 | Remove     _
+| Set        _
 | Skip       _
 | Step       _
 | Storage    _

ParToken.mly

@@ -67,6 +67,7 @@
 %token <Region.t> Procedure   (* "procedure"  *)
 %token <Region.t> Record      (* "record"     *)
 %token <Region.t> Remove      (* "remove"     *)
+%token <Region.t> Set         (* "set"        *)
 %token <Region.t> Skip        (* "skip"       *)
 %token <Region.t> Step        (* "step"       *)
 %token <Region.t> Storage     (* "storage"    *)

Parser.mly

@@ -177,8 +177,15 @@ core_type:
   }
 | Map type_tuple {
     let region = cover $1 $2.region in
-    let value = {value="map"; region=$1}
-    in TApp {region; value = value, $2}
+    let type_constr = {value="map"; region=$1}
+    in TApp {region; value = type_constr, $2}
+  }
+| Set par(type_expr) {
+    let total = cover $1 $2.region in
+    let type_constr = {value="set"; region=$1} in
+    let {region; value = {lpar; inside; rpar}} = $2 in
+    let tuple = {region; value={lpar; inside=inside,[]; rpar}}
+    in TApp {region=total; value = type_constr, tuple}
   }
 | par(type_expr) {
     TPar $1
@@ -405,7 +412,9 @@ unqualified_decl(OP):
              rpar = Region.ghost}
            in EConstr (NoneExpr {region; value})
       | `EMap inj ->
-           EMap (MapInj inj)
+          EMap (MapInj inj)
+      | `ESet inj ->
+          ESet (SetInj inj)
     in $1, $2, $3, $4, init, $6, stop
   }
 
@@ -448,6 +457,7 @@ extended_expr:
                        value  = `EList ($1,$2)} }
 | C_None            { {region = $1; value = `ENone $1} }
 | map_injection     { {region = $1.region; value = `EMap $1} }
+| set_injection     { {region = $1.region; value = `ESet $1} }
 
 
 instruction:
@@ -489,6 +499,18 @@ map_patch:
     in {region; value}
   }
 
+set_injection:
+  Set series(expr) {
+    let first, (others, terminator, close) = $2 in
+    let region = cover $1 close
+    and value = {
+      opening  = $1;
+      elements = first, others;
+      terminator;
+      close}
+    in {region; value}
+  }
+
 map_injection:
   Map series(binding) {
     let first, (others, terminator, close) = $2 in
@@ -797,8 +819,6 @@ core_expr:
 | tuple            { ETuple $1 }
 | list_expr        { EList (List $1) }
 | empty_list       { EList (EmptyList $1) }
-| set_expr         { ESet (Set $1) }
-| empty_set        { ESet (EmptySet $1) }
 | none_expr        { EConstr (NoneExpr $1) }
 | fun_call         { ECall $1 }
 | map_expr         { EMap $1 }
@@ -891,20 +911,6 @@ typed_empty_list:
      list_type = $4}
   }
 
-set_expr:
-  braces(nsepseq(expr,COMMA)) { $1 }
-
-empty_set:
-  par(typed_empty_set) { $1 }
-
-typed_empty_set:
-  LBRACE RBRACE COLON type_expr {
-    {lbrace   = $1;
-     rbrace   = $2;
-     colon    = $3;
-     set_type = $4}
-  }
-
 none_expr:
   par(typed_none_expr) { $1 }
 

Tests/crowdfunding.ligo

@@ -6,7 +6,8 @@ type store is
     funded   : bool;
   end
 
-const foo : store = map "X" -> 10; "Y" -> 11 end
+const foo : map (string, nat) = map "X" -> 10; "Y" -> 11 end
+const bar : set (int) =  set 1; 1+1; f(3); end
 
 entrypoint contribute (storage store : store;
                        const sender  : address;