Add tuples to the surface language

No helpers to destruct them at the moment

compiler/desugared/from_surface.ml

@@ -588,6 +588,7 @@ let rec translate_expr
     in
     Expr.ematch ~e:(rec_helper e1) ~name:enum_uid ~cases emark
   | ArrayLit es -> Expr.earray (List.map rec_helper es) emark
+  | Tuple es -> Expr.etuple (List.map rec_helper es) emark
   | CollectionOp (((S.Filter { f } | S.Map { f }) as op), collection) ->
     let collection = rec_helper collection in
     let param_name, predicate = f in

compiler/desugared/name_resolution.ml

@@ -315,6 +315,13 @@ let rec process_base_typ
     ( TArray
         (process_base_typ ctxt (Surface.Ast.Data (Mark.remove t), Mark.get t)),
       typ_pos )
+  | Surface.Ast.Data (Surface.Ast.TTuple tl) ->
+    ( TTuple
+        (List.map
+           (fun t ->
+             process_base_typ ctxt (Surface.Ast.Data (Mark.remove t), Mark.get t))
+           tl),
+      typ_pos )
   | Surface.Ast.Data (Surface.Ast.Primitive prim) -> (
     match prim with
     | Surface.Ast.Integer -> TLit TInt, typ_pos

compiler/surface/ast.ml

@@ -55,6 +55,7 @@ and primitive_typ =
 and base_typ_data =
   | Primitive of primitive_typ
   | Collection of base_typ_data Mark.pos
+  | TTuple of base_typ_data Mark.pos list
 
 and base_typ = Condition | Data of base_typ_data
 
@@ -187,6 +188,7 @@ and naked_expression =
   | StructLit of
       (path * uident Mark.pos) Mark.pos * (lident Mark.pos * expression) list
   | ArrayLit of expression list
+  | Tuple of expression list
   | Ident of path * lident Mark.pos
   | Dotted of expression * (path * lident Mark.pos) Mark.pos
       (** Dotted is for both struct field projection and sub-scope variables *)

compiler/surface/parser.mly

@@ -120,6 +120,11 @@ let primitive_typ :=
 let typ_data :=
 | t = primitive_typ ; <Primitive>
 | LIST ; t = addpos(typ_data) ; <Collection>
+| LPAREN ; tl = separated_nonempty_list(COMMA,addpos(typ_data)) ; RPAREN ; {
+  match tl with
+  | [t, _] -> t
+  | ts -> TTuple ts
+}
 
 let typ == t = typ_data ; <Data>
 
@@ -167,7 +172,11 @@ let naked_expression ==
 | l = literal ; {
   Literal l
 }
-| LPAREN ; e = expression ; RPAREN ; <Paren>
+| LPAREN ; el = separated_nonempty_list(COMMA, expression) ; RPAREN ; {
+  match el with
+  | [e] -> Paren e
+  | es -> Tuple es
+}
 | e = expression ;
   DOT ; i = addpos(qlident) ; <Dotted>
 | CARDINAL ; {