Simplifier now emit CONCAT constant

src/passes/2-simplify/pascaligo.ml

@@ -488,8 +488,11 @@ let rec simpl_expression (t:Raw.expr) : expr result =
         String.(sub s 1 (length s - 2))
       in
       return @@ e_literal ~loc (Literal_string s')
-  | EString (Cat _) as e ->
-      fail @@ unsupported_string_catenation e
+  | EString (Cat bo) ->
+    let (bo , loc) = r_split bo in
+    let%bind sl = simpl_expression bo.arg1 in
+    let%bind sr = simpl_expression bo.arg2 in
+    return @@ e_string_cat ~loc sl sr
   | ELogic l -> simpl_logic_expression l
   | EList l -> simpl_list_expression l
   | ESet s -> simpl_set_expression s

src/stages/ast_simplified/combinators.ml

@@ -73,6 +73,7 @@ let e_record ?loc map : expression = location_wrap ?loc @@ E_record map
 let e_tuple ?loc lst : expression = location_wrap ?loc @@ E_tuple lst
 let e_some ?loc s : expression = location_wrap ?loc @@ E_constant ("SOME", [s])
 let e_none ?loc () : expression = location_wrap ?loc @@ E_constant ("NONE", [])
+let e_string_cat ?loc sl sr : expression = location_wrap ?loc @@ E_constant ("CONCAT" , [sl ; sr ])
 let e_map_add ?loc k v old : expression = location_wrap ?loc @@ E_constant ("MAP_ADD" , [k ; v ; old])
 let e_map ?loc lst : expression = location_wrap ?loc @@ E_map lst
 let e_set ?loc lst : expression = location_wrap ?loc @@ E_set lst

src/test/contracts/string.ligo

@@ -1 +1,3 @@
 const s : string = "toto"
+const x : string =  s^"bar"
+const y : string =  "foo"^x

src/test/integration_tests.ml

@@ -262,7 +262,8 @@ let unit_expression () : unit result =
 
 let string_expression () : unit result =
   let%bind program = type_file "./contracts/string.ligo" in
-  expect_eq_evaluate program "s" (e_string "toto")
+  let%bind _ = expect_eq_evaluate program "s" (e_string "toto") in
+  expect_eq_evaluate program "y" (e_string "foototobar")
 
 let include_ () : unit result =
   let%bind program = type_file "./contracts/includer.ligo" in