Add array concat operator

editors/tree-sitter-decodal/grammar.js

@@ -5,11 +5,12 @@ const PREC = {
   OR: 4,
   LOGICAL_AND: 5,
   COMPARE: 6,
-  ADD: 7,
-  MUL: 8,
-  UNARY: 9,
-  CALL: 10,
-  PATH: 11,
+  CONCAT: 7,
+  ADD: 8,
+  MUL: 9,
+  UNARY: 10,
+  CALL: 11,
+  PATH: 12,
 };
 
 function commaSep(rule) {
@@ -192,6 +193,11 @@ module.exports = grammar({
         field('operator', choice('==', '!=', '>', '>=', '<', '<=')),
         field('right', $._expression),
       )),
+      prec.left(PREC.CONCAT, seq(
+        field('left', $._expression),
+        field('operator', token(prec(2, '++'))),
+        field('right', $._expression),
+      )),
       prec.left(PREC.ADD, seq(
         field('left', $._expression),
         field('operator', choice('+', '-')),