fix(grainfmt): Group expressions inside array accessors (#1462)

Author: marcusroberts

compiler/src/formatting/format.re

@@ -2454,15 +2454,19 @@ and print_expression =
       Doc.concat([
         print_expression(~original_source, ~comments, expression1),
         Doc.lbracket,
-        print_expression(~original_source, ~comments, expression2),
+        Doc.group(
+          print_expression(~original_source, ~comments, expression2),
+        ),
         Doc.rbracket,
       ])
     | PExpArraySet(expression1, expression2, expression3) =>
       Doc.group(
         Doc.concat([
           print_expression(~original_source, ~comments, expression1),
           Doc.lbracket,
-          print_expression(~original_source, ~comments, expression2),
+          Doc.group(
+            print_expression(~original_source, ~comments, expression2),
+          ),
           Doc.rbracket,
           Doc.space,
           Doc.text("="),

compiler/test/formatter_inputs/arrays.gr

@@ -37,3 +37,5 @@ let addRepeatedGroup = (groupN, state, pos, n, backAmt, callback) => {
     }
   }
 }
+
+export let getBefore = (array, index) => if (array == [>]) "nope" else array[index - 1]

compiler/test/formatter_outputs/arrays.gr

@@ -36,3 +36,6 @@ let addRepeatedGroup = (groupN, state, pos, n, backAmt, callback) => {
     },
   }
 }
+
+export let getBefore = (array, index) => if (array == [>]) "nope"
+else array[index - 1]