Fix some comments disappearing in array sugar.

CHANGELOG.md

@@ -48,6 +48,7 @@ These are only breaking changes for unformatted code.
 - Fix compiler ppx issue when combining `async` and uncurried application https://github.com/rescript-lang/rescript-compiler/pull/5856
 - Fix issue where the internal representation of uncurried types would leak when a non-function is applied in a curried way https://github.com/rescript-lang/rescript-compiler/pull/5892
 - In GenType, check annotations also in module types to decide whether to produce the `.gen.tsx` file https://github.com/rescript-lang/rescript-compiler/pull/5903
+- Fix some comments disappearing in array access expressions https://github.com/rescript-lang/rescript-compiler/pull/5947
 
 #### :nail_care: Polish
 

res_syntax/src/res_comments_table.ml

@@ -1297,6 +1297,17 @@ and walkExpression expr t comments =
     walkExpression operand2 t inside;
     (* (List.concat [inside; after]); *)
     attach t.trailing operand2.pexp_loc after
+  | Pexp_apply
+      ( {pexp_desc = Pexp_ident {txt = Longident.Ldot (Lident "Array", "get")}},
+        [(Nolabel, parentExpr); (Nolabel, memberExpr)] ) ->
+    walkList [Expression parentExpr; Expression memberExpr] t comments
+  | Pexp_apply
+      ( {pexp_desc = Pexp_ident {txt = Longident.Ldot (Lident "Array", "set")}},
+        [(Nolabel, parentExpr); (Nolabel, memberExpr); (Nolabel, targetExpr)] )
+    ->
+    walkList
+      [Expression parentExpr; Expression memberExpr; Expression targetExpr]
+      t comments
   | Pexp_apply (callExpr, arguments) ->
     let before, inside, after = partitionByLoc comments callExpr.pexp_loc in
     let after =

res_syntax/tests/printer/comments/array.res

@@ -0,0 +1,18 @@
+a[ /* zz */ 0 ] =  7 
+
+let _ = (
+  /* zz */ a  
+  )[0]
+
+let _ = (
+  a // zz
+  )[0]
+
+ (
+    incidents
+    ->Belt.Array.keep(({status}) => status === #OPEN)
+    // This comment will vanish 
+    ->Belt.SortArray.stableSortBy((a, b) =>
+      compare(a.createdTime, b.createdTime)
+    )
+  )[0]

res_syntax/tests/printer/comments/expected/array.res.txt

@@ -0,0 +1,12 @@
+a[/* zz */ 0] = 7
+
+let _ = /* zz */ a[0]
+
+let _ = a[0] // zz
+
+(
+  incidents
+  ->Belt.Array.keep(({status}) => status === #OPEN)
+  // This comment will vanish
+  ->Belt.SortArray.stableSortBy((a, b) => compare(a.createdTime, b.createdTime))
+)[0]