Fix duplicated comments in for..of formatter (#8395)

Author: cknitt

CHANGELOG.md

@@ -23,6 +23,7 @@
 #### :bug: Bug fix
 
 - Fix directive `@warning("-102")` not working. https://github.com/rescript-lang/rescript/pull/8322
+- Fix duplicated comments in `for`..`of` formatter. https://github.com/rescript-lang/rescript/pull/8395
 
 #### :memo: Documentation
 

compiler/syntax/src/res_comments_table.ml

@@ -1825,9 +1825,28 @@ and walk_expression expr t comments =
   | Pexp_await expr -> walk_expression expr t comments
   | Pexp_for_of (pattern, expr1, expr2)
   | Pexp_for_await_of (pattern, expr1, expr2) ->
-    walk_pattern pattern t comments;
-    walk_expression expr1 t comments;
-    walk_expression expr2 t comments
+    let leading, inside, trailing =
+      partition_by_loc comments pattern.ppat_loc
+    in
+    attach t.leading pattern.ppat_loc leading;
+    walk_pattern pattern t inside;
+    let after_pattern, rest =
+      partition_adjacent_trailing pattern.ppat_loc trailing
+    in
+    attach t.trailing pattern.ppat_loc after_pattern;
+    let leading, inside, trailing = partition_by_loc rest expr1.pexp_loc in
+    attach t.leading expr1.pexp_loc leading;
+    walk_expression expr1 t inside;
+    let after_expr, rest =
+      partition_adjacent_trailing expr1.pexp_loc trailing
+    in
+    attach t.trailing expr1.pexp_loc after_expr;
+    if is_block_expr expr2 then walk_expression expr2 t rest
+    else
+      let leading, inside, trailing = partition_by_loc rest expr2.pexp_loc in
+      attach t.leading expr2.pexp_loc leading;
+      walk_expression expr2 t inside;
+      attach t.trailing expr2.pexp_loc trailing
   | Pexp_send _ -> ()
 
 and walk_expr_parameter (_attrs, _argLbl, expr_opt, pattern) t comments =

tests/syntax_tests/data/printer/comments/expected/expr.res.txt

@@ -174,6 +174,18 @@ for /* c0 */ i /* c1 */ in /* c2 */ 0 /* c3 */ to /* c4 */ 10 /* c5 */ {
   /* c6 */ doStuff() /* c7 */
 } // trailing
 
+// Pexp_for_of
+for /* c0 */ x /* c1 */ of /* c2 */ xs /* c3 */ {
+  // c4
+  doStuff()
+} // trailing
+
+// Pexp_for_await_of
+for await /* c0 */ x /* c1 */ of /* c2 */ xs /* c3 */ {
+  // c4
+  doStuff()
+} // trailing
+
 // Pexp_pack
 /* c0 */ module(/* c1 */ ModExpr /* c2 */) /* c3 */
 /* c0 */ let /* c1 */ three /* c2 */ = /* c3 */ module(/* c4 */ Three /* c5 */) /* c6 */

tests/syntax_tests/data/printer/comments/expr.res

@@ -176,6 +176,18 @@ for /* c0 */ i /* c1 */ in /* c2 */ 0 /* c3 */ to /* c4 */ 10  /* c5 */ {
   /* c6 */ doStuff() /* c7 */
 } // trailing
 
+// Pexp_for_of
+for /* c0 */ x /* c1 */ of /* c2 */ xs /* c3 */ {
+  // c4
+  doStuff()
+} // trailing
+
+// Pexp_for_await_of
+for await /* c0 */ x /* c1 */ of /* c2 */ xs /* c3 */ {
+  // c4
+  doStuff()
+} // trailing
+
 // Pexp_pack
 /* c0 */ module(/* c1 */ ModExpr /* c2 */) /* c3 */
 /* c0 */ let /* c1 */ three /* c2 */ = /* c3 */ module( /* c4 */Three /* c5 */) /* c6 */