use CoffeeScript.nodes to extract comments

lib/rewriters/coffeescript.js

@@ -4,19 +4,35 @@ import show from 'sanctuary-show';
 import rewrite from '../rewrite.js';
 
 
+function comments(node) {
+  return (
+    Object.values (node)
+    .flatMap (x => {
+      switch (Object.prototype.toString.call (x)) {
+        case '[object Array]':  return x;
+        case '[object Object]': return [x];
+        default:                return [];
+      }
+    })
+    .flatMap (comments)
+    .concat (node.comments ?? [])
+  );
+}
+
 const chunksCoffee = input => {
   const chunks = {literals: new Map ([]), comments: new Map ([])};
-  let number = 0;
-  for (const text of input.match (/^.*(?=\n)/gm)) {
-    number += 1;
-    const match = /^([ \t]*)#(?!##)(.*)$/.exec (text);
-    if (match == null) {
-      chunks.literals.set (number, text);
-    } else {
-      const [, indent, uncommented] = match;
-      chunks.comments.set (number, {indent, number, text: uncommented});
-    }
+  let offset = 0;
+  for (const comment of comments (CoffeeScript.nodes (input))) {
+    const [start, end] = comment.locationData.range;
+    chunks.literals.set (offset, input.slice (offset, start));
+    chunks.comments.set (start, {
+      indent: ' '.repeat (comment.locationData.first_column),
+      number: comment.locationData.first_line + 1,
+      text: comment.content,
+    });
+    offset = end;
   }
+  chunks.literals.set (offset, input.slice (offset));
   return chunks;
 };