force comments to start with a space

compiler/fmt/src/spaces.rs

@@ -111,10 +111,16 @@ pub fn fmt_comments_only<'a, I>(
 
 fn fmt_comment<'a>(buf: &mut String<'a>, comment: &'a str) {
     buf.push('#');
+    if !comment.starts_with(" ") {
+        buf.push(' ');
+    }
     buf.push_str(comment);
 }
 
 fn fmt_docs<'a>(buf: &mut String<'a>, docs: &'a str) {
     buf.push_str("##");
+    if !docs.starts_with(" ") {
+        buf.push(' ');
+    }
     buf.push_str(docs);
 }

compiler/fmt/tests/test_fmt.rs

@@ -129,6 +129,24 @@ mod test_fmt {
         );
     }
 
+    #[test]
+    fn force_space_at_begining_of_comment() {
+        expr_formats_to(
+            indoc!(
+                r#"
+                #comment
+                f
+                "#
+            ),
+            indoc!(
+                r#"
+                # comment
+                f
+                "#
+            ),
+        );
+    }
+
     #[test]
     fn func_def() {
         expr_formats_same(indoc!(