add doc for loop label

[Yu-zh]

#382

Need next release to eliminate the warnings.

[peter-jerry-ye-code-review]

‼️ This code review is generated by a bot. Please verify the content before trusting it.

Here are a few observations and potential issues from the provided git diff output:

1. Inconsistent Formatting in continue label Test:

   • In the test "continue label" block, there is a missing space after res = and before outer~:. This inconsistency in formatting could lead to readability issues. It should be let res = outer~: for consistency with other similar constructs in the code.

2. Missing Newline at End of File:

   • The file next/sources/language/src/controls/top.mbt ends with // end match 1 without a newline character. This is indicated by the \ No newline at end of file message in the diff. While this is not a functional issue, it is a best practice to ensure that files end with a newline to avoid potential issues with certain tools and version control systems.

3. Potential Redundancy in break label Test:

   • In the test "break label" block, the else clause with -1 seems redundant because the break outer~ j statement will always execute, ensuring that the else clause is never reached. This could be misleading or unnecessary, and it might be worth considering whether the else clause is needed at all.

These are the key observations from the diff. Addressing these issues can improve code readability and maintainability.