Optimize code completion hint range detection

[yangbobo2021]

There is an issue with how the code completion hint range is determined. If the completion range is set incorrectly, the completion suggestions won't be displayed. For example, consider the case a= | + 2; where | represents the cursor position. In this scenario, the completion should suggest a, but if the code completion range is set to an incorrect range, the IDE fails to display the completion suggestion for a. This issue impacts the user experience by not providing relevant suggestions when expected.

Steps to reproduce:

1. Navigate to a code line a= | + 2;.
2. Attempt to trigger code completion at the cursor position.

Expected behavior:

• The completion suggestion for a is displayed.

Actual behavior:

• No completion suggestions are displayed due to an incorrectly set completion range.