Refactoring fails badly on some prefix increments #5568

Issue Type: Bug

1. Create a new, empty .c file.

2. Enter this text:

   int main(void) {
       for (int i = 0; i < a->b[i].c; ++i)
       {
           foo();
       }
   }

3. Click on i (any instance of it), then press F2 to begin refactoring.

4. Pick any other name for the variable. (e.g. i2)

5. Refactor preview shows the error: ++i is incorrectly replaced. (e.g. by i2+i)

6. Manually add the erroneous refactor (it's unticked by default) and accept, to confirm that the error shows when the change is actually made.

This breaks even worse when renaming multi-character variable names.

The precise breakage seems to depend on how the variable is used; namely, how "complex" the rest of the line before it is. If I have just a bare ++x, on its own on a line, it works fine. If it's at the end of a for loop, it sometimes breaks, in different ways (which vary further based on... possibly both line length and variable name length? not sure). If it's within a one-line if, it sometimes breaks (again, in various ways -- not sure what the correlation is). However, once I find a breaking scenario, I am able to consistently reproduce it.

Apologies if this has already been raised; with all due respect, I'm not going to trawl through a thousand issues.

Extension version: 0.28.1
VS Code version: Code - OSS 1.44.2 (ff915844119ce9485abfe8aa9076ec76b5300ddd, 2020-04-23T19:32:05.786Z)
OS version: Linux x64 5.4.40-1-MANJARO