Potential Bug? Troubleshooting conflicts when the error message is not helpful

[glyh]

I have my ~90LoC gramar here, with ~30Loc of them being lexer so it's not really that big. I have checked it multiple times but all error message I got when run cargo build is like one of the following:

1. xxx can be reduced to A, but it can also be reduced to A.
2. xxx can have a reduction tree A, but it can also have a reduction tree B, where A is exactly a sub tree of B.

Here's the full error message: https://pastebin.ubuntu.com/p/CT9bRvbHVV/

I am very confused and I'm not sure if this is a bug or not, could someone help me with this? Thanks!

[glyh]

I figured out what this is but the error reporting is very confusing.