expression cannot fail

[xiayulu]

Hello, I am using pest parsing markdown. I write the follwing grammar:

What's wrong with my grammar?

[CAD97]

PEG is greedy. Your top-level grammar is inline = { chars | em }.

To parse this, we first try chars = { char* }.

chars will always succeed -- it can match the empty string. Thus the em side of the alternation will never be tried; chars succeeded already.

The simple solution which probably does what you want is to instead use chars = { char+ }, such that chars must match at least one char, and if char fails to match, then inline will continue on to try the next alternation, em.