Parse error, but still yields a correct AST

[rolandzwaga]

Langium version: 2.1.2 Package name: langium

Steps To Reproduce

1. Check this playground url

Link to code example:

playground url

The current behavior

Check the red squiglies underneath '=#main-title', when mouse-overing it reports the error 'expecting the token EQUALS but found #main-title'. Then check the AST column, the NamedArgument instance has a value of '#main-title'

The expected behavior

I would expect no parsing error to occur, because the AST is exactly what I expect. Of course, I might do something very, very wrong in my grammar, in which case I would really appreciate some guidance.

Thank you in advance!

[spoenemann]

The error is likely due to the way how you defined EQUALS (with positive lookahead). Changing to a simple '=' keyword fixes it:

NamedArgument:
    name=NAME '=' value=Value;

Value returns string:
    STRING | NUMBER | NAME | SELECTOR | BOOL_TRUE | BOOL_FALSE;

Here I also extracted the value to a string typed rule.

[msujew]

Note that there are actually two red squiggles (right after another):

The first one indicates that the = sign couldn't be lexed (due to the issue outlined above by @spoenemann), while the other indicates that EQUALS had to be skipped in order to parse the input.

[rolandzwaga]

Argh, thank you gentlemen, the problem was indeed the defintion of my terminal. The grammar I posted was a simplified version of my real grammar. I now see that I ordered some terminals wrong there. In an effort to try and fix the problem I was trying out all sorts of things and had added the look-aheads. Not realising this actually just made matters worse...

Thank you for your time!