Invalid expression: .pat..'$'

[apemost]

environment

• vim: VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Mar 18 2020 18:29:15) Included patches: 1-1453
• OS: Ubuntu 18.04

actual behavior

Error detected while processing function illuminate#on_cursor_moved[1]..<SNR>223_should_illuminate_file[4]..<SNR>223_list_contains_pat:
line    2:
E15: Invalid expression: .pat..'$'
Error detected while processing function illuminate#on_cursor_moved[1]..<SNR>223_should_illuminate_file[4]..<SNR>223_list_contains_pat:
line    2:
E15: Invalid expression: a:val =~# '^'..pat..'$'

expected behavior

No errors.

screen shot (if possible)

[apemost]

Lua offers a string concatenation operator, denoted by "..", but strings can be concatenated with "." in vimscript:

:echo "foo" . "bar"
foobar 

[RRethy]

String concatenation can be done in vimscript with ...

https://vimhelp.org/eval.txt.html#expr6:

For String concatenation ".." is preferred, since "." is ambiguous, it is also
used for |Dict| member access and floating point numbers.

The vim help you linked is for version 7.3.

It seems you are using an early 8.0 version which doesn't have this upgrade in the expression parsing, I'll merge the change, but you need to upgrade your Vim version since many plugins devs (and myself) won't go out of our way to support old version of Vim (5 years old in this case).

[apemost]

Can we add a compatibility check?

Patch 8.1.1114
Problem: Confusing overloaded operator "." for string concatenation.
Solution: Add ".." for string concatenation. Also "let a ..= b".
Files: src/eval.c, src/testdir/test_eval_stuff.vim, runtime/doc/eval.txt

[RRethy]

Compatibility check wouldn't be beneficial since it's adding a lot of logic (check for patch for Neovim and Vim) while the reward is just syntactical.