Previously, RubyVM::AST.of opened a wrong file if the iseq's file path is spoofed.
```
module Dummy
binding.irb
end
```
```
$ ruby test.rb
From: test.rb @ line 2 :
1: module Dummy
=> 2: binding.irb
3: end
irb(Dummy):001:0> foo
/home/mame/work/ruby/local/lib/ruby/3.1.0/error_highlight/base.rb:412:in `spot_colon2': undefined method `last_lineno' for nil:NilClass (NoMethodError)
if nd_parent.last_lineno == @node.last_lineno
^^^^^^^^^^^^
```
Found by @kateinoigakukun
This issue is already fixed in the interpreter side.
This change just adds a test for the case.
https://github.com/ruby/error_highlight/commit/f3626b9032
Now the formatter configuration is per Ractor. DefaultFormatter is used
if not set.
DefaultFormatter#message_for is now a class method to allow sub-Ractors
to call the method.
https://github.com/ruby/error_highlight/commit/9fbaa8ab7c
Now, the highlight line is created by replacing non-tab characters with
spaces, and keeping all hard tabs as-is. This means the highlight line
has the completely same indentation as the code snippet line.
Fixes#7https://github.com/ruby/error_highlight/commit/38f20fa542