Fix incompatibility AST for regexp match in Prism::Translation::Parser

[koic]

This PR fixes the following incompatibility AST for regexp match between Parser gem and Prism:

Parser gem

Returns an match_with_lvasgn node:

$ bundle exec ruby -rparser/ruby33 -ve 'p Parser::Ruby33.parse("/foo/ =~ bar")'
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22]
s(:match_with_lvasgn,
  s(:regexp,
    s(:str, "foo"),
    s(:regopt)),
  s(:send, nil, :bar))

Prism (Prism::Translation::Parser)

Before

Returns an send node:

$ bundle exec ruby -rprism -rprism/translation/parser33 -ve 'p Prism::Translation::Parser33.parse("/foo/ =~ bar")'
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22]
s(:send,
  s(:regexp,
    s(:str, "foo"),
    s(:regopt)), :=~,
  s(:send, nil, :bar))

After

Returns an match_with_lvasgn node:

$ bundle exec ruby -rprism -rprism/translation/parser33 -ve 'p Prism::Translation::Parser33.parse("/foo/ =~ bar")'
ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [x86_64-darwin22]
s(:match_with_lvasgn,
  s(:regexp,
    s(:str, "foo"),
    s(:regopt)),
  s(:send, nil, :bar))

Background

Found due to incompatibility with RuboCop's Performance/EndWith, Performance/StringInclude, and Performance/StartWith` cops.

Note

This is the incompatibility when the receiver is a regular expression literal and =~ is used. Based on the node name :match_with_lvasgn, it appears that Prism's AST becomes more accurate in cases like visit_match_write_node only.

However, as shown in the background, the current behavior of Parser gem is not like this. Considering compatibility with the published AST of Parser gem, the AST incompatibility will be addressed.

This lvar-injecting feature appears to have not been supported by Parser gem for a long time: whitequark/parser#69 (comment)

There seems to be no indication that it will be supported.

This PR prioritizes AST compatibility between the Parser gem and Prism. However, it is unclear whether this is the best approach.

[kddnewton]

I think this is the right approach, prioritizing compatibility. Even though prism is more "right" here, the point is to emit the same AST.