From a03f92923b61a64098ea9313f4e70ac3a4553414 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Mon, 4 Mar 2024 21:10:47 +0900
Subject: [PATCH] [ruby/prism] Fix incompatibility AST for regexp match in
 `Prism::Translation::Parser`

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

## Parser gem

Returns an `match_with_lvasgn` node:

```console
$ bundle exec ruby -rparser/ruby33 -ve 'p Parser::Ruby33.parse("/foo/ =~ bar")'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/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:

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

### After

Returns an `match_with_lvasgn` node:

```console
$ bundle exec ruby -rprism -rprism/translation/parser33 -ve 'p Prism::Translation::Parser33.parse("/foo/ =~ bar")'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/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:
https://github.com/whitequark/parser/issues/69#issuecomment-19506391

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.

https://github.com/ruby/prism/commit/dff4abb170
---
 lib/prism/translation/parser/compiler.rb | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/prism/translation/parser/compiler.rb b/lib/prism/translation/parser/compiler.rb
index 0025e4697d7ca5..9dd20baeb4d72a 100644
--- a/lib/prism/translation/parser/compiler.rb
+++ b/lib/prism/translation/parser/compiler.rb
@@ -254,6 +254,10 @@ def visit_call_node(node)
               end
             when :!
               return visit_block(builder.not_op(token(node.message_loc), token(node.opening_loc), visit(node.receiver), token(node.closing_loc)), block)
+            when :=~
+              if (receiver = node.receiver).type == :regular_expression_node
+                return builder.match_op(visit(receiver), token(node.message_loc), visit(node.arguments.arguments.first))
+              end
             when :[]
               return visit_block(builder.index(visit(node.receiver), token(node.opening_loc), visit_all(arguments), token(node.closing_loc)), block)
             when :[]=