[ruby/prism] Fix an AST and token incompatibility for `Prism::Translation::Parser`

This PR fixes an AST and token incompatibility between Parser gem and `Prism::Translation::Parser`
for dstring literal:

```ruby
"foo
  #{bar}"
```

## Parser gem (Expected)

```console
$ bundle exec ruby -Ilib -rparser/ruby33 -ve \
'buf = Parser::Source::Buffer.new("example.rb"); buf.source = File.read("example.rb"); p Parser::Ruby33.new.tokenize(buf)'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/5124f9ac75) [x86_64-darwin22]
[s(:dstr,
  s(:str, "foo\n"),
  s(:str, "  "),
  s(:begin,
    s(:send, nil, :bar))), [], [[:tSTRING_BEG, ["\"", #<Parser::Source::Range example.rb 0...1>]],
[:tSTRING_CONTENT, ["foo\n", #<Parser::Source::Range example.rb 1...5>]],
[:tSTRING_CONTENT, ["  ", #<Parser::Source::Range example.rb 5...7>]],
[:tSTRING_DBEG, ["\#{", #<Parser::Source::Range example.rb 7...9>]],
[:tIDENTIFIER, ["bar", #<Parser::Source::Range example.rb 9...12>]],
[:tSTRING_DEND, ["}", #<Parser::Source::Range example.rb 12...13>]],
[:tSTRING_END, ["\"", #<Parser::Source::Range example.rb 13...14>]], [:tNL, [nil, #<Parser::Source::Range example.rb 14...15>]]]]
```

## `Prism::Translation::Parser` (Actual)

Previously, the AST and tokens returned by the Parser gem were different. In this case, `dstr` node should not be nested:

```console
$ bundle exec ruby -Ilib -rprism -rprism/translation/parser33 -ve \
'buf = Parser::Source::Buffer.new("example.rb"); buf.source = File.read("example.rb"); p Prism::Translation::Parser33.new.tokenize(buf)'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/5124f9ac75) [x86_64-darwin22]
[s(:dstr,
  s(:dstr,
    s(:str, "foo\n"),
    s(:str, "  ")),
  s(:begin,
    s(:send, nil, :bar))), [], [[:tSTRING_BEG, ["\"", #<Parser::Source::Range example.rb 0...1>]],
[:tSTRING_CONTENT, ["foo\n", #<Parser::Source::Range example.rb 1...5>]],
[:tSTRING_CONTENT, ["  ", #<Parser::Source::Range example.rb 5...7>]],
[:tSTRING_DBEG, ["\#{", #<Parser::Source::Range example.rb 7...9>]],
[:tIDENTIFIER, ["bar", #<Parser::Source::Range example.rb 9...12>]],
[:tSTRING_DEND, ["}", #<Parser::Source::Range example.rb 12...13>]],
[:tSTRING_END, ["\"", #<Parser::Source::Range example.rb 13...14>]], [:tNL, [nil, #<Parser::Source::Range example.rb 14...15>]]]]
```

After this correction, the AST and tokens returned by the Parser gem are the same:

```console
$ bundle exec ruby -Ilib -rprism -rprism/translation/parser33 -ve \
'buf = Parser::Source::Buffer.new("example.rb"); buf.source = File.read("example.rb"); p Prism::Translation::Parser33.new.tokenize(buf)'
ruby 3.3.0 (2023-12-25 revision https://github.com/ruby/prism/commit/5124f9ac75) [x86_64-darwin22]
[s(:dstr,
  s(:str, "foo\n"),
  s(:str, "  "),
  s(:begin,
    s(:send, nil, :bar))), [], [[:tSTRING_BEG, ["\"", #<Parser::Source::Range example.rb 0...1>]],
[:tSTRING_CONTENT, ["foo\n", #<Parser::Source::Range example.rb 1...5>]],
[:tSTRING_CONTENT, ["  ", #<Parser::Source::Range example.rb 5...7>]],
[:tSTRING_DBEG, ["\#{", #<Parser::Source::Range example.rb 7...9>]],
[:tIDENTIFIER, ["bar", #<Parser::Source::Range example.rb 9...12>]],
[:tSTRING_DEND, ["}", #<Parser::Source::Range example.rb 12...13>]],
[:tSTRING_END, ["\"", #<Parser::Source::Range example.rb 13...14>]], [:tNL, [nil, #<Parser::Source::Range example.rb 14...15>]]]]
```

https://github.com/ruby/prism/commit/c1652a9ee7

1 files changed, 18 insertions, 2 deletions

diff --git a/lib/prism/translation/parser/lexer.rb b/lib/prism/translation/parser/lexer.rb
index 9cf86476ba..7febca449e 100644
--- a/lib/prism/translation/parser/lexer.rb
+++ b/lib/prism/translation/parser/lexer.rb
@@ -295,8 +295,24 @@ module Prism
               unless (lines = token.value.lines).one?
                 start_offset = offset_cache[token.location.start_offset]
                 lines.map do |line|
-                  end_offset = start_offset + line.length
-                  tokens << [:tSTRING_CONTENT, [line, Range.new(source_buffer, offset_cache[start_offset], offset_cache[end_offset])]]
+                  newline = line.end_with?("\r\n") ? "\r\n" : "\n"
+                  chomped_line = line.chomp
+                  if match = chomped_line.match(/(?<backslashes>\\+)\z/)
+                    adjustment = match[:backslashes].size / 2
+                    adjusted_line = chomped_line.delete_suffix("\\" * adjustment)
+                    if match[:backslashes].size.odd?
+                      adjusted_line.delete_suffix!("\\")
+                      adjustment += 2
+                    else
+                      adjusted_line << newline
+                    end
+                  else
+                    adjusted_line = line
+                    adjustment = 0
+                  end
+
+                  end_offset = start_offset + adjusted_line.length + adjustment
+                  tokens << [:tSTRING_CONTENT, [adjusted_line, Range.new(source_buffer, offset_cache[start_offset], offset_cache[end_offset])]]
                   start_offset = end_offset
                 end
                 next