[Bug] Text inside heredoc is incorrectly transformed

`def` patterns inside heredoc blocks are incorrectly recognized as method definitions.

```ruby
text = <<EOT
Lorem ipsum
def x(a: String)
Dolor sit amet
EOT
```

In the above code, the text `def x(a: String)` inside the heredoc is being parsed as a method definition.

Text inside heredoc blocks should be skipped during parsing.