[ruby-core:119740] [Ruby master Bug#20866] Prism assertion when running simplecov with branch coverage and requiring certain code

5 Nov 2024

      Issue #20866 has been updated by alanwu (Alan Wu).

Assignee set to prism

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Bug #20866: Prism assertion when running simplecov with branch coverage and requiring certain code
https://bugs.ruby-lang.org/issues/20866#change-110405

* Author: Earlopain (A S)
* Status: Open
* Assignee: prism
* ruby -v: ruby 3.4.0dev (2024-11-05T13:53:41Z master ed06f018bd) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
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I stumbled upon the following bug report against simplecov: https://github.com/simplecov-ruby/simplecov/issues/1113

I reduced the error down to the following:

```rb
# Gemfile
source "https://rubygems.org"

gem "simplecov"
```

```rb
# test.rb
require "bundler"
require "simplecov"

SimpleCov.start do
  enable_coverage :branch
end

require_relative "external"
```

```rb
# external.rb
def perform_completion
  case @completion_state
  when CompletionState::PERFECT_MATCH
    @dig_perfect_match_proc&.(@perfect_matched)
  end
end
```

```sh
$ bundle exec ruby test.rb
ruby: prism/util/pm_newline_list.c:93: pm_newline_list_line_column: Assertion `cursor >= list->start' failed.
Aborted (core dumped)
```

When running with `parse.y` the error doesn't occur.

-- 
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